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150 Physical Health Hazards in Construction
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Confined Spaces

Confined spaces include manholes, sewers, vaults, tanks, and boilers in new construction or in repair and maintenance work. Exposure to chemicals or lack of oxygen in confined spaces can be deadly. Airborne chemicals can quickly reach dangerous levels in confined spaces that are not ventilated. Typical hazardous atmospheres within confined spaces include:

Airborne chemicals in confined spaces can reach dangerous levels in areas that are not ventilated.
  • lack of oxygen,
  • carbon monoxide,
  • hydrogen sulfide,
  • welding fumes, and
  • solvent vapors.

Oxygen deficiency is especially dangerous as it is typically not noticed until it's too late: the person entering a confined space may instantly collapse.

For more information on confined spaces in general industry, see course 713 Confined Space Program and course 816 Confined Space Safety in Construction.

Knowledge Check Choose the best answer for the question.

1-10. Why is oxygen deficiency so dangerous in confined spaces?