Acetylene, Propane, Mapp and Oxygen Gases – Torches, Hoses, Regulators, Setup

 Please see my disclaimer page.

The following information is based on my own experiences and research and is for informational use only.  Your reliance on any of this information is at your own risk!

Author:  Nancy LT Hamilton

Last edited:  2/9/24, 4/25/22, 10/10/21, 8/12/21, 7/31/21, 7/29/21, 7/28/21, 3/22/18, 2/23/17

On the following pages, you’ll find a lot of information about Acetylene gas, tanks, hoses, and regulators.  But there is also information about Mapp gas, oxygen, and propane, as well as information on torches, hoses, regulators, and setups related to these gases.

See my new video (as of 4/25/22) on the oxygen concentrator:



What is acetylene?

Acetylene is a gas that is colorless, odorless, and lighter than air.  While it might try to be stealthy, with its colorless/odorless nature, no one will likely miss its explosive nature, for acetylene is a highly explosive gas.  Acetylene is sensitive to shocks and likes to explode violently. To control its explosive nature, it is stored in specially designed cylinders and mixed with other things like acetone.

Acetylene is used for soldering/welding/cutting and was used for running the lights on motorcycles and buses, as we shall see! Acetylene is a hot gas that can burn at temperatures of up to 6,300 °F/3,480 °C.  Watch those fingers! Ouch!

History of Acetylene and the Acetylene Tank

Talk about a hazardous job.  This probably beats crab fishing as one of the most dangerous occupations!

  •  In 1896, two French scientists, Georges Claude and Albert Hess, discovered that acetone can “dissolve many times its own volume of acetylene” ( “History: Acetylene dissolved in acetone”).  The acetylene is mixed with Acetone and then poured into a porous mass. The theory is that “an explosion cannot spread in a tube with a diameter of a fraction of a millimeter”.  Claude and Hess worked to find a way to make compressed acetylene gas less volatile.
  • The original porous material that they used developed voids in its structure, and the acetylene gas filled the voids and exploded. It must have been a frightening research subject!


In 1906,  (Nils) Gustaf Dalén found a solution.   “Numerous unsuccessful attempts were made to prepare such a porous mass which would be sufficiently resistant and elastic to withstand the shocks encountered in transportation, without cracking and crumbling and thus producing cavities filled with explosive acetylene gas.” (Nobel Lectures, Physics 1901-1921).

In his presentation speech on December 10, 1912, Professor H.G. Söderbaum (President of the Royal Swedish Academy of Sciences at the time) discussed Dalén’s discovery: “By a complicated and carefully developed process, this substance is enclosed in steel containers which thus become practical accumulators for the acetylene gas. The porous mass in the container is half-filled with acetone, and acetylene is then introduced by compressing it to a pressure of ten atmospheres. Under this pressure and at a temperature of 15° C, the container contains one hundred times its own volume of acetylene. The container is then ready to supply to a lighthouse or light-buoy the acetylene necessary for lighting.” (Nobel Lectures: Söderbaum, H.G.)

Nowadays, Gustaf’s porous material – a mixture of diatomaceous earth and asbestos (perhaps, also cement and charcoal. See Air products’ page, Safetygram-13, under “Filler Material”), called  Aga.  Aga is still in use today.

Calcium silicate is often used as a replacement for asbestos.  Other chemicals/chemical compounds used are silica lime, charcoal, and other materials.  The idea is to have a lightweight yet porous surface to contain the gas.  The proportions of the materials are controlled by the Department of Transportation (DOT) in the USA.  This is to ensure that the material doesn’t crack even with rough use.  If a crack forms, the gas and/or acetone can accumulate in it and explode.

Acetylene is still being mixed with Acetone and sometimes mixed with (DMF) Dimethylformamide.

On a personal note, Gustaf became the managing director of AGA in 1909 (Nobel “Gustaf Dalén”).  In 1912, Gustaf was blinded while testing acetylene tanks.  He continued to work (at Aga) and invent until his death in 1937.  Gustaf was contracted to provide the lighting for the Panama Canal.

One of Gustaf’s many inventions was a flashing apparatus for lighthouses (around 1907).  The apparatus used a liter of acetylene to produce 10,000 small flashes.  This drastically reduced the amount of acetylene that lighthouses needed to use because they didn’t have to burn continuously.  In 1907, Gustaf also created the Sun Valve.  A simple, ingenious little switch that turned off the acetylene (in the lighthouse) during the day and back on at night.  No one believed that a device that simple could work.  The patent office insisted on a demonstration before approving the patent application.  It’s a pretty cool little mechanism.  Check out Aga’s page on the Aga Saga.

Safety precautions for acetylene gas

Talk to a professional

Notice:  Before setting up any torch system for the first time, consult with a professional at a bottled gas supplier like Airgas (USA), Praxair (USA), Calor (UK), Flogas (UK), Elgas Stargas (Australia), etc.  If you are still unsure of what to do, ask an experienced torch user to help you set up.

leaking-acetylene-tank-Vancouver-car  Plumber’s car explosion.  A leaking acetylene tank, an enclosed space, an electronic car lock, and BOOM!  (Image from the Vancouver Sun Plumber’s car explodes in Vancouver’s West End by Tiffany Crawford. May 22, 2013.)


The point of my scare tactics is that you should never leave your acetylene tanks in your car!  Don’t store them in enclosed spaces like closets, cabinets, and lockers!  Also, check for leaks BEFORE bringing them into your car or your home/studio/office/shop, etc. It is recommended that you don’t store tanks in your home.  Check with your insurance company and any applicable organization (housing association, fire department, landlords or managing agencies, etc.) as to whether you are, in fact, allowed to have the tanks on the property and if any damage is covered in case of a fire or explosion.

In case of an acetylene fire

If you have an out-of-control gas leak or fire:  IF you can and it is safe!!!!, turn off the gas, and then leave the area.  Call 911 (in the USA). Alert them to the nature of the problem:  “I have an acetylene gas leak, or I have an acetylene fire”.  They have specific gas handling practices.  Don’t put your rescuers’ lives in jeopardy.  If you are in another country and don’t know the emergency number, here is a list of emergency numbers around the world.  If there is a person who is trained in handling acetylene fires, they can, if possible AND safe, shut off the gas.

If you have a small fire at one of the fittings on the torch AND If it is safe to do so, turn off the gas and immediately apply a wet rag to the fire.  Leave the building and call 911.  The heat from the fire could cause the plugs (see further on for more about plugs) on the top and bottom to blow – expelling large amounts of gas and or flames. This occurs at only 212°F (100°C)!!! (Information from Air Products, Safetygram – 13)

Note:  the following (in brackets) should only be done by a professional trained in managing acetylene fires. 

{Acetylene fires can be put out with dry powder or carbon dioxide fire extinguishers. If other tanks are nearby, water them down to keep them cool. Why?  Keep reading…

Here’s a quote from Air Products’ PDF (see Required Reading for link) that should blow (pun intended) your socks off:

“The fusible metal plugs at the top and bottom of the cylinder will melt at 212°F. If the fusible metal plugs relieve, flames can be projected approximately 15 feet from the top and bottom of the cylinder. “

*For information on safe handling and other very important procedures for Acetylene and other gases, including oxygen, please see Air Products Safetygrams.

Fun facts about acetylene

Well, maybe not fun…but important!

  • A full tank of acetylene has a pressure of 250 psig (pounds per square inch gauge).  PSIG is a comparison of the pressure around the gauge (the pressure on the earth) with the pressure in the tank. Most people (myself included) abbreviate it to psi.  Now, to get really confusing, there is another measurement of pressure:  psia.  Psia measures pressure relative to a vacuum.  A vacuum has 0 pressure (think deep space). The atmospheric pressure on our planet is generally 14.7;  it varies a little depending on where you are.   So, if, for some insane reason, you wanted to measure the absolute pressure in your acetylene tank (ASIA), the formula would be: (psig of the tank + 14.7 psi = Asia of the tank).  Here it is in numbers:  250 psig plus the 14.7 atmospheric pressure = 264.7 psia.  Got it?  Suffice it to say that your regulator measures in PSIG, often abbreviated as PSI.
  • Never set your regulators higher than 15 psi(g) for Acetylene when soldering or doing anything else!  NEVER EVER!!!  What else are you doing with that tank?  Filling balloons is not a great idea, you know?   Sorry, I gave you this idea.  DO NOT FILL BALLOONS OR ANYTHING ELSE WITH ACETYLENE OR OTHER EXPLOSIVE GAS!


