Guide
DSEAR hazardous area classification: zones, drawings and signs
Updated
Zoning is the part of DSEAR that costs money and the part that everything else hangs off. Get the zones wrong and the equipment specification, the signage and the permit regime are all wrong with them.
What regulation 7 requires
Where an explosive atmosphere may occur in quantities such as to endanger people, regulation 7 requires the employer to classify those hazardous places into zones in accordance with Schedule 2, to apply the requirements in Schedule 3 to equipment and protective systems, and to mark the points of entry to those places with signs in accordance with Schedule 4 (legislation.gov.uk).
The six zones, as Schedule 2 defines them
| Zone | Definition |
|---|---|
| Zone 0 | A place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapour or mist is present continuously or for long periods or frequently |
| Zone 1 | A place in which such an explosive atmosphere is likely to occur in normal operation occasionally |
| Zone 2 | A place in which such an explosive atmosphere is not likely to occur in normal operation but, if it does occur, will persist for a short period only |
| Zone 20 | A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is present continuously, or for long periods or frequently |
| Zone 21 | A place in which such a dust cloud is likely to occur in normal operation occasionally |
| Zone 22 | A place in which such a dust cloud is not likely to occur in normal operation but, if it does occur, will persist for a short period only |
Wording condensed from Schedule 2 to the Dangerous Substances and Explosive Atmospheres Regulations 2002 (legislation.gov.uk). The 0, 1 and 2 series covers gas, vapour and mist; the 20, 21 and 22 series covers combustible dust.
Why drawings drive the fee
- Classification is a technical exercise: every source of release has to be identified, its grade judged and the extent of the resulting hazardous area worked out.
- The output is normally a set of drawings showing zone boundaries in plan and often in elevation. Producing those from scratch is the largest single item in most DSEAR quotes.
- Existing drawings can usually be reviewed and updated far more cheaply, which is why assessors ask whether you have them before pricing.
- Plant changes invalidate zoning. A new vent, a relocated tank or a change of solvent moves boundaries, and regulation 5(3) requires the assessment to be reviewed after significant change.
What zoning then obliges you to do
- Equipment. Regulation 7(2) applies the Schedule 3 requirements to equipment and protective systems in classified places, so the zone decides what may be installed and used there.
- Signage. Regulation 7(3) requires the points of entry to classified places to be marked with signs in accordance with Schedule 4.
- Records. Where five or more people are employed, the zone classification and the verification of explosion safety form part of the significant findings recorded under regulation 5(4).
- Working practices. Permits, ignition source control and maintenance procedures all take their boundaries from the zone plan, which is why an out of date drawing is a live risk rather than a paperwork problem.
Ask any prospective assessor whether hazardous area classification is included in their price, and in what form you receive the drawings. It is the single most common reason two DSEAR quotes are not comparable.