CHST Confined Space Entry and Rescue 5 — Questions and Answers
Question 1: Which atmospheric condition in a confined space is MOST immediately life-threatening and requires immediate evacuation without any other assessment?
- Oxygen concentration of 19.4%
- Carbon monoxide reading of 25 ppm
- LEL reading at 12% of lower explosive limit (Correct answer)
- Hydrogen sulfide reading of 1 ppm
Correct answer: LEL reading at 12% of lower explosive limit
An LEL reading of 12% indicates a significant flammable atmosphere; evacuation is required when LEL reaches or exceeds 10% of the lower explosive limit.
Question 2: A construction worker is performing hot work inside a confined space with documented atmospheric testing. The work is paused for a 30-minute lunch break. Upon return, the worker should:
- Resume work since the permit is still valid
- Re-test the atmosphere before re-entering the space (Correct answer)
- Have the entry supervisor verbally confirm it is still safe
- Wait 15 additional minutes as a precaution then re-enter
Correct answer: Re-test the atmosphere before re-entering the space
Atmospheric conditions can change rapidly during breaks, especially with hot work; retesting before re-entry is required to ensure continued safety.
Question 3: The primary purpose of continuous forced-air ventilation in a permit-required confined space is to:
- Maintain temperature comfort for workers
- Replace and control hazardous atmospheres during occupancy (Correct answer)
- Reduce the need for gas monitoring equipment
- Eliminate the need for respiratory protection
Correct answer: Replace and control hazardous atmospheres during occupancy
Forced-air ventilation continuously dilutes and removes hazardous gases to maintain a safe atmosphere while workers occupy the space.
Question 4: Which of the following rescue methods is always preferred over all others for confined space rescue per OSHA regulations?
- Emergency services (fire department) rescue
- Non-entry retrieval using mechanical means (Correct answer)
- Entry rescue by a trained employer rescue team
- Mutual aid rescue by neighboring contractor teams
Correct answer: Non-entry retrieval using mechanical means
OSHA requires that non-entry retrieval be used whenever it is feasible, because it protects rescuers from entering the hazardous space.
Question 5: A confined space attendant who must temporarily leave their post due to an emergency should:
- Instruct an entrant to monitor from inside the space
- Have another authorized attendant replace them before leaving (Correct answer)
- Lock the entry point and leave immediately
- Notify OSHA before departing the area
Correct answer: Have another authorized attendant replace them before leaving
An attendant may not abandon their post unless relieved by another qualified attendant, as continuous external monitoring is essential to entrant safety.
Question 6: Which type of confined space hazard is classified as an 'engulfment' hazard under OSHA's confined space standard?
- Exposure to electrical wiring in a vault
- Being surrounded and captured by liquid or finely divided solid material (Correct answer)
- Entanglement with rotating machinery inside a tank
- Asphyxiation from oxygen-deficient atmosphere
Correct answer: Being surrounded and captured by liquid or finely divided solid material
Engulfment specifically refers to the surrounding and effective capture of a person by liquid or finely divided solid material such as grain, sand, or slurry.
Question 7: Under OSHA 29 CFR 1926.1204, which of the following is a required duty of the entry supervisor for a permit-required confined space?
- Remain inside the confined space for the duration of the work
- Verify that all conditions specified by the permit have been met before authorizing entry (Correct answer)
- Personally test all atmospheric conditions using a calibrated monitor
- Submit a copy of the entry permit to OSHA before entry begins
Correct answer: Verify that all conditions specified by the permit have been met before authorizing entry
The entry supervisor must verify that all permit conditions are met and sign the permit to authorize entry before any worker enters the space.
CHST Confined Space Entry and Rescue 5
Which atmospheric condition in a confined space is MOST immediately life-threatening and requires immediate evacuation without any other assessment?