Confined Space Entry

Exam blueprint

Sourced from 29 CFR 1926 Subpart AA (Construction) + 29 CFR 1910.146 (General Industry) — Permit-Required Confined Spaces

• Definitions — confined space vs. permit-required12%
• Hazard identification + program requirements13%
• Atmospheric hazards + monitoring18%
• Entry permit + duties of roles15%
• Ventilation + isolation (LOTO/blinding)12%
• Non-entry vs. entry rescue13%
• Construction multi-employer coordination10%
• Training + recordkeeping7%

1. 01Definitions + the permit-required test

   ~60min

   OSHA defines a confined space narrowly. Not every tight space is a confined space, and not every confined space is permit-required — but the wrong call here puts workers in caskets.

   • Confined space — three-part definition

     A "confined space" under 1926.1202 / 1910.146(b) has THREE characteristics, ALL of which must be present: (1) is large enough and configured so a worker can BODILY ENTER and perform work; (2) has LIMITED OR RESTRICTED MEANS for entry or exit (manholes, roof hatches, narrow openings); AND (3) is NOT DESIGNED FOR CONTINUOUS OCCUPANCY. A storage tank with a manhole, a sewer, a crawl space, a pit, a vault, an HVAC duct, an underground utility vault — all confined spaces. A small office bathroom is not (it is designed for occupancy). The configuration test matters more than the size — a large but narrow-mouthed tank is still confined.

     Reference: 29 CFR 1926.1202

   • Permit-required confined space — the four hazards

     A confined space becomes PERMIT-REQUIRED if it has ONE OR MORE of: (1) HAZARDOUS ATMOSPHERE — actual or potential (oxygen deficiency/enrichment, flammable, toxic); (2) ENGULFMENT MATERIAL (loose grain, sand, sludge, water that could swallow a worker); (3) INTERNAL CONFIGURATION that could trap or asphyxiate (inwardly converging walls, sloping floors); OR (4) ANY OTHER RECOGNIZED SERIOUS HAZARD (mechanical, electrical, thermal, falling-object). Most construction confined spaces are permit-required by default until the competent person proves otherwise. Reclassification to "non-permit" is allowed under 1926.1203(g) but only after all hazards are eliminated, not just controlled.

     Reference: 29 CFR 1926.1203

   • Alternate procedures — the narrow path

     Section 1926.1203(e) allows ALTERNATE PROCEDURES (entry without a full written permit) ONLY when the only hazard is ATMOSPHERIC and continuous forced-air ventilation can keep the atmosphere safe — and you can document it with monitoring. The alternate-procedures path is heavily abused; many sites use it because the paperwork is shorter, when in fact the space has non-atmospheric hazards and full permit entry is required. When in doubt, use the full permit.

     Reference: 29 CFR 1926.1203(e)

   Practice questions (2)

   1. 1. A 4-foot-deep utility pit on a construction site has a hinged steel cover. Workers enter to repair valves. Confined space?

      • A.No — pits are excluded
      • B.No — under 6 feet deep is not confined
      • C.Yes — meets all three criteria (entry possible, restricted access, not designed for continuous occupancy)✓ correct
      • D.Only if it has an atmospheric hazard

      Depth is irrelevant. The three-part test is met: workers bodily enter, the hinged cover restricts entry/exit, and the pit is not designed for continuous occupancy. It is at minimum a confined space; whether it is permit-required depends on its hazards (atmospheric, engulfment, configuration, other).

   2. 2. Which condition does NOT, by itself, make a confined space permit-required?

      • A.Hazardous atmosphere (actual or potential)
      • B.Engulfment material
      • C.Internal configuration that could trap a worker
      • D.A coworker outside the space attending✓ correct

      An attendant outside the space is a CONTROL, not a hazard. The four conditions that make a space permit-required are: hazardous atmosphere, engulfment material, trapping configuration, and any other recognized serious hazard. Adding an attendant does not change classification.

2. 02Atmospheric hazards + monitoring

   ~90min

   Oxygen deficiency kills more confined-space workers than any other hazard. Master the % thresholds, the right testing order, and why a single grab-sample is malpractice.

