A confined space is large enough for a person to enter and work, has limited ways in or out, and is not designed for continuous occupancy. Tanks, silos, manholes, pits, ducts and vessels all qualify. Many fatalities happen because someone entered "just for a minute" — and a second person followed to help.
Why confined spaces are so dangerous
- Oxygen deficiency from rust, fermentation or inert gas purging
- Toxic gases such as hydrogen sulphide and carbon monoxide
- Flammable atmospheres from vapours, solvents or residues
- Engulfment by grain, sand or liquid
- Heat, noise and poor visibility
Step 1: Avoid entry where possible
The best control is not going in. Can the work be done from outside with long-handled tools, cameras or robotic cleaning? Only if the answer is no should entry be planned.
Step 2: Risk assessment and permit to work
A competent person assesses the space and the task, then a confined space entry permit is issued. A good permit records the location, task, duration, hazards, isolation, gas test results, required PPE, the names of entrants and attendant, and the rescue arrangements. The permit expires at the end of the shift and is cancelled when work stops.
Step 3: Isolation
All pipes, power and moving parts are isolated, locked and tagged. Blanking or disconnecting lines prevents hazardous material flowing in.
Step 4: Atmospheric testing
Test with a calibrated multi-gas detector before entry and keep monitoring during the work. Test at top, middle and bottom because gases stratify. Typical checks are oxygen, flammable gas (as a percentage of the lower explosive limit), hydrogen sulphide and carbon monoxide. Never rely on smell.
Step 5: Ventilation
Use mechanical ventilation to supply fresh air and dilute contaminants. Position the intake away from exhaust fumes.
Step 6: People and roles
- Entrant — trained, fit and equipped.
- Attendant (standby person) — stays outside, keeps communication, counts entrants, and never enters to rescue.
- Entry supervisor — verifies the permit conditions before entry.
Step 7: Rescue planning
Rescue must be planned before entry. Use a harness and lifeline with a tripod or winch for vertical entries and keep suitable breathing apparatus ready. Practise the rescue regularly.
Key takeaway: Test, ventilate, permit, attend and plan the rescue. If anything changes, everyone gets out.
Frequently asked questions
Who can sign a confined space permit?
A trained and authorised person defined in your procedure, usually an entry supervisor or permit issuer.
Can I enter if the gas reading looks normal?
Only if the permit conditions are met, monitoring continues, and an attendant and rescue plan are in place.
Get certified with our Confined Space Entry and Rescue course.