  • Just remember the Hindenburg.  (To be honest, that was Hydrogen Gas.  But, the point is the same: don’t play with highly flammable, explosive gases – ever).
  • Acetylene is lighter than air – but not as light as helium, so stop thinking about balloons!  You’d blow yourself up, you know, or set your studio on fire!
  • garlic  Acetylene gas has been treated with a chemical to make it smell like garlic.  In its “wild” state, it is odorless.
  • In the United States, acetylene cylinders are marked with DOT-8 or DOT-8AL.  This means that the tank has been made according to the Department of Transportation’s (Dot) specifications for acetylene. See Virginia Tech’s website, under Cylinder Labeling, to see more information on this.
  • I only open my tank about a quarter of a turn (2″ – 3″).  This also makes it faster and easier to shut the tank off.
  • Shut the tank off at the stem using one of your tank keys.
  • Please see the In case of an acetylene fire section of this site for further information in case of a leak or fire. Sorry to repeat this, but it is important.  In case of fire, AND if it is safe to do so,  shut off the gas.  Call the fire department after you leave the building. Don’t forget to let the other residents of your home/studio/shop in on the situation!  Please do your homework on what to do in case of fire, have a plan in place, and don’t have a fire in the first place!  Check out some of the many sources I’ve listed here for more information. Please read this page:  Emergency Response to Acetylene Cylinders by

The Nevers

  • Never set the psi on your acetylene regulator higher than 15 psi.  NEVER!
  • Never let your tank run empty, especially when using it with oxygen.  Oxygen can backpressure into the tank and cause an explosion. Also, debris from the bottom of the tank can clog hoses, cylinders, and torch tips. Another reason: depending on the age of the tank, the acetone that the acetylene is mixed with becomes syrupy over time and can clog things up.  If your gas smells funny or burns weirdly, stop using it!  Who knows what you are burning (and inhaling)?
  • Never use your tank while it is on its side. If your tank has been on its side, let it stand upright for anywhere from 1/2 hour to 24 hours (see above).
  • Never let your tank freeze; Acetone and acetylene can separate – clogging hoses and potentially blowing you up.
  • Never store your tank in a location where it could be exposed to excessive heat.  Like, don’t put it on top of your kiln.
  • Never modify or repair tanks.
  • Never leave your acetylene tank in your car.
  • Never throw, drop, or abuse your tank. (See, I told you!)
  • Never stand in front of your regulator when turning on the tank.  The regulator can explode from the front or the back, so stand to the side.
  • Never fill your tank yourself – well, of course, if you work for a compressed gas company (or own one) and are trained and authorized to fill tanks, fill away!
  • Never use oil or grease on your regulators or fittings.  In the presence of oxygen, they are flammable.
  • Never use a cracked, burned, or crushed hose.  Replace it immediately.
  • Never use any other type of hose with acetylene besides the type made specifically for acetylene. Acetylene hoses have gas-specific safety precautions built into them.
  • Never lift your tank by the valve cap or stem.
  • Never use your regulator as a lifting or carrying handle.  Hold the tank itself – not the regulator.  You could bend or snap off the relatively thin connection to the tank.
  • Never use a regulator designed for one type of gas with another, i.e., don’t use a propane regulator on an acetylene tank or vice versa.  Bad idea. The exception to this is a disposable gas tank system; you can switch Mapp gas for propane and vice versa. See the Mapp Gas/Propylene Gas section of this page.
  • Never store your cylinders in an enclosed area.
  • Never use plumber’s tape to fix leaky regulators or hoses.  Tape should never be used to fix a gas leak.  Instead, the regulator should be serviced or tightened further. Leaking means the fittings aren’t tight enough or are damaged.
  • Never – Leave pressure on a regulator, hose, or torch when not in use for an extended period of time.  The system should be purged of gas after use.

More information about acetylene gas

Chemical compound formula: C2H2.

Acetylene is a gas composed of 92.2% (by weight) carbon (C2) and 7.8% hydrogen (H2). The reason that the gas burns so hot is because of the mix of carbon and hydrogen. Acetylene is distributed in cylinders or tanks in a dissolved (in acetone), liquid state.  Acetylene tanks can not (by law and common sense) be filled with any other type of gas.

Acetylene is basically an unstable gas in that it likes to explode.  So, to combat its socially reprehensible behavior, besides storing it in special cylinders, it is mixed with acetone or DMF.

Acetone, According to the CDC (Centers for Disease Control), “Acetone may cause adverse health effects following exposure via inhalation, ingestion, or dermal or eye contact.” I recommend not aiming the torch at your face.

Dimethylformamide (DMF) information from the CDC states that the chemical is readily absorbed by the skin and can cause liver damage and other health risks. Getting old is hard enough on those vital organs, so I’d avoid contact with Dimethylformamide!

The acetylene gas cylinder

Problems with gas cylinders and what to do – leaking acetylene cylinders, regulator problems, etc.

  • If, when you get your new tanks (before the regulators are installed), and the stem or valve is leaking, don’t bring it inside! Did you check this before bringing it into the house?  If not, and it’s leaking, bring it back outside. Call the dealer for pickup.  Be sure to tell them that the tank is leaking.
  • This recently happened to me: The system was all set up and working fine.  One night, as I was closing shop, I shut off the tank and drained my hose.  I noticed that the inlet regulator was still indicating pressure.  What to do? I wanted to scream and run around in circles, but instead, I had my amazingly strong and handsome husband (just in case he ever reads what I write) remove the whole setup from the studio, plop it outside, and then I called the dealer. “Please pick this stupid cylinder up and bring me a non-leaking one right now!”  (Well, that’s almost what I said.)  Here are my recommendations on what to do if you experience the same situation:
    • Take the tank and regulators outside.
    • Call the dealer for a pickup.  Don’t forget to tell them that the tank is leaking.
    • If you are a nervous Nellie like I am, leave the regulators on the cylinder, then wait until the delivery person shows up.
    • If leaving the equipment on, be sure that the outlet pressure gauge is open (counterclockwise). (By open, we mean that no gas is reaching the regulators.  This can be counterintuitive as “open” actually means that the gas does not flow into the regulators.) You want to avoid gas in the hoses and torch handle.
    • Double-check that the torch is completely shut off, too!
    • Remember to snatch your regulator, torch, hoses, and key/wrench back from the delivery person – before they run off with them! You will probably have to disassemble the unit yourself, leaving you exhausted and with little strength left for a delivery truck chase.
  • If the gas cylinder/tank is on and there is any fluctuation in the inlet gauge or the outlet gauge AND you are not using the gas, shut off the tanks, move the cylinder – with attached regulators – outside, and call the dealer. They will advise you as to whether it is safe to remove the gauges or not.  This is probably a problem with your gauges – but you should check with a pro.  Don’t forget:  The pressure WILL fluctuate (on both gauges but mostly on the outlet gauge (the one that controls gas to the hose and torch) when you are soldering.  This is because the gas level is being lowered because you are burning it up!
  • At Chimera Art’s Jewelry Studio, which I am co-manager of, we often have issues with gas leaking into the regulator even after the system is shut down.  I believe that the problem is that people won’t shut the valve tightly enough to close it fully. So, check that your tank is fully shut down.  If you can’t manage it by hand, use a tank wrench.

Recently, I learned that acetylene tanks and pressurized gases are required to have PRDs (Pressure Release Device).  I’m going to let the US Department of Transportation’s Pipeline and Hazardous Materials Safety Administration (whew!) explain what that is:

“What is a PRD?  A pressure amd/or temperature activates device used to prevent the pressure from rising above a predetermined maximum to prevent rupture of a normally charged container when dubject to a standard fire.”

What to do if you drop your gas cylinder

  • If you drop your acetylene tank – especially on a hard surface – call your supplier first. The tank is most likely fine.  Let it sit upright for two hours or so, though.   I just spoke with Airgas, and they said that there shouldn’t be any problems, as the tanks are made to handle abuse. He told me that he dropped a tank off of the truck onto the tarmac of the parking lot, and it was fine (I hope I didn’t get that one!).
  • If you drop your acetylene tank with the regulators attached, go through the checklist below before lighting the torch, and also follow the recommendations above. Ensure that your regulators are working!
  • If you drop your oxygen, propane, or other tanks with (or without) the regulators attached, I’d go through the following checklist and ensure that none of the conditions listed exist.  If any of these conditions are present, purchase new ones or get the components repaired. Call your gas dealer, and don’t use your torch until it is repaired. The tank itself should be fine. See below.

