An oxygen-deficient atmosphere has less than 19.5% oxygen by volume, a deadly confined space hazard that requires supplied-air respiratory protection.
An oxygen-deficient atmosphere is air that contains less than 19.5 percent oxygen by volume, as defined by OSHA. Normal air contains about 20.9 percent oxygen. Oxygen levels can drop when gases such as nitrogen, argon, carbon dioxide or methane displace air, or when oxygen is consumed by rusting, combustion, bacteria or chemical reactions. Because people can't sense low oxygen, an oxygen-deficient atmosphere can cause impaired judgment, collapse and death within minutes, often with no warning.
A tank purged with nitrogen after cleaning reads 15 percent oxygen at the manway. The entry supervisor halts entry, has the tank ventilated with fresh air until continuous readings stay above 19.5 percent, and requires continuous monitoring during the job.
No. Low oxygen has no smell, and the body doesn't give a reliable warning. Workers may lose judgment and consciousness before realizing anything is wrong.
Yes. Oxygen-enriched atmospheres, above 23.5 percent in confined spaces, greatly increase fire risk because materials ignite more easily and burn faster.
An atmosphere-supplying respirator, such as a self-contained breathing apparatus or a supplied-air respirator with an auxiliary escape supply.
Part of SafetyIQ's EHS glossary: plain-English definitions of workplace health and safety terms.
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