Asphyxiants, occupational exposure

Carbon dioxide is toxic, can be an asphyxiant by virtue of oxygen displacement (described above), and can cause death due to paralysis of the respiratory centres (Hoather and Wright, 1989). The threshold limit value for CO2 is 0.5% and concentrations above 5% result in laboured breathing, headaches and visual disturbances. The long term occupational exposure limit (OEL) is 5,000 vpm and the short term occupational exposure limit (STEL) is 1.5% by volume. In most situations arising from landfill gas-associated problems, carbon dioxide toxicity will only occur when collection in an enclosed environment occurs. Under these conditions there would also be potential for explosion due to potentially high methane levels and gas control measures would be required to alleviate such a potentially dangerous situation. 

Immediately Dangerous To Life or Health (IDLH) This is a standard set by the National Institute of Occupational Safety and Health (NIOSH) which limits exposure to any toxic, corrosive, or asphyxiant substance that poses an immediate threat to life, or would cause irreversible or delayed adverse health effects, or world interfere with an individual s ability to escape from a dangerous atmosphere. 

High yields of smoke, toxins, and irritants are generated at temperatures around 600°C as the fire stage changes to under-ventilated flaming in an enclosure fire. A room occupant is exposed to a highly toxic effluent mixture capable of causing incapacitation and death from asphyxiation within a few minutes. They will also suffer from exposure to heat, with a possibility of burns. 

Acetylene is recognized internationally as a simple asphyxiant. The American Conference of Governmental Industrial Hygienists recommends that atmospheres containing acetylene have a minimum oxygen concentration of 18%. The National Institute of Occupational Safety and Health has a recommended exposure limit for acetylene of 2500 ppm as a ceiling. 

Selenium dioxide is formed when selenium is heated in air. Direct exposure to selenium dioxide is, therefore, primarily an occupational hazard and not likely to be a risk at hazardous waste sites. Selenium dioxide forms selenious acid on contact with water, including perspiration, and can cause severe irritation. Acute inhalation of large quantities of selenium dioxide powder can produce pulmonary edema as a result of the local irritant effect on alveoli (Glover 1970). Bronchial spasms, symptoms of asphyxiation, and persistent bronchitis have been noted in workers briefly exposed to high concentrations of selenium dioxide (Wilson 1962). Kinnigkeit (1962) reported that selenium dioxide concentrations of 0.007-0.05 mg selenium/m3 in a selenium rectifier plant produced slight tracheobronchitis in 9 of 62 exposed workers. 

The TLV represents the concentration under which it is believed that nearly all workers may be repeatedly exposed day after day without adverse effect, that is for 8 hours/ day, 40 hours/week. Apart from carbon dioxide (threshold limit value 5000 ppm) and simple asphyxiants such as nitrogen, the highest threshold limit value (least toxic) is 1000 ppm. A threshold limit value of 1000 ppm has been assigned for some fluorocarbons, and comparative data suggest similar values are reasonable for the other fluorocarbons discussed in this section. In many cases, the threshold limit values as established by the ACGIH have been adopted by the U.S. Occupational Safety and Health Administration (OSHA) as workplace exposure limits. See 29 CFR 1910.1000. [13]... 

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