Checklist after dropping a gas cylinder

  • Check your hoses for evidence of cracks, burns, crushing, etc. Look for signs of damage with your regulators:  broken glass, bent connections, big dings. Check your tanks to ensure that there are no holes, crushed areas, folds, bent stems, dings, etc.  If any of these conditions exist, don’t turn on the gas. Have a gas professional like Airgas or Praxair stop by to pick up the tank.
  • Chain your tank(s) to the wall or put it (them) into a cart NOW!  Dropping your tanks twice doesn’t make you look too good and is certainly not a recommended practice. (See the section below for how to attach your gas tanks to a wall).
  •  If everything looks fine AND you had a little chat with your gas dealer, I’d check all connections for leaks one more time.  It’s fun.  It is.  Really.
  • Open the inlet gauge only (meaning, open the tank so that gas runs into the regulators using the tank key), check for leaks, then open the outlet gauge (meaning allowing the gas to enter the hose and torch by turning the valve/T), and check for leaks.  If all looks good, light the torch.  Watch the gauges.  Test the system.  Turn it all off and watch to ensure that the gauges and the tank are working as they should. Now, have a lie-down.
  • Remember:  I am not responsible for any injuries or damages that may occur from any advice presented here.  I am not a gas professional. Jeweler, yes; gas professional, nope.  In all cases, I recommend that you check with a gas professional!!! I mean it!

Cylinder Pressure Readings Vs. Actual Contents for Oxygen and Acetylene

The relationship between your cylinder’s contents and what the psi is in the tank varies with the gas.  Oxygen has a direct correlation between contents and pressure:  a full tank of oxygen, at 70°F,  (244 cf) shows a pressure of about 2200 psi. At half full, an oxygen tank will read half the pressure and will contain approx. Half the contents of a full cylinder, i.e., 1100 psi pressure reading with 122cf left in the cylinder. Oxygen tank pressure varies by about 4% for every 20°F.

Acetylene, on the other hand, is less precise: a full tank at 70°F will show the pressure at about 250 psi. But, the pressure reading can jump up or dip down, depending on the temperature.  If it’s 90°F in your studio (get a fan!), you’ll appear to have more gas if you go by the regulator (315 psi). But at 50 degrees F, you’ll appear to have less than 190 psi.

 The acetylene cylinder

Untitled-5  The parts of a tank setup. (And a lovely drawing, to boot.)

For the History of the tank, see the above heading.

*Note here!  When you buy your compressed gas tanks or oxygen tanks, you don’t keep that shiny new canister.  When you bring your tank in for filling, they take yours and give you a filled bottle.  I will bet that it will be nowhere near as pretty as your brand-new one is, but that’s the way it works.  Stop using your tank before your gauge indicates that you are out of gas (notice:  I said BEFORE you are out of gas!). Acetylene, in a “B” cylinder, usually runs somewhere around $35.00 plus delivery.

Compressed gasses are supplied in cylinders, also called bottles. I am fond of calling them “tanks”.  They are made from either steel or aluminum. Acetylene cylinders are made from steel (with an Aga core).

The cylinders come in a range of sizes and types. There are many different adaptors available if your torch setup doesn’t fit your tank. adapter  You should consult with a professional gas supplier on what adaptors to purchase. There are adaptors for hoses, regulators, etc.  If your Smith Little Torch (Amazon) doesn’t seem to fit onto your B tank, know that there is an adaptor for it. Buying in kits often eliminates the use of adapters.

The size of the adapter will depend not only on the type of gas you are using but also on the size of your gas cylinder and the type of torch you are using.

  This is from the Miller-Smith Little Torch PDF.

Make sure that your intake outlet matches the intake valve on your regulators.  Here’s my chart:  Compressed Gas Valve Outlet Sizes.

Safeopedia (you’ll hear a lot from them in this article) says this about your acetylene tank, “Pressure-relieving mechanisms are built into the cylinders by the manufacturer that allows them to vent when exposed to high temperatures. This can fuel a surrounding fire in some cases, but it helps prevent explosion of the cylinders with the release of all their contents and the associated pressure and shrapnel.”

Inside an acetylene tank

inside-tank  Here’s the inside of an acetylene tank.  This porous filler (usually “Aga) is used to help stabilize the volatile gas.

“Acetylene can be safely compressed up to 275 psi (they don’t mean you can turn your regulator up that high!) when dissolved in acetone and stored in specially designed cylinders filled with porous material… These porous filler materials aid in the prevention of high-pressure gas pockets forming in the cylinder.” * From Fundamentals of Professional Welding, Sweethaven Publishing.

Acetylene Tank Sizes


W-Line Tanks – John Ward from the Kings of Welding has shared his chart on gas cylinder sizes that includes information on the W-Line tank. This is a line of tanks that pretty much starts with a W – except for the B and MC tanks.  I do not know why!  Tanks in the W-Line series:  WTL,  WK, WS/WSL, WC, WQ, B, and MC.

   BTW, if you are a welder or not, you might want to check out the Kings of Welding‘s site.

  (Image from, The History of Four-cylinder Motorcycle Engines in America by Paul Garson. Note the acetylene tank on the handlebars – sideways too!) (Photos by Paul Garson and Teddy Pieper).

MC: 13.2″ (34 cm) tall, 7 lbs (3.2 kg), maximum gas capacity: 10 ft3 (.3 m3). Smaller than a B tank. The “B” tank got its name because it was used on buses to supply a source of fuel to run the bus’s lights.  MC tanks were mounted on the handlebars of a motorbike to run their lights.  Can you imagine cruising along with a live bomb between your arms and right below your face on a motorcycle?  Shudder, shudder!

B:  19.5″ (49 cm) Ht., 22 lbs (10 kg), maximum gas capacity:  40 ft3 (1.1 m3) I have a B tank.  It’s not too heavy to lift yet and has enough gas to last me many months.  The B tank holds 40 cubic feet of gas.

WQ: 22.5″ (57 cm) Ht., 34 lbs (16 kg), maximum gas capacity:  60 ft3 (1.7 m3).

WC: 33.1″ (84 cm) Ht., 87 lbs (39 kg), maximum gas capacity:  111 ft3 (3.1 m3).

That’s enough – we’ve already gone way past my lifting ability.  There are other (bigger and heavier) tanks:

  • WS/WSL
  • WK
  • WTL

There are also A-Line tanks in sizes 3, 4, and 5.  Weights range from 41 lbs (19 kg) to 350 lbs (9.9 kg). Whoa, big boy!

  Contenti has a chart on tank types and their fittings (what size the connection to the tank is) which is very helpful.

 The stem of an acetylene tank

Thanks to my buddy Tom, who knows a lot of stuff, for the image below:


As Tom recommends, also test the valve for leaks.  Tom’s drawing illustrates where to test. On a personal note, I have had three tanks with leaking stems in the past year!

valve-stem 1

Acetylene tanks should only be opened a couple of inches – maybe 2″-3″.  Definitely don’t open it more than 1 1/2 turns. I open mine about 1/8th of a turn.  You’ll know if it’s open enough – your flame will burn well.

Acetylene flame temperatures

Acetylene mixed with oxygen burns at 3,480°C (6,296°F).  When mixed with air, it burns at 2,500°C (4,532°F).  It is the third hottest gas after Cyanogen and Dicyanoacetylene. Acetylene’s range for combustion with oxygen to ignite is from 2.5% to 100% (according to the MSHA).

*Note: The Department of Mineral Mining (Virginia) states that the temperature that Acetylene and Oxygen burn is 5700 degrees F.  Without O2, they list 4600 Degrees F.  So, who knows? It’s hot either way!

*** I give up searching for the “facts”.  It seems that each of the several sources that I referenced has something slightly different to say.  The message is clear to me,  no matter what the numbers:   Acetylene is hot and flammable.  The end (of my research on this topic – for now).

Gas cylinder tools, fittings, regulators, and more

Tank wrenches for opening, closing, adding, and removing fittings

To open/close your gas stems and connections, you can use an adjustable wrench or a universal tank wrench.  But, for opening the cylinder valve, if it doesn’t have a knob, use a Tank Key only!  They’re cheap – keep a few on hand.

  Use a tank key with this type of stem.  Wrenches can strip the stem – making it difficult to shut off in an emergency.

  Lucky you!  No tank key is needed.

tank-wrench Universal Tank Wrench

adj-wrench Adjustable Wrench – very different from a Pipe Wrench.  Don’t use a pipe wrench.  Its teeth can damage the brass connections on your regulator.

tank-key Tank Key

The gas supplier is usually responsible for tank inspection BUT ( this is a big BUT) you MUST TEST THE TANK, yourself, FOR LEAKS:  check the stem and the place where the stem is attached to the cylinder (valve) before bringing it into your home, garage or studio. Haven’t I already said this?  I guess it’s important, or I’m losing it (again).

