CMC Confined Space Entry Requirements 2 — Questions and Answers
Question 1: Under OSHA 29 CFR 1915, what is the minimum oxygen concentration considered acceptable for entry into a confined space aboard a vessel?
- 16.5% by volume
- 19.5% by volume (Correct answer)
- 21.0% by volume
- 23.5% by volume
Correct answer: 19.5% by volume
OSHA 1915 requires a minimum of 19.5% oxygen by volume for safe entry into a confined space.
Question 2: Which document authorizes workers to enter a permit-required confined space on a vessel?
- Hot work permit
- Entry permit signed by the marine chemist or competent person (Correct answer)
- Safety data sheet
- Vessel safety plan
Correct answer: Entry permit signed by the marine chemist or competent person
An entry permit, signed by the authorized entrant or marine chemist, formally documents that safe conditions have been verified.
Question 3: What action must be taken before testing the atmosphere of a tank that previously contained flammable cargo?
- Ventilate for at least 30 minutes
- Purge with inert gas
- Ensure the space is gas-free of cargo vapors before entering (Correct answer)
- Apply fire-retardant coating
Correct answer: Ensure the space is gas-free of cargo vapors before entering
The space must be rendered gas-free of flammable cargo vapors before atmospheric testing and entry.
Question 4: What is the maximum permissible concentration of carbon monoxide (CO) for safe entry into a vessel's confined space per OSHA 1915?
- 25 ppm
- 35 ppm
- 50 ppm (Correct answer)
- 100 ppm
Correct answer: 50 ppm
OSHA 1915 sets 50 ppm as the ceiling for CO in confined spaces aboard vessels.
Question 5: When a marine chemist labels a space 'Safe for Workers,' what does this designation specifically mean?
- The space is safe for hot work operations
- The atmosphere is safe for entry without respiratory protection (Correct answer)
- The space is inert and worker entry is prohibited
- Fire suppression systems have been deactivated
Correct answer: The atmosphere is safe for entry without respiratory protection
'Safe for Workers' means the atmosphere meets oxygen, flammable vapor, and toxic gas requirements for entry without supplied air.
Question 6: Which type of ventilation is preferred for confined spaces with heavy vapors that settle near the bottom?
- Top-exhaust only ventilation
- Natural draft ventilation
- Forced air supply at the top
- Bottom-exhaust mechanical ventilation (Correct answer)
Correct answer: Bottom-exhaust mechanical ventilation
Bottom-exhaust mechanical ventilation removes heavy vapors that accumulate at the lowest points of the space.
Question 7: If continuous atmospheric monitoring detects a flammable vapor reading of 12% LEL during entry operations, what must occur?
- Increase ventilation and continue work
- Immediately evacuate all personnel from the space (Correct answer)
- Switch to supplied-air respirators and continue
- Notify the shipowner and resume after 15 minutes
Correct answer: Immediately evacuate all personnel from the space
A reading above 10% LEL requires immediate evacuation until the atmosphere is re-evaluated and controlled.
CMC Confined Space Entry Requirements 2
Under OSHA 29 CFR 1915, what is the minimum oxygen concentration considered acceptable for entry into a confined space aboard a vessel?