Flammable and oxidising gases

LPG

LPG is a mixture composed primarily of propane (C3H8) and, in smaller parts, butane (C4H10) and ethane (C2H6). The gas is colourless, and has a characteristic smell due to the addition of odourants. LPG is a heavy gas and can therefore move downwards and accumulate in low lying areas in the event of leakage.

LPG is stored under pressure as a liquid in gas cylinders. Common cylinder types are the smaller blue type known as “camping cylinders” (190, 340, 1200 and 2000 g LPG) and the larger silver-grey steel cylinders with the designation P plus a number indicating the weight of the LPG in (kg). The larger cylinder types are used when the LPG is supplied through a central system.

LPG cylinders must be handled with care and protected from abnormally high temperatures. The cylinders must always remain upright during handling and storage. The valve on the cylinder must be kept closed during storage. Labels and other markings must not be removed.

LPG is considered extremely flammable, and escaping gas requires only a very small amount of ignition energy to ignite. A gas-air mixture can result in a gas cloud explosion. Because the gas is heavier than air, it may accumulate at low points. This must be taken into account particularly when protecting against ignition sources. Because the gas is stored under pressure (7 bar at normal room temperature) in the cylinders, only equipment designed for this pressure may be connected to the cylinder outlet. Abnormal heating of LPG cylinders causes the pressure in the cylinder to increase. All types of LPG cylinder are equipped with a pressure relief valve as a safety device. The safety valve’s function and the safety of the gas outlet depend on the cylinder always remaining upright. If cylinders are lying on their side, there is a risk of the gas being released in liquid form, which presents major risks.

The gas has a strong cooling effect, and escaping gas as well as uninsulated equipment can cause frostbite.

Acetylene

Acetylene, sometimes referred to as welding gas, is a product name for ethyne, C2H2, which is a colourless gas with a faint garlic-like odour. The gas is stored under pressure (20 bar) in gas cylinders, dissolved in solvents (acetone or DMF). The cylinders are reddish brown all over.

Acetylene is considered extremely flammable, and escaping gas requires only a very small amount of ignition energy to ignite. A gas-air mixture can result in a gas cloud explosion. The gas is unstable and begins to decompose at temperatures above 300 °C. Decomposition can be triggered by external heating of the cylinder, e.g. by a fire or spot heating from a welding flame. Decomposition can also be triggered by a flashback. There is no pressure relief valve on acetylene cylinders. Decomposition results in a pressure increase and violent explosion of the cylinder. If heated strongly, the cylinder can explode within 5 minutes.

If any flashback or heating of acetylene cylinders to temperatures above 300 °C resulting in the start of acetylene decomposition is suspected, the premises must be evacuated and the emergency services called.

Explosive compounds may be formed if the gas comes into contact with copper, silver, mercury or brass containing more than 70% copper. Because the gas is stored under high pressure in the cylinders, only equipment designed for this pressure is to be connected to the cylinder outlet. During welding, flashback arrestors for acetylene must be used (also recommended for oxygen). Non-return valves must be fitted to burner handles for both acetylene and oxygen.

In the event of uncontrolled release of acetylene, the room must be evacuated and ventilated. If possible, turn off the flow of gas and, as far as possible, prevent the gas from igniting by eliminating any ignition sources. Always check the gas concentration before resuming activity at the premises. If the escaping gas ignites, the fire must be extinguished by shutting off the gas supply. If the burning gas is extinguished without stopping the gas flow, there is a risk of the gas reigniting and exploding.

Acetylene causes asphyxiation if inhaled, by displacing oxygen in the atmosphere. Anyone who has inhaled the gas and has breathing difficulties must be taken out into the fresh air. Artificial respiration should be given if the person has stopped breathing.

Gas cylinders must be handled with care and protected from abnormally high temperatures. The gas equipment must be checked regularly in respect of its function and escaping gas. When the cylinders are stored, the cylinder valve must be closed and the sealing plug tightened and secured to prevent them falling over and being damaged. Labels and other markings must not be removed.

Hydrogen

Hydrogen (H2) is a colourless, odourless gas. The gas is stored under high pressure in gas cylinders. Common cylinder types are 5, 10, 20 and 50 litre cylinders. The cylinders are black, with a red top.