The Regulator

Regulators are used to regulate the pressure that is present in compressed gas cylinders.  They also show you how much gas you have in the cylinder.  You never want to use acetylene or oxygen without a regulator.

In order to increase pressure on your torch, you’ll want to use a regulator – for whatever type of gas you are using.

Regulator Types: Stages

Regulators come in three basic types:  three-stage, dual-stage, and single-stage. The stages are internal, so a dual gauge regulator is not necessarily a two-stage regulator. But, I have yet to find a two-stage, single gauge regulator.  If you know of one, let me know!  Basically, the dual-stage regulator supplies a more constant delivery pressure, while a 1 stage regulator may require adjustment during (especially long-term) use. The three-stage can handle high supply pressure (up to 3000 psi) and provides a stable, low output pressure.

If you are using gas in a cylinder with gradually decreasing pressure, it is best to use a dual-stage regulator to keep the pressure steady.

Single-stage regulators are much cheaper, but unless you do short-term soldering tasks, the pressure will fluctuate, especially as the gas in the tank gets depleted. You will be fiddling with controls!  I know that I prefer a dual-stage regulator for metalsmithing, and I believe glass bead makers do too.

Here’s a little video from NeonControls on YouTube to explain the difference between single and dual-stage regulators.

single-stage-goss-acetylene-regulator  This is a single-stage regulator from Goss. As you can see, it only shows the amount of gas/pressure in the cylinder.  But, it is self-regulating. The pressure goes from 2-15 psi for acetylene. To increase the amount of gas, you open it up more. The pressure fluctuates as the level in the cylinder decreases. I do not like using this type of regulator because the flame tends to be uneven and fluctuates in size.  These are great in group situations, though, or for studios where you don’t want inexperienced people accidentally setting your acetylene regulators to the “Kill” setting – over 15 psi!

smith-regulator  There are also flow regulators similar to those found with a small disposable system.  Miller Smith makes such a system with their Little Torch for disposable tanks, product #23-1014.  These regulators adjust the amount of gas entering the line without gauges.

The Terminology, Construction, And Functions Of Regulators

acetylene-regulator-3  A dual-stage acetylene regulator.

inlet-gauge  The Inlet/high pressure/operating pressure Gauge (pick a name – any name!)

The Cylinder Pressure Gauge (CPG)

Aka: the high-pressure gauge, the operating pressure dial, the inlet pressure gauge, etc.

The Cylinder Pressure Gauge measures the pressure at the tank/cylinder.  It is the dial on the right side of a double regulator. It regulates the pressure of the gas coming from the tank and allows you to see how much gas is in the tank.

  • To shut off the gas at the tank (as measured by the inlet gauge), pull/turn the key/knob in a clockwise direction.  After shutoff, the gauge should read 0.  It shouldn’t fluctuate.  As discussed earlier, there may be an issue with your regulators or the cylinder.  Do not use it!
  • Remember: don’t stand in front of the regulators when turning on the gas – stand to the side. Regulators have a safety valve, and if the pressure gets too high, it can blow.  Also, the front and back of the regulator may blow out.  I’ve never seen this or heard of it happening, personally, but I believe those trusted sources that say this is possible!
  • To open the tank, turn in a counterclockwise direction.
  • Propane and Oxygen tanks close in the same manner.
  • Oxygen and Acetylene cylinders should be “cracked” before hooking up the regulators. Open both the oxygen and acetylene cylinders for a second.  Do them one at a time and wait a few seconds before opening the next cylinder – just to be super safe.  O2 likes to help things burn. The process of cracking the cylinder blows out any crud or dirt present in the valve outlet so that it doesn’t get in the regulator. Wipe the exterior of the outlet after closing the valve.  Be sure to use a clean, oil or grease-free cloth.
  • For fuel gases, like propane and hydrogen, just wipe out the valve with a dry cloth. Do not “crack” the valve, as the gas may ignite from friction or other heat sources, and the hydrogen can catch fire just from the pressurized release.

outlet-regulator The outlet/working pressure/low-pressure gauge.

 The Working Pressure Gauge (WPG)

Aka: The low-pressure gauge and the outlet pressure gauge, etc.

The outlet pressure gauge allows you to adjust the amount of gas/pressure entering your hose and torch handle.  Turn it down for less gas and up for more.  Don’t forget: Never go over 15 psi on acetylene!  Sorry about the repetition, but it’s important!

  • If shutting down your system, after shutting off the gas at the tank, release the diaphragm on the regulator and stop the flow of gas to the hose and torch.  To do this, turn the bar/knob counterclockwise.  Release the gas in the hose and in the torch by either opening the torch or opening and lighting the torch (recommended method). The pressure should now return to 0.

  My regulator for acetylene.    Note that these Victor regulators have a knob instead of the bar that mine has.

  • To allow gas to flow, turn the bar/knob clockwise until you see the pressure climb to 10 to 15 psi for acetylene.

For more information, check out these sources:

Checking For Leaks

  • Never, ever, never, ever use plumber tape to fix a leak or a loose connection!  If you detect a leak, Turn off the gas, drain the line – without lighting the gas – and re-tighten the connection.  Turn on the gas and check again (see the soap test in the following paragraph and probably in 10 other places on this page.  I get confused, you know).
  • Make your first check with only the inlet gauge activated (turning on the gas at the tank).  If there are no leaks, then tighten the outlet gauge and check all connections related to it.
  • leak-checks  Check all connections that are not solid pieces with a mixture of dish soap (2 parts) and water (1 part). Very, very gently stir the soap and water – you don’t want to make bubbles.  Paint the soapy mixture on the connection, wait, and watch.  If there is no bubbling action, move to the next connection.  leak-testing  (Gas leaking from a connection.  Photo from Virginia Tech.
  • You might want to wash off the soap with a damp rag afterward.
  • Check the hose connections at the flashback arrestor on the regulator (you do have one, right?).   check-leaks-at-torch-and-hose  Now, check the hose connection at the torch handle for leaks.  Inspect the hose while you’re at it.  Ensure that the torch head is tight, too.

Some notes on Regulators and Tanks

  • Never use grease, lubricants, or oils on any part of your torch, tank, hose, or regulator – especially with oxygen:  oxygen likes to blow up when in contact with oil or grease.
  • *Note: Turn off the gas, drain your hoses, and bring your regulators in for servicing if you have any issues with your regulators (i.e., popping, unusual fluctuations, weird behavior). If you are mobile with your tank, i.e., taking your tank to job sites, you should be especially vigilant because your regulators, hoses, and tanks are experiencing much more wear and tear.  If you use them outside, sunlight and weather can further degrade your system. Use T hoses whenever possible.
  • Always get used regulators checked out.  Chances are, they need to be refurbished.  It doesn’t cost much (maybe $35.00 or so), and it is SOOO worth having a safe torch and a long life. See the car explosion images above for cost-effectiveness.  Speak with your gas supplier on when to schedule maintenance.
  • You can use an Acetylene regulator with LPG gases, BUT you can’t use an LPG regulator on an Acetylene tank. See Smith Equipment FAQ below.
  • Oxygen regulators should only be used with oxygen and should never be used for fuel gases.  Gases can contaminate the regulators.

For Further Research on Regulators:

The gas cylinder

“Oxygen and fuel gas cylinders should be stored separately by at least 20 feet, or separated by a barrier of at least five feet that can resist fire for a half hour.” From Safeopedia.

How to identify what’s in your gas cylinder


There are several markings on your tank.  They can be used as clues as to what’s in your cylinder.  You can also check its last inspection date if you so desire. Cylinder Identification – Adding Up the Clues is a good page to familiarize yourself with these markings. In Europe, you can read this:  British Compressed Gases Association. In Canada?  Transport Canada has this information on cylinders.

See also:

Traveling with your gas cylinders (especially acetylene)

I spoke with Airgas today about my inability to find any Department of Transportation (DOT) information on transporting a single “B” acetylene tank in a private motor vehicle.  Now, I know why.  Boy, did I waste many, many hours on this one?  According to Airgas, there are no laws (in California) against transporting cylinders weighing less than 1000 lbs in your car, van, or pickup truck.  There are no federal laws against the transportation of a few cylinders containing explosives/liquids or other gases a jeweler would use. DOT’s laws kick in at 1000 lbs (Type 2, I believe), but I’m not getting into commercial transportation – beyond my scope of experience and definitely well beyond my level of interest in this subject!

gas-cylinder-cap  If you use cylinders larger than “B” or “C”, you should ensure that the caps are in place.  The smaller B and C cylinders don’t come with caps (at least not at Airgas or Praxair – to my knowledge).  BTW, don’t carry your tanks by the stem.

