What is the minimum oxygen level required for entry into a confined space without supplied air respiratory protection?
Correct Answer
C) 19.5%
OSHA requires a minimum oxygen level of 19.5% for safe entry into confined spaces. Levels below this require supplied air respiratory protection or other atmospheric controls.
Why This Is the Correct Answer
OSHA's confined space entry standard (29 CFR 1910.146) specifically requires a minimum oxygen concentration of 19.5% for safe entry without supplied air respiratory protection. This threshold ensures workers have adequate oxygen to breathe safely while accounting for normal variations in atmospheric conditions. Below this level, workers face serious risks of oxygen deficiency, which can cause impaired judgment, unconsciousness, or death. This is a critical safety standard that general contractors must enforce on job sites involving confined spaces.
Why the Other Options Are Wrong
Option A: 20.5%
18.5% oxygen is below the OSHA minimum threshold and would be considered oxygen-deficient atmosphere requiring supplied air respiratory protection
Option D: 21.0%
20.5% oxygen, while safe, is not the minimum threshold - OSHA allows entry at the lower 19.5% level
Memory Technique
Think '19.5 to stay alive' - this helps remember that 19.5% oxygen is the minimum level needed for safe confined space entry
Reference Hint
OSHA 29 CFR 1910.146 - Permit-Required Confined Spaces standard, or safety/health chapter in contractor reference materials
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