OSHA Confined Spaces Quiz — 29 CFR 1926.1200-1213 Practice Questions (Subpart AA) — Page 1 of 4
Free OSHA 30-Hour Construction confined spaces practice test with 40 realistic scenarios. Permit-required spaces, atmospheric testing, ventilation, attendant duties, rescue, and entry permits with 29 CFR 1926 Subpart AA references.
0 / 10
Q1/ 40
A worker is tasked with entering a newly installed 36-inch diameter storm drain pipe to inspect the interior joints. The pipe extends 80 feet between manholes at a 2% slope. There is no mechanical ventilation inside. The space has limited entry/exit openings and is not designed for continuous occupancy. What must the employer do before entry?
✅ Correct Answer: B
1926.1202: a 'confined space' has three criteria: (1) is large enough for an employee to enter, (2) has limited or restricted means of entry/exit, (3) is not designed for continuous employee occupancy. This 36-inch pipe meets all three. 1926.1203(a): before entry, the employer must determine if it's a permit-required confined space. Storm drains can contain: oxygen deficiency (rust consumes O₂), hydrogen sulfide (decaying organic matter), methane (sewer gas), and carbon monoxide. Without air monitoring, entry is prohibited if hazards are unknown.
Q2/ 40
A crew is working inside a 10-foot deep concrete vault (electrical manhole) pulling cable. The vault has a single 24-inch manhole cover for access. A gas monitor at the opening reads: O₂ 20.0%, LEL 8% of methane, CO 25 ppm, H₂S 0 ppm. Workers have been inside for 4 hours with a blower providing fresh air. What is concerning about these readings?
✅ Correct Answer: B
1926.1203(e)(2)(i): the atmosphere must have at least 19.5% oxygen. At 20.0%, O₂ is technically above the minimum, BUT the downward trend from ambient (20.9%) indicates something is consuming oxygen — oxidation of cable materials, rust, or displacement by another gas (methane, from the LEL reading). 8% LEL for methane = approximately 0.4% methane by volume (methane LEL is ~5%). This is below the 10% LEL alarm threshold but MUST be investigated — the source could be a gas leak that will increase. Continuing work without identifying the cause is dangerous.
Q3/ 40
The confined space entry permit for a sewer lift station lists the entry supervisor as 'John.' John gets called to another emergency and hands his radio to another supervisor, 'Mike,' saying 'watch the crew for me.' Mike is not listed on the permit and hasn't reviewed the hazards. Is this acceptable under 1926.1204?
✅ Correct Answer: B
1926.1204(e): the entry supervisor must be identified on the permit. 1926.1204(f): the entry supervisor's duties include: knowing the hazards, verifying rescue services are available, verifying acceptable entry conditions, terminating entry when operations are complete OR when a condition not allowed by the permit arises. Mike, not having reviewed the hazards or rescue plan and not being named on the permit, cannot perform these duties. The crew must exit the space until a qualified entry supervisor is present. Handing a radio to an unqualified person is not 'delegation' under the standard.
Q4/ 40
Two workers enter a permit-required confined space (a tank being welded inside, with ventilation). The attendant is stationed outside the tank. The attendant needs to use the restroom. There is no other trained attendant on site. What does 1926.1208(c) require?
✅ Correct Answer: B
1926.1208(c): the attendant shall not leave the attendant's station while entrants are inside the space unless all entrants have exited and the space is closed, or a qualified relief attendant has taken over. This is absolute — there is no 'quick break' exception. The attendant's primary duty is monitoring entrants and summoning rescue — if the attendant is in the restroom when an entrant collapses, minutes matter for survival (4 minutes without oxygen = brain damage). The entrants must exit, even if the attendant is only leaving for a short time.
Q5/ 40
A contractor is entering a newly constructed utility tunnel (400 feet long, 4 feet diameter) to install cables. The tunnel has one access shaft at the midpoint. Workers will be up to 200 feet from the access point. What does OSHA 1926.1209 require for rescue in this configuration?
✅ Correct Answer: B
1926.1209(a): the employer must ensure rescue and emergency services are available. 1926.1209(c): non-entry rescue (using retrieval systems — harness, tripod, winch) must be used UNLESS the retrieval equipment would increase the overall risk of entry or would not contribute to rescue. For a worker 200 feet inside a 4-foot tunnel who collapses, a tripod and winch at the nearest access point may not work. The employer must evaluate: can the local fire department perform a horizontal rescue 200 feet into a 4-foot pipe? If not, a dedicated on-site rescue team with SCBA and extraction equipment is required. 'Call 911' is not a rescue plan.