So, if there’s no law against transporting the cylinder in your car, why won’t they carry them to your car?  Well, as with most things in this litigious country, it’s so that they don’t get sued for damaging, dirtying, or otherwise messing up your car – not because it’s against the law!  They will carry the tanks to your pickup truck’s gate, though.  But, you have to put them in the truck and secure them.  Alas, there are so many forums and so much misinformation.  Unless, of course, Airgas is wrong.

If you know of any Federal laws prohibiting this practice, please contact me!

There are probably state regulations that you should be aware of.  So, check those out.  Apparently, in California, there are no regulations against traveling with your little tanks. Check with your local, county, and state laws.

There are regulations against traveling with refilled one-pound propane cylinders – those that are not designed for refilling.  There is a $500,000 fine plus five years of prison time for doing so.   Make sure that your cylinders are DOT legally and lawfully refillable and transportable. 

Below are common sense suggestions for transporting gases in your vehicle.  But first,  check your city’s/county’s/state’s/country’s laws before transporting any gases.  You are responsible for your decisions and actions when transporting gases!

  • Bring a little testing kit with you and test the cylinder at the store for leaks. I’ve had to return several tanks due to leaks.
  • Keep the windows open (at least in the back seat).
  • Don’t transport in any fashion that could cause the stem to break off or become damaged.
  • It’s preferable to transport gases secured in the back of an open trailer or truck bed.
  • No refillable tanks unless they are DOT-approved for transport.
  • Don’t smoke anything.
  • Don’t leave the tank in the car.
  • Don’t travel with the regulators attached.
  • Don’t get into a fiery car crash.
  • Don’t lay a tank on its side.  (See below).
  • If in the interior of a car, ensure that the tank doesn’t flop around, slide, or fall over.   Wedge “stuff” around it so that it is immovable. If possible, strap it in place.
  • In a truck or van, strap the cylinder (in at least two points) to the walls of the vehicle.  If you cannot do that, lay it flat and ensure that it won’t slide around – at all!  Maybe pick up the tanks after a good Costco shop and wedge them in with the cases of beer and boxes of groceries? Don’t forget to let it stand upright for 2-24 hours.
  • Have the gas dealer pick up any leaking tanks.  Don’t transport those – PLEASE!

Obviously, the safest route, to you at least, is to have the supplier deliver the tanks to your home.  It’s easier, too.  They pick up the empty cylinder and give you a not-so-shiny, not-brand-new one – but it’s full of gas, and you don’t have to stress all the way home!  Just don’t forget to check the cylinder valve on your new tank to ensure that it is not leaking before the driver drives off.  This has happened to me twice! Of course, it costs extra.

One more reason to travel with your tanks upright and secured.  Another bon mott from Safeopedia, “Any significant mechanical shock to an acetylene cylinder means it should be re-tested because internal damage (particularly to the porous medium) may not be apparent but creates voids where decomposition can occur, thus creating an explosion risk.”

Keeping Tanks Upright

Acetylene cylinders should not be on their sides for more than a few moments.  Transporting acetylene cylinders on their sides is not recommended, nor is it safe.  Always, always, allow the tank to stand for at least 7 hours or up to 24 hours. The danger in a tank lying on its side is that pure acetylene can accumulate near the valve stem and drain out of the aga.  Also, there’s a chance that the acetylene and the acetone will separate. * Information from Virginia Tech.  But, we’ve already covered this I think.  It’s all starting to blur together…One more – Safeopedia says this, “tanks shouldn’t be stored on their side because doing so allows the liquid acetone to enter the valves and may cause damage”

Further notes on keeping your acetylene tank upright from **Fundamentals of Professional Welding, Sweethaven Publishing:

“Acetone is a liquid chemical that dissolves large portions of acetylene under pressure without changing the nature of the gas. Being a liquid, acetone can be drawn from an acetylene cylinder when it is not upright. You should not store acetylene cylinders on their side, but if they are, you must let the cylinder stand upright for a minimum of 2 hours before using. This allows the acetone to settle to the bottom of the cylinder.”

*Note:  In the quote above, they state that a cylinder should sit for a minimum of two hours.  I’ve read that the time to keep it upright before using it is anywhere from “a few minutes” to 24 hours, so it’s up to you what to do.  I’d aim for 24 hours – especially if you don’t know how long it has been on its side.  But, what is known is that the tank needs to be in an upright position for a while before use. I think the time for the tank to sit upright may have something to do with the amount of time that it spent on its side, but I’m not positive about this!  Err on the side of caution!

OSHA states that: “When cylinders are transported by powered vehicles, they shall be secured in a vertical position.” 1926.350(a)(5)

See EIGA’s page for European regulations.

Gas cylinders and heat

Gas cylinders are not designed for temperatures above 125°F (52°C).  So, leaving them in a closed car in the Mojave desert in mid-summer is not the best choice.  Actually, I was in Death Valley one summer when it was so hot that IF I had had a tank in the car, it probably would have exploded. It was 126 degrees F at Furnace Creek, Death Valley.  We (sis and I) stupidly got out of our vehicle to see what being that hot was like. We decided it wasn’t really that much fun and got back in the tankless car.  The hottest it has ever been (so far) in the world was recorded in Death Valley (reliably recorded?) at 134.1°F (56.7°C).  However, Aziziya, Libya, might contest that.  For 90 years, they were the leaders in hot as F… places, but they were decertified in 2012  (BTW, the temperature was 136.0 °F (57.8 °C ).  Wikipedia says this about the highest temperatures.  (I’m not sure why it is taking so long to certify these temperatures.)

“There have since been higher readings of 54.4 °C (129.9 °F) in August 2020 and July 2021, both at Furnace Creek, that are pending validation.”

It has probably been hotter in Death Valley (and Libya), but no one was around (lived?) to record it!   Glad we missed that day because, you know, my sister and I would have gotten out of the car! Interestingly, there are actually “heat tourists”.  Who knew?  Back to the topic at hand!  Read more at Guinness World Records.

Fixing gas cylinders for storage

Attach your acetylene tank to a stable object at two points – don’t secure anything to the stem or regulators – there’s a risk that, if the tank falls, it can snap off the stem or the regulators.  I use a heavy chain, but I just read that it should be an insulated chain.  Whoops. You can also use straps to secure it to the wall or a heavy piece of furniture.  Don’t use bungee cords. See my illustration of an acetylene tank for the location of the chain or straps on the tank.  Don’t forget to make the chain/strap removable, or you’re going to have a lot of fun when it’s time to refill the tank!  I use clips like these (see below) to make it safe and removable.

carabiner-clip Carabiner Clip  – for clipping the chain to the “O” hooks screwed into the wall. Mine are 2″ long.

Screw-eye Eyebolts:  The one I use is about 3 1/8″ X 3/4″.

Here’s my setup:

acetylene-tank-safe-storage Chained at two points to my cabinets.

According to OSHA: “1910.253(b)(2)(ii)

Inside of buildings, cylinders shall be stored in a well-protected, well-ventilated, dry location, at least 20 (6.1 m) feet from highly combustible materials such as oil or excelsior. Cylinders should be stored in definitely assigned places away from elevators, stairs, or gangways. Assigned storage spaces shall be located where cylinders will not be knocked over or damaged by passing or falling objects, or subject to tampering by unauthorized persons. Cylinders shall not be kept in unventilated enclosures such as lockers and cupboards.

Rio Grande has this to say about tank storage:

“Store all fuel and oxygen tanks safely in an appropriate carrier or securely chain them to a wall to reduce the risk of valve damage that could potentially cause a dangerous release of compressed gas.”

Additional equipment for safe welding and soldering with gases

The flashback arrestor

You can purchase arrestors for the torch end and for the regulator. That said, the safest setup is to have flashback arrestors on the torch side of things, as most flashback explosions occur in the hose.  Some torches have built-in flashback arrestors, so they may not be necessary. You may still need a check valve, though.  Check with the manufacturer as to whether your torch has one or both.  You DO NOT want to have a flashback arrestor on the torch and the tank!  This can restrict the flow of the gases and cause additional problems.

flashback-arrestor   These flashback arrestors are for the torch end.

smith-flashback-arrestor These Smith flashback arrestors are for the regulator. Not recommended. It’s best to locate the flashback arrestors on the torch.

Flashback Arrestors restrict the backward flow of gases and flame (from reaching the pressurized, explosive gas in the cylinder!).  There is also a “flame barrier” in the arrestor that keeps the flame from going any further.

