Hazardous properties of gases

Please note that before attempting to move or use laboratory gases you should be fully aware of the hazards associated with the gas. An MSDS sheet can be supplied from Biology Stores.

Hazardous property	Examples
Corrosive	ammonia, chlorine, hydrogen chloride, hydrogen fluoride
Flammable	acetylene, butane, hydrogen, methane, propane
Oxidizers	oxygen, chlorine
Toxic	carbon monoxide, ethylene oxide
Cryogenic	nitrogen, carbon dioxide, oxygen

Note: all cylinders of compressed gases should be handled as high energy sources and therefore as potential explosives.

Acetylene

Acetylene is the most thermodynamically unstable common gas, is highly flammable, has a very wide explosive range (from 2% to 80% in air), and under pressure and certain conditions can decompose with explosive force. To allow safe handling of acetylene in cylinders, suppliers use a porous packing material saturated with a solvent in which the acetylene dissolves. The combination of porous filling and solvent markedly enhances the stability of acetylene.

Argon, Carbon Dioxide, Helium and Nitrogen

These gases are all inert, colourless, odourless, and tasteless but can cause asphyxiation and death in confined, poorly ventilated areas. In addition these gases can cause severe frostbite to the eyes or skin. Some carbon dioxide cylinders contain a tube and are intended for liquid withdrawal. These cylinders are specially marked; be sure you are using equipment appropriate to the application. Air will condense on exposed helium liquid or cold-gas surfaces, such as vaporizers and piping. Nitrogen, having a lower boiling point than oxygen, will evaporate first, leaving an oxygen-enriched condensation on the surface. To prevent possible ignition of grease, oil, or other combustible materials, care must be taken that equipment is free of these materials.

Hydrogen

Hydrogen is a flammable gas. A mixture of hydrogen and oxygen or air in a confined area will explode if ignited by a spark, flame or other similar source. Escaping hydrogen cannot be detected by sight, smell or taste and, because of its lightness, it has a tendency to accumulate in the upper portions of confined areas. Use of a hydrogen generator should always be considered first where possible. If a generator is not appropriate, the cylinder must be fitted with a gas detector linked to an automatic shut-off valve. If not, this must be fully justified in the risk assessments for the work activity involving the use of hydrogen.

Oxygen

Oxygen supports and can greatly accelerate combustion; keep combustibles away from oxygen and eliminate ignition sources. Oxygen is colourless, odourless, and tasteless and as a liquid or cold gas may cause severe frostbite to the eyes or skin. Many materials, especially some non-metallic gaskets and seals, constitute a combustion hazard when in oxygen service, although they may be acceptable for use with other gases. Before attaching a regulator to an oxygen cylinder, be certain that the regulator and inlet filter are free of oil, grease, or other contaminants, and crack the cylinder valve momentarily to blow out any dust or dirt that might have accumulated in the cylinder valve outlet.