What it controls
- Atmosphere — is there flammable gas, vapour or dust; has it been tested?
- Distance and covering — have flammables been removed, and what could not be removed covered?
- Transfer paths — are openings, ducts and cable trays where sparks could fall closed off?
- Extinguishing — is an extinguisher ready, and who will use it?
- Attendant — mandatory in hazardous areas.
Measured thresholds
| Item | In the site procedure we measured |
|---|---|
| Distance to flammables | At least 15 metres |
| Explosive gas threshold | Stricter for hot work than for confined space entry |
| Attendant | Mandatory for all hot work in hazardous areas |
These values were measured from that site's own procedure; they are not universal thresholds. Your own values follow from your own risk assessment.
After the work stops
The most frequently skipped part of hot work is what happens afterwards: surfaces and hidden voids should be watched for a period before the area is left. A spark can start ignition long after the job ends, which is why the permit is closed by observation.
Relation to explosive atmospheres
Hot work in a classified explosive atmosphere cannot run on an ordinary hot work permit. That zone has its own rules and the permit sits on top of them rather than replacing them.
The contractor side
Hot work is often done by crews from outside. For a crew entering the site for the first time, the permit is also the only real briefing moment: which line is full, which tank was not emptied, which cover must stay closed.