During a confined space entry, the atmospheric testing shows 18% oxygen, 50 ppm hydrogen sulfide, and no flammable gases. What action should be taken?
Correct Answer
D) Prohibit entry until atmosphere is corrected
Both the oxygen level (18%, below the 19.5% minimum) and hydrogen sulfide level (50 ppm, above the 10 ppm ceiling) create immediately dangerous conditions. Entry must be prohibited until the atmosphere is properly corrected.
Why This Is the Correct Answer
Option D is correct because the atmospheric conditions present two serious hazards that make entry immediately dangerous. The oxygen level at 18% is below the OSHA minimum requirement of 19.5%, creating a risk of asphyxiation. Additionally, the hydrogen sulfide concentration of 50 ppm significantly exceeds the OSHA ceiling limit of 10 ppm, which can cause immediate health effects including respiratory irritation and potential unconsciousness. Both conditions must be corrected before any entry is permitted.
Why the Other Options Are Wrong
Option A: Ventilate the space and retest before entry
Standard PPE is inadequate for these dangerous atmospheric conditions. The low oxygen level and high hydrogen sulfide concentration require complete atmospheric correction, not just protective equipment.
Option B: Enter with supplied air respiratory protection only
While ventilation and retesting are good practices, they are insufficient as immediate actions when dealing with both oxygen deficiency and toxic gas levels that exceed safe limits. Entry must be completely prohibited until conditions are safe.
Memory Technique
Use 'STOP at 19-10': If oxygen drops below 19.5% OR H2S exceeds 10 ppm, STOP all entry until corrected.
Reference Hint
OSHA 1926 Subpart AA - Confined Spaces in Construction, specifically 1926.1203 for atmospheric testing requirements and permissible exposure limits
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