Which type of respiratory protection is preferable for the repair/investigation personnel in a hydrogen sulfide (H2S) environment?

Correct Answer: Option C — Positive Self-Contained Breathing Apparatus (SCBA)

Positive pressure SCBA is the only acceptable respiratory protection for H2S environments. Unlike demand-type units, positive pressure ensures that any leakage in the face seal results in air flowing out rather than toxic gas flowing in, providing the highest level of protection for personnel entering hazardous or oxygen-deficient spaces.