What is the minimum oxygen level required for entry into a confined space without supplied air respiratory protection?
Correct Answer
B) 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: 18.5%
18.5% oxygen is below the OSHA minimum threshold and would be considered oxygen-deficient atmosphere requiring supplied air respiratory protection
Option C: 20.5%
20.5% oxygen, while safe, is not the minimum threshold - OSHA allows entry at the lower 19.5% level
Option D: 21.0%
21.0% oxygen represents normal atmospheric conditions but is not the minimum required threshold for confined space entry
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
More Project Mgmt Questions
What is the minimum R-value required for wall insulation in Florida Climate Zone 2?
A subcontractor brings a new chemical product to your jobsite. Under the Globally Harmonized System (GHS), what information must be immediately available to workers?
A construction site has a trench that is 8 feet deep in Type B soil. What is the maximum allowable slope ratio for the trench walls without protective systems?
A detail drawing shows a scale of 3/4" = 1'-0". If a dimension measures 2.25 inches on the drawing, what is the actual dimension?
What is the maximum recommended spacing between drywall screws when attaching to wood studs?
People Also Study
Business & Financial Management
120 questions · 70% to pass
Contract Administration
60 questions · 70% to pass