The Smith brand Silver Smith (TM) torch (for hobbyists and jewelers) or their Handi-Heet (TM) torch (Industrial)* do not need flashback arrestors or check valves at the torch handle – according to Smith.  Double-check that both flashback arrestors and check valves are included.

Here’s a good video of how flashback arrestors work by BOC:  Keeping Safe With Flashback Arrestors.

Here’s an article on flashback arrestors: A Commentary On Backfires, Flashbacks and Flashback Arrestors by David Gaily at Harris, A Lincoln Electric Company, discussing the differences between the torch-mounted and regulator-mounted.

What are flashbacks

PLEASE read this from David Pryor, Director of Engineering at Victor Technologies.

Flashback is caused when gases mix in either the fuel side or the oxygen side.  One of the gasses can reverse and go into the other side of the torch.  This can happen when there is too much pressure in the system for the size of the torch tip being used. It can also happen if the tip is dirty, the gas supply is low, the tip is dirty, or there is another operator error.

When the fuels cross, this new mixture can move through all parts of the system:  torch, hose, regulators, and tanks.  If the gas ignites, you are in trouble!  Use check valves and flashback arrestors to avoid these depressing events!

Check Valves

Check Valves stop the backflow of gases but not flames. Check valves are usually installed at the back of the torch.  You should have both check valves and flashback arrestors on the back end of your torch. 

The following quote is from David Pryor of Victor Technologies on check valves.

“When fuel gas backs into the oxygen line or oxygen backs into the fuel gas line, the mixture can travel through the torch, into the hose, through the regulator, and possibly into the supply cylinder or system. This condition represents a very dangerous situation if the gases ignite. Reverse-flow check valves (Figure 1a) at the torch help reduce the possibility of reverse gas flow. However, these valves are mechanical devices and may malfunction if they are not maintained properly.”

What are backfires

Let’s quote David again on the subject of Backfires! (The Importance of Exercising OxyFuel Welding Safety, Feb. 10, 2009)

Two of the most common incidents in oxyfuel welding and cutting are backfire (and sustained backfire) and flashback. A backfire occurs when the velocity of fuel gas, burning at the tip with the support of oxygen, is reduced to a point where it is less than the burning rate and backfires into the tip or torch, usually to where the fuel gas and oxygen are mixed. This is often very audible, especially if you’re using large multiflames. The noise is created by the flame backfiring into the mixer. Sometimes the backfire continues to burn in the mixer area, supported by the flow of fuel gas and oxygen. This event, called sustained backfire, generally is accompanied by a loud whistle noise.”

Welding and soldering hoses

The hose is one of the weakest links in any gas/air/oxygen scenario.  They age, crack, leak. Hot metal can burn holes in it. Chemicals can corrode them. As discussed above, there can be flashbacks in them or a situation where fuel/oxygen can mix, causing serious dangers if they ignite.  Pay attention to your hose.  I check mine every time I use it.  Hoses are NOT always interchangeable between gases.  NEVER use anything but an acetylene hose with acetylene.

  • Check your hoses every day for wear and tear.
  • Replace hoses every four years. *
  • Keep the hose away from sparks and flame.
  • Keep the hose away from the pickle, flux, hot metal, hot solder, chemicals, and your feet.
  • Red is for gas.  Green is for oxygen.
  • Replace burnt, cracked, or damaged hoses immediately.  NEVER use a damaged hose!
  • Oxygen and fuel gas hoses are NOT interchangeable.
  • There are three basic connection types for hoses:  A, B & C.   A is for low volume, and B is for O2, Acetylene, and Propane medium volume.  C, as is probably apparent by now, is for high gas volume.
  • 02 hoses are green, and the gas hoses are red.  oxygen-and-acetyelene-hose  Forney acetylene and 02 hose. Black hoses are for inert gasses.

The material the hose is made from needs to be compatible with the gas that it carries.  This is to avoid degradation of the hose and resulting hazards.

Here’s an article from Rexarc on hose types and which hose goes with which gas.

What gases to use with which grades of hose:

  • Acetylene – use only R, RM, or T grades.  R and RM grades can only be used with Acetylene.
  • Most Fuel gases (including Acetylene and Propane) – use T grade.

Hose Grades – details

  • R grades – the cover and the interior tube are not oil or flame-resistant.  When exposed to oil, the hoses can get gummy and degrade.
  • RM grades – the cover IS flame resistant, but it is not oil resistant. When exposed to oil, the hoses can get gummy and degrade.
  • T Grades – flame and oil-resistant.  The cover is self-extinguishing.  There are T grades that have been made even safer by making thicker covers to prevent flying slag and dragging from damaging the hose. They are called welding and scarfing hoses.  T grades are more expensive than R or RM.

Always bleed your hoses if not in use for 30 minutes or more to extend their life and reduce risk.

The Torch

See my pages on Torches.  Torches, What Torch to Buy, and Torch/Gas Questions.

The torch is the final stage in controlling the amount of gas that is used.  You can adjust the size of your flame and the amount of heat generated by adjusting how open the torch is.


  • Don’t use handles designed for other gases.  Use propane equipment with propane, acetylene equipment with acetylene, etc.
  • Don’t switch torch tips, i.e., don’t use a Goss tip with a Smith handle.  I had an experience while I was in school getting my jeweler’s certificate that scared the hell out of everyone involved. I wanted to change to a smaller torch tip and grabbed one from the box of tips. When I lit the torch, a ball of fire shot out of it.  My quick-thinking friend, David, turned off the gas supply immediately, probably saving me from serious injury and protecting those around me. The fireball left a black handprint on the wall where the flame (complete with soot) blew over my hand.  Ugh!  Amazingly, I didn’t get burnt!
  • Don’t light your torch with a cigarette lighter or matches – use a striker (electronic or manual). Want burned hands?

What’s inside the oxygen/acetylene torch?

This:  inside-a-oxygen-gas-torch

This is a very simplified illustration of what happens in the oxy/gas torch.

With a gas/air system, the surrounding air is pulled into the mixing chamber (or mixing head).  smith-silversmith-torch-tip  The Smith Silversmith torch tip has holes to facilitate the intake of air.  My Goss has an air intake area that sucks in air. goss-torch-head

Torch Tips

This part is just not done.  My neck hurts, and my feet are numb, so I’m quitting for now.  With any luck, I’ll remember to come back and finish this section!  You need a lot of luck and perhaps a memory, too. Actually, my memory is so bad that I didn’t realize until this moment that I have another page I’m working on, which is about torches.  Geez… I guess I won’t work on this section anymore!  Check out my Torch Page to continue this discussion.

You’re going to need a torch tip for that torch!  What you are doing will determine the size of the tip.  If you are welding together an exact replica of the Statue of Liberty,  statue-of-liberty please use a large torch tip.  If you are soldering prongs for a setting, let’s think a bit smaller.

Each torch has a set of torch tips designed specifically for use with it. Don’t use tips from another type of torch.  Did you read what happened to me? If not, please go back and read my tale under The Torch (above).


As mentioned earlier, if you are soldering gargantuan pieces of jewelry, you might want a third, larger tip.  Also, large tips come in handy for refining metal.  Some even use two torches to solder large pieces.  The Little Torch has the Rosebud tip (or the heating tip) and the twin flame tip.  Check out the Miller Welds Little Torch Page.

Torch tip numbers and sizes are NOT consistent across torches.  A #3 Little Torch tip is way, way smaller than, for instance, a Goss #3.  It goes without saying (right?) that you don’t use tips that weren’t designed for your torch!!!

In summary (at least for today), have 2-3 tips around for a variety of uses. That said, I basically use just one tip most of the time.  It’s the Smith Little Torch number seven tip.  I adjust the gas and oxygen to create a variety of flame types.

Using your system

Starting Up Your Torch

Please see my and Chimera Art’s video on the safe use of an acetylene torch and tanks.  In it, I show you how to turn on your gas, regulators, and torch, plus how to turn it all off again! Very important safety information is covered.  Acetylene/air setup.  (Image from Virginia Tech: Compressed Gas Cylinders Equipment.)

Stand to the side of the regulators when turning on the gas and adjusting the outlet and inlet pressure.  There is a very remote chance that the regulator will blow out. The only images that I found on ye olde interweb were the one above and this one from Air Products EXCELLENT PDF (read it). I also didn’t find any stories about this happening.  So, I guess it doesn’t happen too often but, why play with fire (so to speak). What can happen is that the gas can leak into the regulators.  Acetylene, when allowed to collect in a contained space, is extremely volatile and is eagerly waiting for a small spark to create a big blow. See exploding car photos and the photo above for evidence of this fact.


