Compressed Gases

US Department of Transportation Definitions

Flammable Gases

• Having a pressure exceeding 40 psia at 70 F, or

• Having a pressure exceeding 104 psia at 130 F or,

• Any flammable liquid material with a vapor pressure >40 psia at 100 F.

Flammable Compressed Gases

• Having Lower Explosive Limit > 13% by volume, or

• Having a flammability range >12%, is easily ignited, and the flame and heat propagation rate resemble explosion

Rules for Handling Compressed Gases

• Always use a hand truck for transport and chain cylinder to hand truck

• Do not transport in closed vehicles

• Cylinders should be chained in place or otherwise secured at all times

• Leave valve cap on cylinder until secured and ready for use

• Do not drop cylinders, or otherwise permit them to strike each other

• Ground all cylinders containing flammable gases

• Use the proper regulator for the particular gases

• All valves should be closed when not in actual use

• Use only in an upright position

• Carefully open all valves and adjust gas flow rates

• Always consider cylinders to be full and handle accordingly

• Discontinue using a high-pressure cylinder when the pressure approaches 30 psia, clearly mark "EMPTY" and remove for return to vendor

• Oily (i.e., not specially cleaned) fittings should never be used with oxygen

• Oxygen under pressure may rapidly oxidize oil or grease resulting in an explosion. Specially cleaned equipment must be used.

• Acetylene under pressure can decompose with explosive force and can explode with extreme violence if ignited. Copper or brass (with more than 65% copper) can form explosive compounds with acetylene.

• Glass equipment should not be pressurized. A general rule is no pressure > 10 inches of water without special protective equipment.

• Never mix gases in a cylinder. Explosion, contamination, corrosion, and other hazards can result.

• Cylinders containing large amounts of a flammable gas (hydrogen, acetylene, ethylene) should be stored outside in a protected area and piped into the working area

• Store in a fire-proof, well-ventilated area

• Storage area temperature should be regulated, so as not to exceed 100° F

• Store gases supporting combustion (O₂, Cl₂, etc.) at least 20 feet from fuel gases, if there is no protective wall, preferably in another gas area

ValuJet 592 Everglades crash¹

• Oxygen canisters were being transported in the cargo hold of the DC-9 for use on other planes - an FAA violation.  These oxygen canisters, which are in lined compartments above each seat in an airplane, create a very strong exothermic (heat-producing) reaction when the two components in the canisters are mixed.   (Flight attendants instruct you on commercial planes to pull down on the oxygen mask to mix the two chemicals in the canisters that produces oxygen and heat).

• The oxygen canisters were improperly labeled as empty - an FAA violation

• The oxygen canisters were lacking $1.00 safety caps - an FAA violation

• Spare aircraft tires were being transported in the cargo hold - an FAA violation

Shortly after takeoff, the oxygen canisters began reacting and generating a hot, oxygen-enriched atmosphere in the cargo hold.  The heat was sufficient to ignite the nearby tires. The oxygen-fed tire fire got sufficiently hot that it melted the steering cables running through the cargo hold causing the pilots to lose control of the aircraft.

¹Information gathered from the news media

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