Hydrogen is considered extremely flammable, and escaping gas requires only a very small amount of ignition energy to ignite. A gas-air mixture can result in a gas cloud explosion. Because the gas is lighter than air, it initially accumulates at ceiling level before later diffusing around the room. This must be taken into account particularly when protecting against ignition sources. The gas has a strong tendency to escape, which must be taken into account when reviewing the gas systems. The gas is stored under high pressure (200 bar) in the cylinders, and only equipment designed for this pressure is to be connected to the cylinder outlet. Abnormal heating of hydrogen cylinders causes the pressure inside the cylinder to increase, which can cause it to explode. There is no pressure relief valve on hydrogen cylinders.

In the event of uncontrolled release of hydrogen, the room must be evacuated and ventilated. If possible, turn off the flow of gas and, as far as possible, prevent the gas from igniting by eliminating any ignition sources. Always check the gas concentration before resuming activity at the premises. If the escaping gas ignites, the fire must be extinguished by shutting off the gas supply. If the burning gas is extinguished without stopping the gas flow, there is a risk of the gas reigniting and exploding.

Hydrogen causes asphyxiation if inhaled, by displacing oxygen in the atmosphere. Anyone who has inhaled the gas and has breathing difficulties must be taken out into the fresh air. Artificial respiration should be given if the person has stopped breathing.

Hydrogen cylinders must be handled with care and protected from abnormally high temperatures. The gas equipment must be checked regularly in respect of its function and escaping gas. When the cylinders are stored, the cylinder valve must be closed and the sealing plug tightened and secured to prevent them falling over and being damaged. Labels and other markings must not be removed.

Carbon monoxide

Carbon monoxide (CO) is a colourless, odourless gas. The gas is stored under high pressure in gas cylinders. The cylinders are black, with a red top.

Carbon monoxide is considered extremely flammable, and escaping gas requires only a very small amount of ignition energy to ignite. This gas mixes easily with air. Because the gas is stored under high pressure (200 bar) in the cylinders, only equipment designed for this pressure is to be connected to the cylinder outlet. Abnormal heating of the cylinders causes the pressure inside the cylinder to increase, which can cause it to explode. There is no pressure relief valve on the cylinders. In the event of uncontrolled release of carbon monoxide, the room must be evacuated and ventilated. If possible, turn off the flow of gas and, as far as possible, prevent the gas from igniting by eliminating any ignition sources. If the escaping gas ignites, the fire must be extinguished by shutting off the gas supply. Use a water spray (not a jet) or dry powder to extinguish the fire. 

Carbon monoxide causes asphyxiation if inhaled, by preventing red blood cells from carrying oxygen. Anyone who has inhaled the gas and has breathing difficulties must be taken out into the fresh air. Artificial respiration should be given if the person has stopped breathing.

Carbon monoxide cylinders must be handled with care and protected from abnormally high temperatures. The gas equipment must be checked regularly in respect of its function and escaping gas. When the cylinders are stored, the cylinder valve must be closed and the sealing plug tightened and secured to prevent them falling over and being damaged. Labels and other markings must not be removed.

Oxygen

Oxygen (O2), is not a flammable gas and is therefore not covered by the requirements for flammable products. However, the gas is oxidising and supports combustion. The gas is stored under pressure (200 bar). The cylinders are black, with a white top.

The gas is oxidising and facilitates ignition, as well as accelerating the development of fire, making it potentially explosive. In the event of an oxygen escape, the oxygen concentration must never be permitted to exceed 24% in the room.

Spot extraction should be used and good ventilation ensured. The gas equipment must be kept free of oil and grease and other particles to prevent spontaneous combustion. Only sealants and lubricants approved for use with this gas may be used. Because the gas is stored under high pressure in the cylinders, only equipment designed for this pressure is to be connected to the cylinder outlet. Valves must be opened carefully to avoid subjecting the gas equipment to pressure surges and powerful gas escape. Abnormal heating of the cylinders causes the pressure inside the cylinders to increase, which can cause them to explode. There is no pressure relief valve on oxygen cylinders.

In the event of uncontrolled release of oxygen, the room must be evacuated and ventilated. Clothing must also be aired. Fire in oxygen-enriched clothing cannot be extinguished by smothering it, but must be cooled and extinguished with water. If possible, turn off the gas flow.

The gas cylinders must be handled with care and protected from abnormally high temperatures. When the cylinders are stored, the safety valve must be closed and the valve guard must be applied, and the cylinders must be secured to prevent them falling over and being damaged. Labels and other markings must not be removed. The cylinders are to be stored separately from ignition sources in well ventilated areas at temperatures under 50 °C.