Confined Space Safety: Permits, Gas Testing and Rescue

Tanks, pits, tunnels, silos, manholes and ducts all look different, but they share a danger: they are not designed for people to stay in, and the air inside can change without warning. Confined space accidents are often fatal, and many victims are colleagues who rushed in to help.

What makes a space "confined"?

A confined space is large enough to enter but has limited entry or exit, is not designed for continuous occupation, and may contain or develop a hazardous atmosphere or other danger.

The main hazards

• Low oxygen caused by rust, fermentation or displacement by other gases.
• Toxic gases such as hydrogen sulphide and carbon monoxide.
• Flammable vapours that can ignite from a spark.
• Engulfment in liquids or loose material such as grain or sand.
• Heat, noise and poor visibility.

Step 1: Avoid entry where possible

Can the job be done from outside using cameras, long-handled tools or robotics? If yes, do not enter.

Step 2: Use a permit-to-work system

A permit confirms that the space has been isolated, cleaned, ventilated, tested and that rescue arrangements exist before anyone enters. Training in a Permit to Work System helps supervisors issue and close permits correctly.

Step 3: Isolate and ventilate

Disconnect pipes, lock off power and mechanical equipment, and ventilate the space. Never use oxygen to "freshen" the air; it makes fire far more likely.

Step 4: Test the atmosphere

Test before entry and keep monitoring while people work. Only trained people should use gas detectors; see our Authorised Gas Testing Training.

Step 5: Appoint a standby person

A trained attendant stays outside, keeps contact with the entrants and raises the alarm. They must never enter to attempt a rescue.

Step 6: Plan the rescue

Rescue arrangements must be in place before the first person goes in: breathing apparatus, retrieval lines and trained rescuers. The most important rule is that untrained people never enter to help.

Get trained

Our Confined Space Safety course covers these steps in detail. Contact a branch to arrange training for your team.

Warning signs that something is wrong

• Dizziness, headache, nausea or unusual drowsiness.
• Gas detector alarms or a sudden change in readings.
• Strange smells, although some deadly gases cannot be smelled.
• Loss of contact with the person inside.

If any of these happen, the entrant should leave immediately and the standby person should raise the alarm and follow the rescue plan.

Toolbox talk checklist

• Is entry really necessary?
• Is the permit signed and displayed?
• Has the space been isolated, cleaned and ventilated?
• Has the atmosphere been tested, and will it be monitored?
• Is the standby person in place and is the rescue equipment ready?

Frequently asked questions

Is a manhole a confined space?

Often yes. If it has limited entry and exit and a hazardous atmosphere could develop, treat it as a confined space until assessed.

Can I check the air with a lighter or by smell?

Never. Use a calibrated gas detector operated by a trained person, because many dangerous gases are odourless or invisible.

Who can act as the standby person?

A trained, competent person who stays outside, keeps contact with entrants and knows the emergency plan. They must not enter to attempt a rescue.