Flammable and oxidising gases
Flammable gases are those gases that can ignite in air at a temperature of 20 °C and an atmospheric pressure of normal air pressure, 101.3 kPa. A flammable gas that is in liquid form at a temperature lower than 20 °C and a pressure higher than atmospheric pressure or a combination of both, is a condensed gas. Such gas is still to be considered a flammable gas.
LPG
LPG is a composition of mostly propane (C3H8) and smaller parts of butane (C4H10) and ethane (C2H6). The gas is colorless and has a characteristic odor due to added odorants. LPG is a heavy gas and can penetrate low-lying spaces if released. The gas is stored under pressure in a condensed (liquid) state in gas cylinders. The larger cylinder types are used in central gas pipeline systems. LPG is considered extremely flammable and leaking gas requires only very little ignition energy to ignite. A gas/air mixture can cause a gas cloud explosion.
Routine LPG
- Gas cylinders are handled carefully and protected against abnormal heating. Abnormal heating of the gas cylinders causes an increase in pressure in the cylinder.
- The cylinders should always be handled and stored upright. When storing, the cylinders should have the valve closed. Labels or other markings must not be removed.
Pressure relief in the form of a safety valve is available on all types of gas cylinders. The function of the safety valve and a safe gas outlet is based on the cylinder always being in an upright position; a lying cylinder can cause a direct outlet of the liquid phase, which poses a great risk. The gas has a strong cooling effect and escaping gas and uninsulated equipment can cause frostbite.
Acetylene
Acetylene, sometimes referred to as welding gas, is the product name for ethyne, C2H2, which is a colorless gas with a faint garlic-like odor. The gas is stored under pressure (20 bar) in gas cylinders dissolved in a solvent (acetone or DMF). Acetylene is considered extremely flammable and leaking gas requires only very little ignition energy to ignite. A gas/air mixture can cause a gas cloud explosion. The gas is unstable and begins to decompose when heated above 300 °C. The decomposition can be started by external heating of the cylinder, for example in a fire or spot heating from a welding flame. Decomposition can also be started by a continuous backfire.
Pressure relief in the form of a safety valve is not available on acetylene gas cylinders. The decomposition results in a pressure increase and violent rupture of the cylinder. In the event of severe heating, the vessel can burst within 5 minutes. Risk remains for up to 24 hours after heating has ended.
If there is suspicion of backfire or heating of the acetylene cylinder above 300 °C and acetylene decomposition has begun, the premises must be evacuated and the fire department must be called.
Explosive compounds can be formed if the gas comes into contact with copper, silver, mercury or brass with more than 70% copper. Since the gas is stored under high pressure in the cylinders, only equipment intended for this pressure may be connected to the cylinder outlet.
Welding
When welding, backfire protection for acetylene must be available (also recommended for oxygen). Non-return valves must be available on the torch handle for both acetylene and oxygen.
In the event of an uncontrolled release
In the event of an uncontrolled release of acetylene, the premises must be evacuated and ventilated. If possible, turn off the gas flow and avoid ignition of the gas as much as possible by eliminating any ignition sources. Always check the gas level before resuming operations on the premises. If the leaking gas is burning, extinguishing should be done by turning off the gas supply. If the burning gas is extinguished without stopping the gas flow, there is a risk of re-ignition and explosion.
Inhalation
Acetylene has a suffocating effect when inhaled by displacing oxygen from the air. If the gas is inhaled and breathing difficulties occur, the person should be taken to fresh air. Artificial respiration should be given if breathing has stopped.
Routine acetylene
Gas cylinders should be handled with care and protected against abnormal heating. Gas equipment should be checked regularly for function and leakage. When stored, the cylinders should have the valve closed and the tight cap tightened, and be secured so that they cannot fall over and be damaged. Labels or other markings may not be removed.
Hydrogen
Hydrogen, H2, is a colorless and odorless gas. The gas is stored under high pressure in gas cylinders. Hydrogen is considered extremely flammable and a leaking gas requires only very little ignition energy to ignite. A gas/air mixture (oxyhydrogen) can cause a gas cloud explosion. Because the gas is lighter than air, the gas initially accumulates at the ceiling before it diffuses into the room at a later stage. This should be taken into account in particular when protecting against ignition sources. The gas has a high tendency to leak, which is taken into account when inspecting the gas system. The gas is stored under high pressure (200 bar) in the cylinders and only equipment intended for this pressure may be connected to the cylinder outlet. Abnormal heating of the hydrogen cylinders causes a pressure increase in the cylinder, which can lead to a vessel bursting. Pressure relief in the form of a safety valve is not available on the hydrogen cylinders.
In case of uncontrolled release
In case of uncontrolled release of hydrogen gas, the premises must be evacuated and ventilated. If possible, turn off the gas flow and avoid ignition of the gas as much as possible by eliminating any ignition sources. Always check the gas content before resuming operations in the premises. If the leaking gas is burning, extinguishing should be done by turning off the gas supply. If the burning gas is extinguished without stopping the gas flow, there is a risk of re-ignition and explosion.
In case of inhalation
Hydrogen gas has a suffocating effect when inhaled by displacing the oxygen in the air. If the gas is inhaled and breathing difficulties occur, the person must be taken out into fresh air. Artificial respiration must be given if breathing has stopped.
Routine hydrogen gas
Hydrogen cylinders must be handled with care and protected against abnormal heating. Gas equipment must be checked regularly for function and leaks. When storing, the bottles must have the valve closed and the stopper tightened, and must be secured so that they cannot fall over and be damaged. Labels or other markings must not be removed.
Carbon monoxide
Carbon monoxide, CO, is a colorless and odorless gas. The gas is stored under high pressure in gas cylinders. Carbon monoxide is considered extremely flammable and a leaking gas requires only very little ignition energy to ignite. The gas mixes easily with air. Because the gas is stored under high pressure (200 bar) in the cylinders, only equipment intended for this pressure may be connected to the cylinder outlet. Abnormal heating of the cylinder causes a pressure increase in the cylinder, which can cause the vessel to burst. Pressure relief in the form of a safety valve is not available on the cylinders.
In the event of an uncontrolled release
In the event of an uncontrolled release of carbon monoxide, the premises must be evacuated and ventilated. If possible, turn off the gas flow and avoid ignition of the gas as much as possible by eliminating any ignition sources. If the leaking gas burns, extinguishing should be done by turning off the gas supply, using water spray (not jet) or dry powder for extinguishing.
Inhalation
Carbon monoxide is suffocating when inhaled by preventing red blood cells from absorbing oxygen. If the gas is inhaled and breathing difficulties occur, the person should be taken to fresh air. Provide respiratory support if breathing has stopped.
Routine carbon monoxide
Carbon monoxide cylinders should be handled with care and protected from abnormal heating. Gas equipment should be checked regularly for function and leaks. When stored, the cylinders should have the valve closed and the tight cap tightened, and be secured so that they cannot fall over and be damaged. Labels or other markings may not be removed.