Purpose
This SOP establishes the procedure for safe entry into confined spaces in buildings. A confined space is any enclosed or partially enclosed area not designed for continuous occupancy that may have a hazardous atmosphere, limited entry/exit, or potential for engulfment. More people die attempting rescue in confined spaces than from the original incident.
Applicable Standards
- OSHA 29 CFR 1910.146 — Permit-Required Confined Spaces
- BS 6164 — Health and Safety in Tunnels and Confined Spaces
- AS 2865 — Confined Spaces (Australian Standard, widely adopted)
- ISO 45001 — Occupational Health and Safety
Confined Spaces in Buildings
- Water tanks — overhead, underground, break tanks
- Sewage/drainage chambers — manholes, pump stations, grease traps
- Duct systems — large HVAC ducts accessible for maintenance
- Lift pits — bottom of lift shafts
- Basement voids — cable basements, service tunnels
- Ceiling voids — accessible ceiling spaces with limited ventilation
- Generator exhaust chambers
- Fire pump rooms — below grade with limited ventilation
- Transformer vaults
Entry Procedure
| Step | Action | Who | Critical Detail |
|---|---|---|---|
| 1 | Risk assessment | Competent Person | Identify ALL hazards: atmosphere, engulfment, mechanical, electrical, biological |
| 2 | Can entry be avoided? | Competent Person | If the task can be done without entry (cameras, remote tools), do not enter |
| 3 | Issue entry permit | Permit Issuer | Specific to this space, this task, this time window |
| 4 | Isolate hazards | Entry Supervisor | LOTO all mechanical/electrical, isolate pipework, ventilate space |
| 5 | Test atmosphere | Entry Supervisor | O2: 19.5-23.5%. LEL: below 10%. H2S: below 10ppm. CO: below 25ppm. |
| 6 | Set up rescue equipment | Entry Supervisor | Retrieval system (tripod + winch), SCBA, first aid, communication |
| 7 | Assign standby person | Entry Supervisor | SOLE job is to monitor entrant and summon rescue. Never enters the space. |
| 8 | Enter and work | Entrant | Continuous atmosphere monitoring. Exit immediately if alarm sounds. |
| 9 | Exit and close permit | Entry Supervisor | Confirm all persons out, tools removed, space secured, permit closed |
Atmosphere Testing
| Gas | Safe Range | Action Level | Danger |
|---|---|---|---|
| Oxygen (O2) | 19.5-23.5% | Below 19.5% or above 23.5% | Below 16% = impaired judgment. Below 10% = unconsciousness in seconds. |
| LEL (flammable) | Below 10% LEL | Above 10% LEL = evacuate | Above 100% LEL = explosion risk |
| H2S | Below 10 ppm | Above 10 ppm = evacuate | Above 100 ppm = rapid incapacitation |
| CO | Below 25 ppm | Above 25 ppm = evacuate | Above 400 ppm = life-threatening in 1 hour |
Testing sequence: Test at top, middle, and bottom of the space. Heavier gases (H2S) settle at the bottom. Lighter gases (methane) rise to the top.
The Rescue Rule
NEVER enter a confined space to rescue someone. This is the most important rule in confined space safety.
- 60% of confined space fatalities are rescuers who entered without breathing apparatus.
- The atmosphere that incapacitated the first person will incapacitate the rescuer.
- Rescue must be performed with SCBA (Self-Contained Breathing Apparatus) and retrieval equipment.
- If your rescue plan is "go in and get them", you do not have a rescue plan.
- Call emergency services. Use the retrieval system (tripod/winch) to extract the person.
Standby Person Requirements
- Positioned at the entry point at all times
- Sole duty is to monitor the entrant and summon rescue if needed
- Must NOT perform any other work
- Must NOT enter the confined space under any circumstances
- Must have communication with the entrant (voice, radio, or visual)
- Must know how to activate the rescue plan
- Must be trained in confined space awareness
References
Insights & Guidance
- NEVER enter a confined space to rescue someone. 60% of confined space fatalities are would-be rescuers.
- Test atmosphere at top, middle, and bottom: O2 19.5-23.5%, LEL below 10%, H2S below 10ppm, CO below 25ppm.
- Standby person at entry point at all times. Their sole job is to monitor and summon rescue. They must never enter.
- If the task can be done without entry (cameras, remote tools), do not enter.
- 9-step procedure: risk assessment, avoid entry, permit, isolate, test atmosphere, rescue setup, standby, enter, close.
Confined space incidents kill quickly and silently. Toxic gases are often invisible and odourless. A person can lose consciousness in seconds. The instinct to rush in and rescue causes the majority of confined space deaths.
- No atmosphere testing — invisible gases (CO, H2S, oxygen depletion) cause rapid incapacitation.
- Rescue attempt without SCBA — rescuer becomes the second victim.
- No standby person — incapacitated entrant has no one to call for help.
- Confined space register (list of all confined spaces on site)
- Entry permit forms (completed for each entry)
- Atmosphere test records
- Rescue plan and equipment inspection records
- Is a standby person posted at the entry point?
- Is atmosphere monitoring equipment in use?
- Is rescue equipment (tripod, winch, SCBA) on site?
- Do you have a confined space register?
- What is your rescue plan for confined space incidents?
- Are gas detectors calibrated and in date?
- Confined space risk assessment — occupational hygienist.
- Rescue planning — confined space rescue team.
- Gas monitoring equipment — calibration/rental supplier.