Paint, powder and print

Spray booths, mixing rooms and coating

The booth is usually the best-controlled part of the process. The mixing bench and the gun washer next to it usually are not.

HIGH-LEVEL VENT LOW-LEVEL VENT ZONE 0 vapour space in the drum ZONE 1 ZONE 2 INDICATIVE ONLY · ACTUAL EXTENTS DEPEND ON RELEASE RATE, VENTILATION AND SUBSTANCE
Vapour zoning around a release source

Where we actually find the risk

01

The mixing area

Open containers, decanting, weighing and stirring, often on a bench in the main workshop with no dedicated extract and an ordinary socket at head height.

02

Gun cleaning

Solvent washers are a continuous release source. Lid closed or open makes a large difference and the lid is almost never closed.

03

Ventilation as built vs as running

Booth airflow rates drift as filters load. The zoning that made sense at commissioning may not describe the booth you have now.

04

Filters and extract ducting

Overspray accumulation is both a fire load and, in powder work, a dust explosion risk inside the ducting.

05

Storage

Where the paint, thinners and hardeners live between jobs, and whether the quantity in the workroom has crept up over the years.

06

Hot work nearby

Grinding and welding in the same building as a solvent store is a permit question, and permits that stop at the workshop door do not help.

Powder coating is a different problem

Powder is a combustible dust, not a vapour. That changes the zone numbers, the equipment categories and the controls that matter.

The risk concentrates inside the plant rather than in the room: the booth, the recovery cyclone, the filter unit and the ducting between them. Housekeeping matters more than most operators expect, and compressed air used for cleaning down makes things considerably worse.

More on combustible dust →

Photo slot — booth or mixing room
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Questions

Is a spray booth automatically a zoned area?

Inside the booth, during spraying, almost always. The interesting question is what happens outside it: at the door, at the filter face, at the mixing bench and around the gun cleaner. That is where the zoning argument is usually won or lost.

Our booth was certified when it was installed. Are we covered?

The booth being suitable is not the same as the room being assessed. Booth certification tells you about the booth. DSEAR asks about the whole workplace, including where you mix, where you store and where the extract discharges.

What about powder coating?

Powder is a combustible dust, so it is a dust zoning question rather than a vapour one. Zone 20, 21 or 22 rather than 0, 1 or 2, and the ignition sources that matter are different.

Does gun cleaning count?

Very much so. Gun washers and solvent cleaning stations are a classic release source, frequently sited in a corner with no extract and an ordinary socket above them.

Tell us what you store and we'll tell you where you stand

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