An atmosphere that is oxygen-deficient requires what action before entry?

• A. No precautions
• B. Wait for ambient conditions to change
• C. Additional precautions, use of PPE, and possibly SCBA, due to insufficient oxygen
• D. Ignore it if there is a buddy

Answer: (C)

An oxygen-deficient atmosphere presents an immediate life‑threatening hazard, so you must address it before anyone enters. The proper approach is to verify the environment with calibrated detectors to confirm oxygen levels and check for other hazardous contaminants, ventilate to improve conditions if possible, and, if oxygen remains insufficient, enter only with enhanced protection—appropriate PPE and an independent breathing source such as an SCBA or supplied‑air system, plus a trained attendant and a formal entry permit. Relying on no precautions, waiting for ambient conditions to change, or entering with a buddy without protective equipment all fail to manage the atmospheric danger effectively.