  • When first turning on your tank, check that the diaphragm is open on the Outlet (left side of the regulator – see below) FIRST! If it isn’t, drain the gas from the hose by opening the torch, lighting the gas, and burning off the excess (for gas/air systems only). Check that gauges are reset to zero (like in the image above).
  • Now, turn on the gas with the key or the torch wrench.  Push the key/wrench backward in a counterclockwise movement – a quarter of a turn or 2″-3″.
  • The first time you open your tank, it might be very, very tight.  You might need to find a strong man or woman to open it for you.  After the initial opening, just turn the tank off by tightening it by hand. To ensure that you shut it tightly enough, check the gauges – after draining the hoses – the gauges should read zero. When tightening:  remember, you don’t want to call someone for help every time you turn on the gas!  There is a balance between too tight and not tight enough.  An indicator of your effectiveness at shutting it off is the gauges remaining at zero.  If the gauge slowly starts to move, it’s not shut completely.  It might take a few hours for this to occur, so check a few hours later. Movement within the regulator means you have gas leaking into them. It’s not a safe situation. I would check often during your first few days of use – until you start to understand your system fully. If you don’t have the strength to turn the cylinder off, you will need help.   Perhaps look into a different type of key or wrench or get a tank with a knob.
  • On initial opening: I recommend that you “crack” the cylinder before putting on your regulators. This cleans out any gunk/debris that is in the tank that could clog the regulators. Then, using hand strength only, reclose the cylinder and set up the regulators.  Opening the tank first, before the regulators are in place, allows extra room for leverage. It also discourages ole’ Bruto (your overly macho cousin) from using the regulators as part of that leverage.  We don’t want undue pressure on our regulators; they can bend or worse – snap off!
  • gauge-inlet-open-outlet-shut  Moving on: You should now see the gauge go up, on the right, but still be at zero on the left – as in the photo above. Tighten the regulator adjusting screw (the turning thingy may be a knob or a bar), clockwise, to allow the gas to flow to the hoses. Turn until the pressure on the outlet regulator measures 10 – 15 psi. Do this slowly and watch where the needle moves on the dial.  I may have said this 50 times, but I’ll say it again: Never, ever go past 15 psi!  Ever!  Acetylene regulators have two sets of numbers.  Usually, you want to read the inside numbers to set your pressure.  Use whichever numbers have the red warning lines at 15 psi.    See the Never Section on this page. If you accidentally go too far (don’t do that – take your time), turn your regulator clockwise and release a little gas by opening the torch handle for a second. Check the gauges: Are they stable? No dropping or rising of pressure?  Great! You’re set and ready to start soldering!
  • Wait:  no long, dangly sleeves, long hair tied up, protective glasses  –  IR type, cats cleared out of the area? Of course!  Close-toed shoes? Check. Ventilation in place? Check, check. Fire retardant/proof surface in place? Yup. All flammables removed from the area?  Yes, mother.  Okay, GO! Light that torch and solder something!


Inlet and outlet pressure are open and are just waiting for you to start soldering!

On the terminology and myriad names for these gauges, I like the inlet and outlet pressure terms because they are simple and clear: inlet measures the gas coming in from the tank, and the outlet measures the gas going out of the tank!  Violá!

Special Information

  • Gas Regulators (left-hand threads – grooved fittings) are threaded in the opposite direction as those for Oxygen tanks (right-hand threads – smooth fittings) – that’s so you don’t try to put the wrong regulator on the wrong type of tank.  Did you completely ignore the red and green coloring system? Perhaps you aren’t having the best day? Don’t worry; it would be tough for you to screw this up.  But, if it’s that bad of a day, perhaps you shouldn’t be soldering.

Using Your Gas/O2 System

Victor Oxygen Regulator
  • To shut off a gas/O2 torch, turn off the oxygen first and then the gas.
  • Conversely, to light an 02/gas torch, turn on the gas and add 02 until you attain the flame type and size that you want.  With the Smith Little Torch’s smaller tips, you’ll need to add O2 VERY, VERY SLOWLY, or the O2 blows out the flame.  Also, once the torch is lit, adding too much oxygen will blow out the torch.  Annoying, yet understandable.
  • When using a gas/O2 system, you will have two sets of regulators.  Oxygen regulators will have smooth inlet fittings and usually have green somewhere on them.  Gas regulators will be red, and the fittings will be grooved.
  • Your oxygen tank should be fully opened.
  • Your propane tank should be fully opened.
  • Your acetylene tank should be?   SET TO NO MORE THAN 15 PSI for acetylene!  Correct! (That was a test!).
Little Torch Disposable Regulator
Little Torch Gas Disposable Tank Regulator

The Smith Little Torch Preset Oxygen Regulator is green with a smooth inlet fitting (for portable gas cylinders).  The Smith Stage 1 Propane Regulator has a groove in that thingy that I think is called a nut.

Do not use any of Miller Smith’s “Heating Tips” (rosebud/multi-orifice) with a disposable oxygen canister.  See their catalog.

If you are using a Smith Little Torch with either Propane/O2 or Acetylene/O2, use this chart as a guide for setting tank pressures. Both oxygen and gas are set to the same pressures.

Flashback arrestors are recommended at the handle of your torch, but you won’t be able to attach them to the Smith Little Torch handle as there are no connectors.  So, you need to attach them to the regulator.  The disposable propane tanks don’t actually have regulators, though.

 Starting up your acetylene/air system

  • To start up, check that the torch tip is shut down and that the regulator control is loose and not engaged.
  • Check that the hose is in good repair.
  • Open up the tank with the key or knob.
  • You will see the right gauge register the level of your gas with a two-stage regulator.
  • Slowly (especially with acetylene) turn the T-bar or knob until the left-sided regulator begins to register pressure.  With acetylene (as stated 100 times so far), you should stop when it reaches ten psi – up until 15 psi, BUT NEVER ANY HIGHER!

Setting up your propane/air system

  • This setup is slightly different than with the acetylene.
  • If you are using propane with air, some say you don’t even need a regulator. (Discussion on Ganoksin).  Just use the gas as it comes from the tank.  I use a regulator, though.
  • After doing your safety checks, Ensure that the torch is shut off, that the regulators are loosened (if you have any), and the hose is checked.  Now you can open the tank.  Open up the gas tank all the way – unlike the acetylene, which is only opened up a few inches or about a 1/4 of a turn.
  • Turn the T-Bar or knob clockwise (if you have a regulator). You’ll be able to adjust the pressure later if your flame isn’t how you want it.  If it’s too high, lower the pressure by turning counter-clockwise on your regulator’s T-bar or knob.  If you need more heat, increase the pressure.  Your torch’s manual might have information on ideal settings for propane/air mixes.  Follow the recommended pressure levels in your torch’s instruction manual.

The Smith Little Torch can be used with disposable tanks.  The torches are made to work with Mapp (propylene), propane, and O2 disposable tanks.  You will find that you will use more oxygen tanks than gas, so buy extra. The ratio is nine oxygen tanks to one gas tank for propane with a #5 tip!  (See Smith’s PDF:  “Disposable propane cylinders have 7.50 cfh of gas. Disposable oxygen cylinders have 1.05 cfh of gas. This means that a No. 5 tip (12-1401-05) at 2.58 cfh propane and 3.1 cfh oxygen consumption would use up an oxygen cylinder in 20 minutes and a propane cylinder in three hours.” ).

Please see MF MetalArts’ video on the ratio of propane to O2 used with the Smith Little Torch and disposable canisters.  He found that the ratio can range from 15 to 30 canisters of oxygen to 1 canister of propane!  The variance is based on what type of flame you are using: oxidizing, carburizing, or neutral.  (In order:  an excess of oxygen, an excess of gas, an equal proportion of gas to oxygen).  An oxidizing flame will burn through oxygen faster.

Disposable and Refillable Propane Tanks

Please think twice about using small canisters of oxygen or propane.  See this video.

As of this writing, there is no recycling system in my area – Northern California – for the empty canisters. I called the manufacturer, and they didn’t know of any.  This is concerning as it all gets dumped into landfills or elsewhere.  So, consider this before purchasing a disposable system.  (See the update below).  You CANNOT refill disposable propane gas cylinders – unless they are specifically designed for refilling.

It is illegal and dangerous to refill standard one-pound disposable propane cylinders.

Traveling with refilled one-pound propane cylinders – those that are not designed for refilling – comes with a $500,000 fine plus five years of prison time for doing so.   Make sure that your cylinders are DOT legally and lawfully refillable and transportable. 

