CMC Regulatory Compliance and Standards 2 — Questions and Answers
Question 1: Under OSHA 29 CFR 1915.12, what is the minimum acceptable oxygen concentration for a worker to enter a confined space without supplied-air respiratory protection?
- 16.0%
- 18.0%
- 19.5% (Correct answer)
- 20.5%
Correct answer: 19.5%
OSHA 29 CFR 1915.12 defines an oxygen-deficient atmosphere as one with less than 19.5% oxygen by volume, below which supplied-air or SCBA is required.
Question 2: NFPA 306 classifies a vessel space as 'Gas Free' for hot work when flammable vapor concentration is at or below what percentage of the Lower Explosive Limit (LEL)?
- 0%
- 5%
- 10% (Correct answer)
- 25%
Correct answer: 10%
NFPA 306 requires flammable vapor to be at or below 10% LEL before a space is certified 'Gas Free' for hot work operations.
Question 3: Which federal regulation specifically governs hot work operations aboard vessels in shipyards and requires a Marine Chemist certificate for certain operations?
- 29 CFR 1910.146
- 29 CFR 1915.14
- 46 CFR Part 35 (Correct answer)
- 49 CFR Part 172
Correct answer: 46 CFR Part 35
46 CFR Part 35 (Hot Work) governs hot work on vessels and specifies when a Marine Chemist or Coast Guard authorized person must certify the space.
Question 4: Under 29 CFR 1915.7, who is authorized to certify a vessel space as safe for hot work when a Marine Chemist is not available?
- A licensed ship officer
- A Coast Guard Marine Inspector or a shipyard competent person (Correct answer)
- Any OSHA-trained safety officer
- A certified industrial hygienist
Correct answer: A Coast Guard Marine Inspector or a shipyard competent person
29 CFR 1915.7 allows a U.S. Coast Guard Marine Inspector or, in their absence, a shipyard competent person to certify spaces when a Marine Chemist is unavailable.
Question 5: When testing a confined space atmosphere before entry, OSHA 29 CFR 1915.12 requires testing to be performed in what sequence?
- Flammable, then toxic, then oxygen
- Toxic, then oxygen, then flammable
- Oxygen, then flammable, then toxic (Correct answer)
- Flammable, then oxygen, then toxic
Correct answer: Oxygen, then flammable, then toxic
OSHA requires oxygen concentration to be tested first, then flammable gases/vapors, then toxic substances, because sensor accuracy is affected by oxygen levels.
Question 6: Under NFPA 306, how frequently must a Marine Chemist re-test and re-certify a vessel space during continuous hot work operations if conditions remain unchanged?
- Every 30 minutes
- Every 2 hours
- Before each new work shift
- Only if conditions change or work is interrupted more than 30 minutes (Correct answer)
Correct answer: Only if conditions change or work is interrupted more than 30 minutes
NFPA 306 requires re-certification if conditions change or if work is interrupted for more than 30 minutes, not on a fixed time interval under stable conditions.
Question 7: An oxygen concentration of 23.6% in a vessel compartment creates what type of hazard classification under OSHA 29 CFR 1915?
- Oxygen-deficient atmosphere
- Immediately Dangerous to Life or Health (IDLH)
- Oxygen-enriched atmosphere (Correct answer)
- Non-permit required confined space
Correct answer: Oxygen-enriched atmosphere
Any oxygen concentration above 23.5% is classified as an oxygen-enriched atmosphere, which dramatically increases fire and explosion risk.
CMC Regulatory Compliance and Standards 2
Under OSHA 29 CFR 1915.12, what is the minimum acceptable oxygen concentration for a worker to enter a confined space without supplied-air respiratory protection?