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816 Confined Space Safety in Construction
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Hazardous Atmospheres

  • Oxygen deficiency: Oxygen-deficient atmospheres (oxygen concentration below 19.5 percent) affect heart rate, muscle coordination, and breathing. Unprotected workers cannot survive in an oxygen-deficient atmosphere.
Safe Yesterday, Deadly Today
  • Oxygen enrichment: Oxygen-enriched atmospheres (oxygen concentration above 23.5 percent), which can be caused by welding and from the improper use of oxygen for breathing air, increase the risk of fire or explosions.
  • Toxic dusts, mists, fumes, smoke, vapors, fibers, or gases: These can be released by manufacturing processes, stored materials, and work tasks. A hazardous atmosphere that poses a threat to life, would cause irreversible adverse health effects, or that would interfere with an individual's ability to escape from a confined space is called immediately dangerous to life or health (IDLH).

Some hazardous atmospheres (hydrogen fluoride gas and cadmium vapor, for example) may cause serious health effects that result 12 to 72 hours after exposure.

Knowledge Check Choose the best answer for the question.

1-5. What is a characteristic of a hazardous atmosphere?