   • Oxygen — 19.5% to 23.5% safe band

     Normal atmospheric oxygen is 20.9%. SAFE BAND for confined-space entry is 19.5% (lower) to 23.5% (upper). Below 19.5% is OXYGEN-DEFICIENT — at 16% workers begin to lose judgment, at 12% they collapse, at 6% they die in minutes. Above 23.5% is OXYGEN-ENRICHED — the atmosphere becomes a fire/explosion risk because materials that are non-flammable in normal air can ignite in 24%+ O2. Oxygen deficiency in tanks is most often caused by displacement (nitrogen purge, CO2 from decomposition) or consumption (rust, biological activity).

     Reference: 29 CFR 1926.1202 + 1926.1204(e)

   • LEL / Flammable + toxic limits

     FLAMMABLE atmosphere is one with combustible gas/vapor at 10% OR MORE of the LEL (Lower Explosive Limit) — well below the level at which it would actually burn, but the safety margin guards against pocketing of higher concentrations. TOXIC atmosphere is anything above the OSHA Permissible Exposure Limit (PEL) for that substance — for example, hydrogen sulfide PEL is 10 ppm time-weighted average, 20 ppm ceiling. Combustible dust at high concentration is also a flammable atmosphere. NEVER enter a space with > 10% LEL.

     Reference: 29 CFR 1926.1202

   • Test ORDER — oxygen, flammable, toxic

     Atmospheric testing MUST be done in this order: (1) OXYGEN first — most flammable-gas detectors require a normal O2 atmosphere to read accurately; (2) FLAMMABLE/COMBUSTIBLE second; (3) TOXIC third. Test BEFORE entry, then CONTINUOUSLY MONITOR while entry is in progress (or at frequent intervals if continuous monitoring is not feasible — but the standard prefers continuous). Test AT MULTIPLE DEPTHS — gases stratify. Hydrogen sulfide is heavier than air and pools at the bottom; methane is lighter and pockets at the top. A single mid-depth grab-sample misses both.

     Reference: 29 CFR 1926.1204(e)(1)(ii)

   • Hydrogen sulfide — the silent killer

     H2S is the leading cause of confined-space fatalities in sewers, manure pits, and oil-and-gas vessels. At low ppm it smells like rotten eggs; ABOVE ~100-150 ppm it PARALYZES THE OLFACTORY NERVE and you can no longer smell it — workers think the hazard cleared when in fact concentrations are climbing. At 700-1000 ppm a single breath causes "knockdown" — immediate loss of consciousness. NEVER trust your nose; trust the meter.

   Practice questions (3)

   1. 1. OSHA permit-required confined-space oxygen safe band?

      • A.18.0% to 22.0%
      • B.19.5% to 23.5%✓ correct
      • C.20.0% to 25.0%
      • D.15.0% to 30.0%

      19.5% (lower) to 23.5% (upper) per 1926.1202. Below 19.5% is oxygen-deficient and causes hypoxia; above 23.5% is oxygen-enriched and creates fire/explosion risk because normally non-flammable materials ignite. The other ranges are common distractors but not the OSHA values.

   2. 2. Correct order for atmospheric testing of a confined space?

      • A.Toxic, flammable, oxygen
      • B.Oxygen, flammable, toxic✓ correct
      • C.Flammable, oxygen, toxic
      • D.Order does not matter as long as all three are tested

      Oxygen first — most LEL meters use catalytic-bead sensors that need a normal O2 atmosphere to read accurately; in O2-deficient air the LEL meter reads artificially low. Flammable second to detect explosion risk before any spark source enters. Toxic third. Order matters because reading order affects accuracy.

   3. 3. A sewer worker reports the rotten-egg smell stopped — concludes the H2S has cleared. Correct interpretation?

