OSHA Confined Spaces Quiz — 29 CFR 1926.1200-1213 Practice Questions (Subpart AA) — Page 2 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. (Page 2 of 4)
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Q11/ 40
A worker is tasked with entering a newly installed 36-inch diameter storm drain pipe to inspect the interior joints. The pipe runs 200 feet between manholes. The worker must crawl inside with a flashlight. Is this a confined space under 1926 Subpart AA?
✅ Correct Answer: B
1926.1202: a confined space is defined as a space that: (1) is large enough and so configured that an employee can bodily enter and perform assigned work; (2) has limited or restricted means for entry or exit; (3) is not designed for continuous employee occupancy. A 36-inch pipe running 200 feet between manholes meets all three. Whether it's a permit-required confined space depends on whether it contains or has the potential to contain: hazardous atmosphere, engulfment hazard, configuration that could trap/asphyxiate, or any other recognized serious safety hazard.
Q12/ 40
A crew works inside a 10-foot deep concrete electrical vault (manhole) pulling cable. The vault has a single 24-inch manhole opening at the top. Workers descend via a ladder. No air monitoring has been done. They've been working for 2 hours. One worker complains of dizziness. What's the most likely cause?
✅ Correct Answer: B
1926.1203(e)(1): before entry, the space must be tested for oxygen, combustible gases/vapors, and toxic air contaminants. 1926.1203(e)(2): testing must be done in the order: oxygen content, then combustible gases, then toxic substances. Underground electrical vaults are notorious for atmospheric hazards: (1) rust (oxidation) consumes O₂ — levels can drop below 19.5% (IDLH), (2) CO from vehicles/equipment settles in low areas, (3) H₂S from bacterial action in stagnant water. Dizziness is a classic symptom of hypoxia. The entry supervisor's failure to test before and monitor during entry is a life-threatening violation. Workers should evacuate immediately and not re-enter until the atmosphere is tested and found safe.
Q13/ 40
The confined space entry permit for a sewer lift station lists the entry supervisor as 'John.' John leaves the site for a doctor's appointment 2 hours into the planned 6-hour entry. Workers remain in the confined space. The permit is still posted. Is the entry still valid?
✅ Correct Answer: B
1926.1204(e)(1)(v): the entry supervisor must be present and available to perform their duties during the entry. 1926.1204(e)(1)(vi): the entry supervisor shall terminate the entry and cancel the permit when conditions warrant. The entry supervisor must: (1) be present, (2) know the hazards, (3) verify permit conditions remain consistent with safe entry, (4) be available to terminate entry and coordinate rescue. If John leaves and no other qualified entry supervisor is designated and on-site, the permit is effectively void — workers must exit. The permit is not a 'set and forget' document.
Q14/ 40
Two workers enter a permit-required confined space (a tank being welded inside, with continuous forced-air ventilation). After 30 minutes, the attendant notices one worker looking drowsy. The gas monitor reads: O₂ 20.6%, LEL 4%, CO 38 ppm. The attendant radios the workers: 'you OK?' The drowsy worker gives a thumbs up but isn't speaking clearly. What must the attendant do?
✅ Correct Answer: B
1926.1208(d): the attendant shall order an evacuation when: (1) a hazardous condition is detected, (2) behavioral effects of hazard exposure are observed in entrants, (3) a situation outside the space could endanger entrants, or (4) the attendant can no longer effectively perform duties. Behavioral symptoms (drowsiness, slurred speech) ARE hazard indicators, regardless of meter readings. The 4-gas meter (O₂/LEL/CO/H₂S) does NOT detect: solvent vapors (VOCs like toluene, xylene), welding fumes, isocyanates, or many other toxic chemicals. The attendant must NOT enter — 1926.1208(c): attendants shall not perform duties that interfere with the primary duty to monitor and protect. Entering would create a second victim. Call trained rescue, ventilate more, and monitor from outside.
Q15/ 40
A contractor is entering a newly constructed utility tunnel (400 feet long, 4 feet diameter) to install pipe supports. The tunnel has one entrance. Air monitoring shows O₂ 20.9%, LEL 0%, CO 0 ppm, H₂S 0 ppm initially. Workers enter. After 1 hour, the far end (200 feet from the entrance) has O₂ at 19.3%. Workers at the far end don't have personal monitors — only the entrance has a monitor. Are these conditions acceptable?
✅ Correct Answer: B
1926.1203(e)(2)(vi): the atmosphere must be continuously monitored. 1926.1203(d)(1): testing must be done in a manner to accurately sample the atmosphere. For a 400-foot lineal space with one entrance, the far end 200 feet from the entrance acts as a dead-end where heavier gases can accumulate and oxygen can be consumed by human respiration and oxidation. The O₂ gradient (20.9% at entrance, 19.3% at far end) shows the ventilation is not reaching the work area. 1926.1203(e)(1)(iii): oxygen below 19.5% = IDLH. Workers must exit until adequate ventilation reaches the far end and O₂ is verified ≥19.5% at the work position. Personal monitors on each worker are industry best practice.
