What is the minimum oxygen level required for entry into a confined space without supplied-air respiratory equipment?
Correct Answer
B) 19.5%
OSHA requires a minimum oxygen concentration of 19.5% for safe entry into confined spaces. Below this level, supplied-air respiratory equipment is mandatory to prevent asphyxiation.
Why This Is the Correct Answer
OSHA 29 CFR 1926.95 and 1910.146 establish 19.5% as the minimum acceptable oxygen concentration for confined space entry without supplied-air respiratory equipment. This standard is based on physiological research showing that oxygen levels below 19.5% can cause impaired judgment, increased heart rate, and other dangerous symptoms. The 19.5% threshold provides a safety margin above the 16% level where serious physiological effects begin to occur. This is a critical safety requirement that contractors must follow to protect workers from asphyxiation hazards.
Why the Other Options Are Wrong
Option A: 20.5%
18.5% oxygen concentration is below OSHA's minimum safety threshold and would create dangerous conditions for workers. At this level, workers would experience oxygen deficiency symptoms including impaired judgment, increased heart rate, and potential loss of consciousness, making entry unsafe without supplied-air equipment.
Option D: 21.0%
21.0% represents normal atmospheric oxygen concentration at sea level, but OSHA recognizes that slight oxygen depletion can occur in confined spaces. The regulation allows for entry at 19.5% minimum, acknowledging that perfect atmospheric conditions aren't always achievable in confined work environments.
Memory Technique
Remember '19.5 to stay alive' - this rhyme helps recall that 19.5% is the minimum oxygen level needed to safely enter confined spaces without supplied air
Reference Hint
OSHA 29 CFR 1926.95 (Personal Protective Equipment) and 29 CFR 1910.146 (Permit-Required Confined Spaces) - look for oxygen concentration requirements in confined space entry procedures
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