      • A.Yes, the H2S has cleared
      • B.No — H2S above ~100-150 ppm paralyzes the olfactory nerve, so loss of smell may mean concentration is INCREASING✓ correct
      • C.It depends on the temperature
      • D.Smell is not relevant — meters only

      H2S olfactory paralysis is the classic killer mechanism. The smell disappears NOT because gas dissipated but because the nose stopped working. Meter data is the only valid measurement. The temperature distractor is irrelevant; "smell is not relevant" is true generally but option 2 specifically explains why this worker is wrong.

3. 03Entry permit + roles

   ~75min

   The four roles (entry supervisor, attendant, authorized entrant, rescue service) and what each is required to know, sign, and do.

   • What the permit must contain

     Per 1926.1206 the entry permit must include: (a) the space identified, (b) the purpose of entry, (c) the date and authorized duration, (d) authorized entrants by name (or means of identifying them), (e) the attendant's name, (f) the entry supervisor's name and signature, (g) hazards in the space, (h) measures to isolate hazards, (i) acceptable atmospheric conditions, (j) results of initial AND periodic tests with tester's name and time, (k) rescue and emergency services info + how they'll be summoned, (l) communication procedures, (m) equipment provided, (n) any other relevant info, and (o) any additional permits (hot-work, etc.). The permit is good for ONE shift maximum. Cancelled permits are kept for at least 1 YEAR.

     Reference: 29 CFR 1926.1206

   • Entry supervisor — duties

     The Entry Supervisor (1926.1208): knows the hazards including signs/symptoms of exposure; verifies tests have been conducted and procedures/equipment are in place BEFORE signing the permit; signs the permit to authorize entry; terminates entry and cancels the permit when work is complete OR when conditions change; verifies rescue services are available and can be summoned; removes unauthorized people; AND determines at intervals during entry that operations remain consistent with permit terms.

     Reference: 29 CFR 1926.1208

   • Attendant — never enters, never leaves

     The Attendant (1926.1209) stays OUTSIDE the space at all times during entry. Duties: knows hazards; recognizes signs of behavioral effects of exposure; maintains accurate count of authorized entrants; remains outside the space during entry until relieved; communicates with entrants; monitors activities inside and outside to determine if it is safe for entrants to remain; ORDERS EVACUATION if conditions change or entrants show effects of exposure; summons rescue services as needed; performs NON-ENTRY rescue if specified; keeps unauthorized people away. Critically — THE ATTENDANT NEVER ENTERS THE SPACE TO RESCUE. That is rescue-service work.

     Reference: 29 CFR 1926.1209

   • Authorized entrant — duties + alert criteria

     The Authorized Entrant (1926.1207-1) knows hazards including modes of exposure, signs and consequences. Duties: uses required equipment properly; communicates with attendant; ALERTS attendant whenever the entrant recognizes a warning sign or symptom OR detects a prohibited condition; AND EXITS THE SPACE AS QUICKLY AS POSSIBLE if ordered, if a warning condition is detected, or if the alarm sounds. Entrants must know they have STOP-WORK AUTHORITY for themselves the moment they sense a problem.

     Reference: 29 CFR 1926.1207

   Practice questions (2)

   1. 1. Maximum duration a permit-required confined-space entry permit can be valid for?

      • A.1 hour
      • B.8 hours
      • C.One shift✓ correct
      • D.Until the work is complete

      Per 1926.1206 permits are valid for one shift maximum, even if work is incomplete. A new permit must be issued for the next shift to ensure tests, conditions, and personnel are re-verified. "Until work is complete" is the most common multi-day misuse.

   2. 2. An entrant collapses inside a permit-required space. The attendant is alone outside. Correct action?

      • A.Enter the space and pull the entrant out
      • B.Summon rescue services + perform NON-ENTRY rescue (e.g., retrieve via tripod/winch); never enter✓ correct
      • C.Wait for the supervisor to arrive
      • D.Try to talk the entrant out

      The attendant NEVER enters — entering would create a second victim (the leading cause of multiple-fatality confined-space events). Non-entry rescue using a tripod/winch attached to the entrant's harness is the attendant's tool. Rescue services (entry rescue) are summoned for cases where non-entry rescue is not possible.

