A confined space entry checklist is what the entry supervisor works through before anyone goes into a tank, pit, vessel, sewer, silo or chamber: is the space isolated, is the air safe and recorded as safe, is someone posted at the opening, and can the entrant be got out if things go wrong. This one records every gas reading with its time and depth, and if any reading is outside limits it will not let the entry be authorised. You can fill it in here and download a finished PDF without creating an account.
Why confined spaces kill people who know better
The danger in a confined space is usually invisible. The air can be short of oxygen, rich in a flammable gas, or carry a toxic one like hydrogen sulphide that deadens the sense of smell at the concentrations that matter. A space can also fill — grain, sludge, water — faster than anyone can climb out.
The pattern that recurs in fatal incidents is the second victim: somebody sees a colleague collapse and goes in after them without breathing apparatus. That is why the rescue plan here is its own section, and why the attendant's first job is to raise the alarm, not to go in.
Test in order, record every reading
Test the air from outside, before the space is opened wider than needed, with a gas detector that has been bump tested that day. The usual order is oxygen first, then flammable gas, then toxic gases — a flammable reading is unreliable if there is not enough oxygen for the sensor to work properly.
Test at more than one depth. Some gases are heavier than air and pool at the bottom; others rise. A reading at the manhole lid tells you about the manhole lid.
Record each reading with its time and position. "Atmosphere tested — OK" does not survive an investigation; a row reading 09:40, bottom, O2 20.9%, LEL 0%, H2S 0 ppm, CO 2 ppm does.
The numbers people use, and why yours may differ
Your permit or your site procedure sets the acceptable limits, and they override anything here. The values below are commonly used reference points, drawn mainly from US practice — where OSHA's permit-space rule, 1910.146, treats oxygen outside 19.5–23.5% or flammable gas above 10% of its lower explosive limit as a hazardous atmosphere:
- Oxygen — commonly 19.5% to 23.5%. Normal air is about 20.9%; a falling reading means something is displacing it.
- Flammable gas — commonly below 10% of the lower explosive limit, and many sites set a lower alarm.
- Hydrogen sulphide — commonly a single-figure ppm limit, set by the local exposure limit.
- Carbon monoxide — commonly somewhere around 25–35 ppm, again set by the local exposure limit.
A failed reading is a hard stop
If any reading is outside the limits on the permit, nobody goes in. Ventilate, find out why, and test again — and record the new readings as new rows, rather than overwriting the ones that failed.
On this form, choosing "one or more readings outside limits" hides the authorisation question and the entry log and puts a stop instruction in their place. The entry cannot be signed for until a fresh set of readings is entered and every one of them is within limits.
This checklist and the permit
In most regimes the permit is the legal authorisation and this checklist is the evidence behind it. Many sites attach the PDF to the permit, or use it as the permit where their procedure allows. Either way, the permit should be posted at the entry for as long as anybody is inside, and kept afterwards — in the US, cancelled permits are kept for at least a year for the annual programme review.
Common questions
What is a permit-required confined space?
A space large enough to enter, with limited ways in and out, not designed for people to stay in, that also has a serious hazard — a dangerous atmosphere, a risk of engulfment, a shape that could trap someone, or another serious hazard. That is the US definition; UK and Australian law use similar ideas with different wording.
Who can authorise a confined space entry?
The entry supervisor named on the permit — someone trained in the hazards of that space, who checks that the conditions on the permit are met before signing, and who can stop the entry at any time.
What gases should be tested before entry?
At minimum oxygen, flammable gas, and the toxic gases you could reasonably expect — commonly hydrogen sulphide and carbon monoxide, which is why four-gas detectors are standard. Add others where the space has held something specific, such as ammonia or solvents.
Does the attendant need to stay at the entrance the whole time?
Yes. The attendant stays outside, keeps count of who is in, stays in contact with them, watches for signs of trouble, and summons rescue. They do not enter to attempt a rescue unless they are relieved and the rescue plan provides for it.
Can I rely on the fire service for rescue?
Only if you have confirmed in advance that they can reach you in time, have the right equipment, and will come for this kind of space. Many cannot respond fast enough for an atmospheric emergency, which is why most plans put trained rescuers and a retrieval system at the opening.
How often should the air be re-tested?
Continuously for as long as anyone is inside, with a personal or area monitor, and with a fresh recorded test after any break in work or any change — new work starting inside, ventilation stopped, a new shift.