What are the Hazards Involved in Entering and Working in Confined Spaces?

Hazardous Atmospheres

The atmosphere in a confined space may be extremely hazardous because of the lack of natural air movement. This characteristic of confined spaces can result in

  1. Oxygen-deficient atmospheres,
  2. Flammable atmospheres, and/or
  3. Toxic atmospheres.

An oxygen-deficient atmosphere has less than 19.5% available oxygen (O2). Any atmosphere with less than 19.5% oxygen should not be entered!

The oxygen level in a confined space can decrease because of work being done, such as welding, cutting, or brazing; or, it can be decreased by certain chemical reactions (rusting, paint drying) or through bacterial action (fermentation).

The oxygen level is also decreased if oxygen is displaced by another gas, such as carbon dioxide or nitrogen, resulting from inerting or fire suppression. Total displacement of oxygen by another gas, such as carbon dioxide, will result in unconsciousness, followed by death.

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