4. 04Rescue + multi-employer coordination

   ~60min

   The dirty secret of confined-space fatalities: 60%+ of victims are would-be rescuers. Knowing the difference between non-entry and entry rescue is what keeps the body count to one.

   • Non-entry rescue — the preferred mode

     Non-entry rescue uses retrieval equipment — typically a full-body harness with a retrieval line attached to a tripod-mounted winch above the space — so the attendant or rescuer can extract the entrant WITHOUT entering. Required for ALL permit entries unless the equipment would increase overall risk OR is not feasible. The retrieval line must be attached at the center of the entrant's back near shoulder level, above the head, or at any other location that creates a profile small enough for the smallest exit opening. EXCEPTION: vertical entries deeper than 5 feet require a mechanical retrieval device (winch).

     Reference: 29 CFR 1926.1211

   • Entry rescue — capable, equipped, available

     When non-entry rescue is not feasible, an entry rescue service must be in place BEFORE entry begins. The host employer must verify the rescue service is: CAPABLE (trained, drilled in this specific space configuration), EQUIPPED (atmospheric-monitoring gear, SCBA, retrieval gear, medical equipment), and AVAILABLE (can reach the space within a time that minimizes injury severity — typically 4-6 minutes for IDLH atmospheres). Calling 911 is NOT an automatic rescue plan; many fire departments are not trained or equipped for confined-space rescue and may refuse or take 20+ minutes.

     Reference: 29 CFR 1926.1211

   • Construction multi-employer coordination

     Subpart AA introduced FOUR roles for construction sites with multiple employers: HOST EMPLOYER (owns/operates the space), CONTROLLING CONTRACTOR (has overall responsibility for the construction work), ENTRY EMPLOYER (the one whose workers are entering), and RESCUE SERVICE. The host must inform the controlling contractor about all known confined spaces and their hazards. The controlling contractor must coordinate among entry employers and ensure they coordinate with each other. The entry employer must inform the controlling contractor of its program, hazards encountered, and any incidents. Information flows downhill — the entrant never bears the burden of asking around.

     Reference: 29 CFR 1926.1203(h)

   Practice questions (2)

   1. 1. A confined-space program lists "call 911" as the rescue plan. The local fire department is not certified for confined-space rescue. Compliant?

      • A.Yes — 911 is always sufficient
      • B.No — the rescue service must be VERIFIED capable, equipped, and available BEFORE entry✓ correct
      • C.Yes, if the entrant signs a waiver
      • D.Yes, if the entry is short

      Per 1926.1211, the host/entry employer must AFFIRMATIVELY VERIFY the rescue service is capable (trained for this specific space type), equipped (SCBA, retrieval gear), and available (response time minimizes injury). Listing "911" without that verification is non-compliant. Waivers do not override OSHA standards. Short entries face the same atmosphere risks.

   2. 2. Under Subpart AA, who is responsible for telling the controlling contractor about every known confined space and its hazards?

      • A.Authorized entrant
      • B.Attendant
      • C.Host employer✓ correct
      • D.Local OSHA office

      The host employer (typically the facility owner/operator) starts the information chain. The controlling contractor then coordinates among entry employers. The entrant and attendant operate at the working end of that chain — they are not responsible for original discovery. OSHA does not provide pre-entry hazard inventories.

External resources

• Official
  29 CFR 1926 Subpart AA — Confined Spaces in Construction ↗

  The construction-specific permit-required confined space standard, effective 2015. Read sections 1926.1202 (definitions), 1926.1203 (general requirements), 1926.1204-1211 (program requirements + roles + rescue) end-to-end.

• Official
  29 CFR 1910.146 — General Industry Permit-Required Confined Spaces ↗

  The general-industry standard. Construction Subpart AA largely mirrors this; differences are coordination-related. If your work crosses into general industry (factories, treatment plants), you live under 1910.146.

• Official
  OSHA Pub 3138 — Permit-Required Confined Spaces booklet ↗

  OSHA's plain-language summary booklet. Includes a sample entry permit and a decision-tree flowchart for confined-space classification — both worth printing and laminating for the field.