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Q16/ 40
A contractor decides a tank entry does NOT need a permit because 'we do this all the time and it's always been fine.' The tank previously contained diesel fuel, was drained and steam-cleaned 2 days ago. No air monitoring is done. Two workers enter to repair a valve. What is required before such a decision?
✅ Correct Answer: B
1926.1203(a): before entry, the employer must determine if the space is a permit-required confined space. 1926.1203(d)(1): air monitoring must be done before entry. A diesel tank, even steam-cleaned, can have: (1) residual vapors from sludge/pockets not reached by cleaning, (2) oxygen deficiency if rust consumes O₂ faster than the manhole admits air, (3) H₂S or CO from residual fuel decomposition. The contractor's anecdotal 'always been fine' does not substitute for testing. 1926.1203(g) allows reclassifying a permit space to non-permit IF: no actual or potential atmospheric hazards exist AND all other hazards are eliminated — but this requires testing to prove, not assumption. A diesel tank is a permit-required confined space until air monitoring PROVES it is safe.
Q17/ 40
An entry supervisor records pre-entry atmospheric test results on the permit, signs it, and workers enter. The permit does NOT include: the rescue service contact information, the communication method between attendant and entrants, or the list of equipment (harnesses, retrieval line, ventilation). Is the permit compliant?
✅ Correct Answer: B
1926.1204(c): the entry permit must contain (at minimum) all 12 listed items. Missing rescue service info means if an emergency occurs, no one knows who to call or whether a rescue team is on standby. Missing communication procedures means the attendant may not know how to contact entrants (radio channel, rope pulls, voice). Missing equipment list means critical safety gear may not be present (and indeed, retrieval equipment is missing). An incomplete permit is non-compliant — the permit is not just a formality, it's a safety checklist that verifies all safeguards are in place before entry.
Q18/ 40
A worker enters a manhole that has been closed for 6 months. No air monitoring. Within 30 seconds, the worker collapses. A co-worker at the surface sees this and immediately climbs down the ladder to rescue them. The co-worker also collapses. What just happened?
✅ Correct Answer: B
1926.1209(a): the employer must develop and implement procedures for summoning rescue and emergency services. 1926.1209(c): retrieval systems must be used unless they would increase the overall risk. Over 60% of confined space fatalities are would-be rescuers — the phenomenon is so well-documented it has its own name. A manhole closed for 6 months likely has: (1) O₂ consumed by rust/organic decomposition (well below 19.5%), (2) accumulated H₂S from stagnant water (paralyzes olfactory nerve at high concentrations — you can't smell it when it's deadly), (3) CO or methane. The correct rescue procedure: NEVER enter without supplied-air respirator and backup team. Use non-entry rescue (retrieval line and winch to pull the worker out) if possible. Call 911. This scenario repeats itself dozens of times each year.
Q19/ 40
The atmosphere in a 12-foot deep sewer manhole is tested before entry: O₂ 20.8%, LEL 0%, CO 5 ppm, H₂S 0 ppm. The competent person classifies it as a non-permit space and allows entry without a permit. Workers enter and begin cleaning. 3 hours later, a worker notices a rotten egg smell. What must happen?
✅ Correct Answer: B
1926.1203(e)(2)(vi): the atmosphere shall be continuously monitored during entry. 1926.1203(e)(2)(iii): if a hazardous atmosphere is detected after entry, employees must evacuate immediately and the space re-evaluated. H₂S (rotten egg smell) was not present initially but the cleaning activity disturbed sludge, releasing trapped H₂S. This is why continuous monitoring is essential — the initial test is a snapshot, not a guarantee of safety for the duration. H₂S causes olfactory paralysis at concentrations above 100 ppm: the smell disappears, making workers think the hazard is gone, while the concentration rises to fatal levels (>1,000 ppm causes immediate collapse and death). Evacuation is mandatory.
Q20/ 40
A construction worker enters a crawlspace under a house to repair plumbing. The crawlspace is 30 inches high, accessed through a 22-inch × 30-inch hatch. The worker crawls 40 feet from the hatch to the repair location. Is this a confined space?
✅ Correct Answer: B
1926.1202 definitions apply to all construction, including residential. A 30-inch high crawlspace with a small access hatch 40 feet from the work location is a confined space: (1) a person CAN bodily enter (crawl), (2) exit is limited — in an emergency, crawling 40 feet in 30 inches of height to a small hatch is extremely restrictive, (3) it's not designed for occupancy. Crawlspaces frequently have: sewer gas from damaged pipes, radon in certain regions, mold/fungi (respiratory hazard), pest waste (hantavirus), and low oxygen from insulation off-gassing. Atmospheric testing and ventilation should be considered before entry.