Industrial Hygiene – Air Contaminants II
Gases, vapors and chemical hazards
Gases are formless fluids that expand to occupy the space or enclosure in which they are confined. Examples are welding gases such as acetylene, nitrogen, helium, argon, and carbon monoxide generated from the operation of internal combustion engines or by its use as a reducing gas in a heat treating operation. Another example is hydrogen sulfide which is formed wherever there is decomposition of materials containing sulfur under reducing conditions.
Vapors are the volatile or gaseous form of substances that are normally in a solid or liquid state at room temperature and pressure. They are formed by evaporation from a liquid or solid and can be found where parts cleaning and painting takes place and where solvents are used.
When engineering, work practice or administrative controls are not adequate to protect employees from gases and vapors a face mask with a specific cartridge might be used. The specific mask and cartridge is dependent upon the characteristics of the gas or vapor such as vapor pressure, toxicity, concentration, and warning properties. If these characteristics are not known, then a supplied air system must be used.
Harmful chemical compounds in the form of solids, liquids, gases, mists, dusts, fumes, and vapors exert toxic effects by inhalation (breathing), absorption (through direct contact with the skin), or ingestion (eating or drinking). Airborne chemical hazards exist as concentrations of mists, vapors, gases, fumes, or solids. Some are toxic through inhalation and some of them irritate the skin on contact; some can be toxic by absorption through the skin or through ingestion, and some are corrosive to living tissue.
The degree of worker risk from exposure to any given substance depends on the nature and potency of the toxic effects and the magnitude and duration of exposure.
Information on the risk to workers from chemical hazards can be obtained from the Safety Data Sheet (SDS) that OSHA’S Hazard Communication Standard requires be supplied by the manufacturer or importer to the purchaser of all hazardous materials. The SDS is a summary of the important health, safety, and toxicological information on the chemical or the mixture’s ingredients. Other provisions of the Hazard Communication Standard require that all containers of hazardous substances in the workplace have appropriate warning and identification labels.