Atmospheric Hazards
The most common hazard seen in confined spaces is that of atmospheric hazards. These affect air quality and present immediate hazards to health or life. Acceptable atmospheric conditions must be verified before entry, and must be monitored continuously while the space is occupied. The oxygen concentration, the presence of toxic gases, and flammable material are the three conditions that must be monitored.
Oxygen concentration is considered safe if it is between 19.5% and 23.5% of the total atmosphere. To protect against toxic gases, contaminants have permissible exposure limits (PELs), which are set by OSHA. Work also cannot continue if the concentration of a material reaches or exceeds 10% of its lower explosive limit.
Even if a tank or similar vessel initially is tested and found to contain breathable air, a hazard can develop during operations inside the tank if residues inside the tank can release toxic gas or vapor when disturbed or if accidentally ignited. Steel water tanks may have dangerously low oxygen concentration when the interior rusts.
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Famous quotes containing the word atmospheric:
“Nor has science sufficient humanity, so long as the naturalist overlooks the wonderful congruity which subsists between man and the world; of which he is lord, not because he is the most subtile inhabitant, but because he is its head and heart, and finds something of himself in every great and small thing, in every mountain stratum, in every new law of color, fact of astronomy, or atmospheric influence which observation or analysis lay open.”
—Ralph Waldo Emerson (1803–1882)