Ê×Ò³| Â鶹´«Ã½Ó³» Compressed Gases
Compressed gases present a variety of potential physical and chemical hazards in their storage, delivery, and use. Gases may be classified as toxic, pyrophoric, flammable, irritant, corrosive, inert, and oxidizing. Large releases of inert gases may displace air and cause asphyxiation although this is most apt to occur in confined spaces. Some compressed gases may have more than one potential hazard, for example, chlorine gas is corrosive, toxic, and oxidizing. Physical hazards may involve a sudden release of pressure which results in major damage to the facility or serious personal injury. Personal injury may also be caused by the improper handling of gas cylinders.
Gas Cabinets
Gas cabinets are recommended for storage of flammable gases and are required for highly toxic and pyrophoric compressed gases. These cabinets are ventilated so that laboratory occupants are protected from any release of a harmful gas from the gas cylinder, regulator, or manifold. They also minimize the hazards from external or internal fires. Safety features of gas cabinets can include sprinkler heads and heat and/or toxic gas sensors within the cabinet.
Types Of Compressed Gases
- Inert: a non-flammable, non-reactive gas that is not considered to be hazardous unless the gas is uncontrollably released. These gases still have a potential for asphyxiation (oxygen depletion). These gases include nitrogen or helium in compressed or liquid form.
- Flammable: a gas which may ignite at concentrations between the upper and lower explosive limits (acetylene).
- Oxidizing: may promote rapid combustion of flammable gases or materials (nitrous oxide).
- Corrosive: reactive gas which may degrade materials and cause damage to bodily tissues upon contact (hydrogen chloride).
- Toxic: a poisonous gas which may cause acute reactions or death (hydrogen sulfide).
Safety Precautions
- Select the least hazardous gas that will work for your application.
- Purchase only the necessary quantities.
- Select gases with returnable containers.
- Wear appropriate foot protection when moving cylinders and eye protection at all times when moving or manipulating compressed gas cylinders.
- All compressed gas cylinders must be clearly labeled as to their contents.
- All compressed gas cylinders must be secured (clamp, belt, or chain) at all times.
- When not in use, all compressed gas cylinders must have a valve cap on.
- At the time of receipt of hazardous/flammable gases and whenever regulators are changed, check for leaks with a soap bubble solution (commercially available preparations are available).
- Check a catalog for the proper CGA regulator before connecting any regulator to a cylinder, and slowly open the valve in case of a leak or damaged regulator.
- Move cylinders only with the aid of a cylinder transport cart with a restraining strap or chain. Never roll a cylinder to move it or carry a cylinder by the valve.
- Run only rigid tubing that is compatible with the gas used, from the cylinder to the instrument.
- Never store oxidizing gases with flammable gases.
- Keep cylinders away from open flames and sources of heat.
Chemicals of Concern
Be aware that there are certain chemicals of concern (including compressed gases) that when ordered in the following concentrations require a security questionnaire from the manufacturer during the ordering process.
| Chemical | Concentration |
|---|---|
| Ammonia | (pure) |
| Arsine | ≥ 0.4% |
| Boron Trifluoride | ≥ 16.12% |
| Chlorine | ≥ 5.8% |
| Ethylene Oxide | ≥ 87% |
| Hydrogen Bromide | ≥ 57.2% |
| Hydrogen Chloride | ≥ 62.4% |
| Hydrogen Fluoride | ≥ 26% |
| Hydrogen Sulfide | ≥ 14.24% |
| Phosphine | ≥ 0.4% |
| Sulfur Dioxide | ≥ 50.4% |