If you want to reduce waste, you can try Little Camper’s exchange program.   Little Camper has an exchange program where one-pound propane canisters are exchanged for new ones.  See their website for more information.  Reducing the number of cylinders in our landfills.

Flame King has a refillable 1/4-pound, 1/2-pound, and one-pound propane cylinder.

Flame King refillable propane tanks are the only 1/4 lb, 1/2 lb, and one lb tanks Certified by the DOT as legally and lawfully refillable and transportable. It is not safe or legal to refill and transport (regular – my note) disposable 1/4 pound, 1/2 pound, and one pound tanks.”  They sell empty tanks that you fill. 

Please visit my torch page to discover why you shouldn’t have propane cylinders larger than one pound in your studio and why you should only have two one-pound cylinders in your studio: one in use and one in storage.

***Please see this important safety information regarding the dangers of storing propane in your home and the illegal and dangerous practice of refilling camping propane tanks (aka 1# or DOT 39).

Other Gasses

Mapp Gas and Propylene Gas

I thought I’d throw this in! Who doesn’t like a little more information about gas?

Mapp gas is no longer being produced.  Although you may still find it in stores.  The new gas, Mapp-Pro, is actually liquid petroleum gas (LPG) with a large amount of propane gas. Propylene can be found at gas suppliers in larger tanks.  I just spoke with Airgas, and the man I spoke with stated that you have to rent the tanks.  Airgas sells a kit to use with the rental tanks. You also need special tips for the torch. The salesman at Airgas said you could use propane hoses but they won’t last very long.  He recommended using the hoses designed for Mapp gas.  Mapp gas, when mixed with O2, can reach temperatures of 5300 °F (2925 °C).  For comparison, Acetylene and O2 can reach  5720 °F (3160 °C). But it’s only a 420°F difference.  This is plenty hot for silver soldering!

If you have a torch kit for disposable Mapp/Propane tanks, you can use that with the Mapp-Pro.

Mapp-Pro burns at 3,730 degrees F, while propane burns at 3,600 degrees F.

Here’s a quote from Praxair on Propylene gas:

“When compared with acetylene, propylene offers greater safety as it can be utilized up to full tank pressure. It is well suited to being used at cold temperatures as it has a greater vapor pressure when compared with propane.”

Victor Technologies has an entire page on this subject.

I just finished a page on working with my new Oxygen Concentrator.  You should stop by!

Emergency responses involving compressed gases

NOTE:  The information is general information and should not be used as specific information for a particular gas.  In all cases of fire or explosion, call emergency services first.

Never use a tank that has received a severe shock or has been exposed to heat or fire.  Contact your gas supplier and let them know what happened.  They can advise you. When in doubt call emergency services.

This from, “Instructions for first response actions to be taken in event of a fire (excluding acetylene cylinders) • Warn personnel. • If present when the fire or heat events starts AND it is safe to do so, close any open cylinder valves and move nearby cylinders away before the fire spreads. • Evacuate the area. • Raise the alarm, call the emergency services and the gas supplier. • If possible, identify if any of the cylinders involved are of composite or aluminium alloy construction or have a pressure relief device (PRD). In this situation do not allow anyone to return to the area, and await arrival of the emergency services. • Keep other people out of the area. If safe and practical, barricade the area and place warning notices. • Only if a trained on-site emergency team is equipped and available should they immediately start the cooling of affected cylinders in accordance with written emergency procedures. Possible emergency team actions could include deluging cylinders with water from a safe location, for example from behind heavy machinery or a solid wall. Care shall be taken not to knock cylinders over when cooling. • Make a note (record) of the time that the fire or heating started, and if possible, the content, number and location of gas cylinders directly involved. • Give this information and all the information outlined in this SI to the emergency services on arrival.”

Compressed Gas Safety from Airgas.

Compressed Gas Safety University of California, Riverside.

Related Videos

Required Reading (IMHO)

Air Products:  SafetyGram – 13.  Acetylene. This is a very precise document and goes into more detail and with more technical information than my page presents.

Bibliography and For Further Research

  1. (n.a.) History:  “Acetylene Dissolved in Acetone”. Retrieved:  January 30, 2015. Website:
  2. (n.a.) “History: Gustaf Dalén”. Retrieved:  January 20, 2015.  Website:
  3. Air Products.  (Rev. February 1994) “Safety Gram-13, Acetylene (Pub. No. 310-721)“. Retrieved: January 29, 2015.
  4. Almqvist, Ebbe . (2003) “History of Industrial Gasses” Vol. XVIII. Springer Science & Business Media. Paris, France (?). Retrieved:  January 30, 2015.
  5. Benes, James of Welding Design and Fabrication.  (March 19, 2007) “A heads-up on hose and regulator safety“.  Retrieved:  October 2014-December 2014.
  6. Bensaude-Vincent, Bernadette for Encyclopedia Britannia. (October 29, 2013). “Pierre-Eugène-Marcellin Berthelot“. Retrieved: January 30, 2015.
  7. Bhatia, A., Fundamentals of Gas Cutting and Welding. Retrieved: 3/21/18.
  8. Compressed Gas Association (CGA) “Pamphlet G-1 2009”. Via: Web.  Retrieved: December 2, 2015.
  9. Erickson, Lexi.  (2007). “Set Up Your Torch”.   Retrieved:  December 2014.  Retrieved: October through December 2014. Ganoksin via Lapidary Journal Jewelry Artists Magazine:
  10. ESAB. (No Author, no date) Handbook – Oxygen and Acetylene.  Retrieved:  March 21, 2018.
  11. Heiserman, David L. Editor, Sweet Haven Publishing Services. (Revised: December 03, 2014).“Fundamentals of Professional Welding“.  Retrieved: January 29, 2015.
  12. Nobel Lectures, Physics 1901-1921. “Gustav Dalén – Biographical“.  (1967).  Elsevier Publishing Company, Amsterdam. Retrieved:  October 2014.
  13. Nobel Lectures, Söderbaum, H.G., Professor. (December 10, 1912). “Award Ceremony Speech“. Retrieved:  October – December 2014.
  14.  Today in Science History. (1999). “Edmund Davy“. Retrieved: January 30, 2015.
  15. Victor “Training Content by Category“. Retrieved: January 29, 2015. Victor
  16. For a WOW moment, check out: Even a small cylinder of acetylene can do a LOT OF DAMAGE…, Mike Schlags, My Firefighter Nation. Retrieved:  9/16/15. Web. 12/17/2009.
  17. Division of Mineral Mining, Virginia: Oxygen and Acetylene Use and Safety – a really good resource with lots of pictures!
  18. Tractor Supply Company. How to Select and Setup a Oxy-Acetylene Welding Rig. Retrieved: 9/16/15. Tractor Supply Company: Web.  Date published: unknown.
  19. United States Department of Labor.  Osha: Oxygen-fuel gas welding and cutting. Retrieved:  9/16/15. Occupational Safety & Health Administration – OSHA:  Web. Date published:  unknown.
  20. Rio Grande.  Rio Grande:  How To Safely Set Up An Oxygen/Propane Torch. Retrieved: 9/16/15. Rio Grande: Web video. Uploaded: 3/30/11.
  21. Weldcor: Encyclopaedia of Terms: OXYACETYLENE WELDING (OAW).  Retrieved: 9/17/15. Web. 2013.
  22. Karen Christians Clever Werx. Soldering Fundamentals. Retrieved: 9/17/15. Web. Date published: Unknown.
  23. Matheson: Guide to Regulators. Retrieved: 9/17/15. Matheson Gas:  Web. Date Published: 2014.
  24. California State University: Fullerton.  Environmental Health and Safety: Gas Regulators. Retrieved: 9/17/15. California State University: Fullerton: Web.  Date published: unknown.
  25. The Compressed Gas Association (CGA).  You can purchase publication TB-3 on Oxy-Fuel Hose Line Flashback Arrestors (or become a member and they are free) and SB-16: Use of High Flow Oxy-Fuel Gas Heating Torch Apparatus. They have many, many articles, bulletins, videos, libraries and safety alerts.
  26.  **Fundamentals of Professional Welding. David L. Heiserman, Editor. Sweethaven Publishing. Free-Ed Net: Retrieved: 9/17/15. Web. 6/6/15.
  27. OSH: Answers Fact Sheets. Compressed Gases – How Do I Work Safely with. The Canadian Center for Occupational Health and Safety. Retrieved: 9/17/15. Web. July 8, 2008.
  28. Silversmith and Handi-Heet torch manuals. Smith Equipment.  Retrieved: January 29, 2015. Web. July 2013.
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