Introduction
This topic covers toxic gases and vapours as chemical hazards in the workplace: where they come from, and their classification by health effect.
Gases
True gases exist as vapor at normal room temperature and pressure. Many can be stored as liquids under pressure; improper storage and use leads to contamination of workplace air.
Gases from use
- Chlorine: water treatment facilities
- N2O (nitrous oxide, laughing gas): anesthesia
- Ammonia: refrigeration plants
- O2: liquid O2 sources
- Hydrogen cyanide: grain fumigation
Gases that occur as by-products of industrial processes
- CO: incomplete fuel burning
- Nitrogen oxides, NO: diesel exhaust
- Ozone: electric arc welding machines
- H2S: sewers and waste water treatment facilities
Vapours
Vapours arise from evaporation of materials that are liquids at room temperature (solvents, adhesives, paints, chemical reactants, catalysts, sterilants). Solvents are the largest source of vapours: they dissolve material and readily vaporize into the atmosphere (acetone, chloroform, ethanol, CFCs, hexane, ethylene).
Occupational health aspects
Gases and vapours are classified into 3 groups for health and safety purposes.
- Irritant gases and vapours: cause inflammation of exposed tissues. Mild: mild irritation of eyes, nose and throat; severe: damage of lung (chlorine, nitrogen oxides, ...).
- Asphyxiants: simple asphyxiants have little direct physical effect, only displace O2 from air (CO2, N2O, helium, methane); chemical asphyxiants interfere with O2 transport in blood (CO, hydrogen cyanide) and are toxic in small concentration.
- Miscellaneous / other gases and vapours: many gases and nearly all vapours; acute effects on the CNS; chronic effects in many different organs.
- Helium: vocal changes
- N2O: analgesia
- O2 excess: pulmonary edema
- O2 deficit: brain disturbances, CNS effects
- Nitroglycerine: vasodilator, decreased BP
- Benzene: leukemia, damages bone marrow and suppresses immunity