Advertisement
Google AdSense — Responsive In-Article Ad
Q6/ 40
During a confined space entry into a degreaser pit, the gas monitor alarms for LEL (Lower Explosive Limit) at 15% of methane. The entry supervisor tells workers 'that's still below the 20% alarm, keep working.' What does 1926.1203(e)(2)(iii) require when LEL is detected?
✅ Correct Answer: B
1926.1203(e)(2)(iii): the atmosphere must have a concentration of flammable gas, vapor, or mist LESS THAN 10% of its lower explosive limit (LEL). At 15%, this atmosphere has FAILED the acceptance criterion. Workers must exit immediately. The alarm setpoint of 20% (a common industry setting) is a LAST CHANCE alarm, not the safe working limit. The OSHA limit is 10% LEL — half the alarm setpoint. Continuing to work at 15% LEL means any spark, static discharge, or hot work could ignite the accumulated gas.
Q7/ 40
A supervisor decides a tank entry does NOT need to be classified as a permit-required confined space because 'we have a blower running.' The tank has no other hazards identified, and air monitoring shows normal atmosphere. Under 1926.1203, can the employer reclassify a PRCS as a non-permit space?
✅ Correct Answer: B
1926.1203(g): an employer may reclassify a permit space as a non-permit confined space only if: (1) the space poses no actual or potential atmospheric hazards (not just controlled by ventilation), and (2) all hazards have been eliminated without entry into the space. The distinction between 'eliminated' and 'controlled' is critical. A blower CONTROLS (doesn't eliminate) an atmospheric hazard — if the blower fails, the hazard returns. Therefore, a blower-dependent atmosphere cannot be reclassified. The space must be entered as a PRCS with all attendant requirements.
Q8/ 40
An entry supervisor records the pre-entry atmospheric test results, signs the permit, and workers enter a tank. Four hours later, workers report feeling lightheaded. The entry supervisor re-tests and finds O₂ at 19.0% (below the 19.5% minimum). Workers are still inside. What must happen immediately?
✅ Correct Answer: B
1926.1204(e)(1)(vi): the entry supervisor shall terminate entry and cancel the permit when entry operations have been completed or a condition that is not allowed under the entry permit arises. 1926.1203(e)(2)(i): the atmosphere must contain at least 19.5% oxygen. At 19.0%, the acceptance criterion has been lost. The workers' lightheadedness is a symptom of hypoxia. The entry supervisor must: (1) order immediate evacuation, (2) cancel the permit, (3) re-evaluate the space — what changed? (4) implement corrective measures (more ventilation, identify O₂ consumer), (5) issue a new permit before re-entry. No 'quick fix' while workers remain inside.
Q9/ 40
A construction worker enters a manhole that has been closed for 6 months. No air monitoring is done because 'a manhole isn't a confined space if it's on a construction site.' The worker collapses within seconds from hydrogen sulfide (H₂S) exposure. A second worker sees this and rushes in to help — and also collapses. What fundamental confined space protocol failed?
✅ Correct Answer: B
This describes the most common confined space fatality pattern: initial victim collapses from an undetected atmospheric hazard → untrained rescuer impulsively enters to save them → both die. 1926.1203(d): before entry, the internal atmosphere shall be tested with a calibrated direct-reading instrument for oxygen, flammable gases, and potential toxic air contaminants. H₂S is a 'knockdown' gas at high concentrations — one breath at >1,000 ppm causes immediate collapse and respiratory paralysis. The second worker's death was preventable: 1926.1209 requires a rescue plan and rescue-trained personnel. Approximately 60% of confined space fatalities are would-be rescuers.
Q10/ 40
After a confined space entry is completed for the day, the permit is still active (space is left open, to be re-entered the next morning). The entry supervisor goes home without canceling the permit. Overnight, a maintenance worker sees the open manhole and enters to retrieve a dropped tool, without any testing or permit. Is the employer in compliance?
✅ Correct Answer: B
1926.1204(e)(1)(vii): the entry supervisor shall cancel the permit when entry operations are completed or a condition not allowed by the permit arises. The permit is valid only for the duration of the entry operation — not 24 hours. 1926.1204(e)(2): a new permit must be issued for each entry. The maintenance worker entered without a permit, without testing, and without an attendant — three separate violations. The employer's failure to cancel and secure the space created a situation where an untrained worker could enter a potentially hazardous atmosphere. Manhole covers should have been replaced or the opening barricaded and signed.