CompEx: who needs it

The job spec looks good. Days, a food plant, motors, gearboxes, conveyors. Then one line near the bottom: "CompEx required".

You've never touched a chemical works in your life. So why would a bakery want it?

Then you get there and see the flour silos, the sifters and the dust extraction. Some of the motors carry a hexagon with "Ex" inside. The site has drawn zones on a plan, and the plan is pinned up by the maintenance office.

CompEx is the competence scheme for working on equipment in explosive atmospheres. Whether you need it depends far less on your trade than on where your work is.

Zones are the site's job

Under the Dangerous Substances and Explosive Atmospheres Regulations, DSEAR for short, the employer must sort places where an explosive atmosphere may occur into hazardous and non-hazardous. Hazardous places then get split into zones (regulation 7).

There are six zones, three for gas and three for dust (Schedule 2):

• Zone 0 and zone 20: the explosive atmosphere is there continuously, or for long periods, or frequently.
• Zone 1 and zone 21: it's likely to occur in normal operation, occasionally.
• Zone 2 and zone 22: it's not likely in normal operation, and if it does occur it won't last long.

The numbers in the 20s are dust. The schedule adds that layers and heaps of combustible dust count as a source too. That's the bit people forget when they blow down a dusty motor with an airline.

The zone sets what kit is allowed. Zone 1 or 21 needs category 1 or 2 equipment. Zone 2 or 22 can take category 1, 2 or 3 (Schedule 3). Swap a motor, a gland or a junction box for the wrong one and the protection has gone, even though the machine runs fine.

Where you'll meet it outside chemicals

Most people think of refineries and offshore. On manufacturing and logistics sites, zones turn up in less obvious places.

Dust is the big one. HSE says wood dust can explode if dispersed as a cloud, and a woodworking shop may need zone 22 areas, with only very limited need for zone 21 (HSE, ATEX FAQs). The same page notes that many food products, if tested, are explosive dusts. A shop handling sacks of flour usually doesn't need zoning. A food plant pumping flour or sugar through silos and sifters is a different story.

Aerosols are the logistics one. HSE accepts that an aerosol warehouse doesn't have to be zone 2, but only if an industry storage guide is followed very closely. If it isn't, the warehouse should normally be classed as zone 2.

Add solvent stores, paint and coating lines, and anywhere with flammable gas, and you'll see why a site you'd never call "chemical" can still ask for CompEx.

What the site has to give you

The duties here sit with the employer, but they shape your day.

DSEAR says that where a dangerous substance is present, employers must give their staff suitable information, instruction and training on the precautions to take (regulation 9). Before a workplace with hazardous zones is first used, someone competent in explosion protection must verify its overall explosion safety (regulation 7).

The code of practice, L138, gets practical. In areas where ignition could affect safety, the measures include inspection, testing, cleaning and maintenance regimes to stop equipment overheating or faulting. They also include making sure any portable equipment brought into hazardous areas is either suitably protected, or only brought in under a permit to work (L138, paragraph 241).

Think about what's in your hand. Your meter. Your phone. A cordless drill. A heat gun. On a zoned site, none of those go in without a permit unless they're rated for it. We cover the paperwork in permits to work and hot work permits.

So who needs it?

Here's our view.

You need CompEx if you install, inspect or maintain Ex electrical equipment in zoned areas as a regular part of your work. Electricians and instrument techs on chemical, pharma, fuel, distilling and some food and wood sites. That's who the scheme is built for. HSE's own FAQs mention electricians trained under the CompEx scheme to install ATEX equipment.

You should think about it if you're a mechanical fitter on those sites. Ex protection isn't only electrical. HSE notes there is a CompEx course and assessed qualification, Ex11, for non-electrical equipment, covering installation and inspection (HSE, ATEX FAQs). The same answer says anyone installing such equipment should at least understand hazardous area drawings and ATEX markings.

You probably don't need it if your work is packaging lines, conveyors and sorters on a dry-goods site with no zones. The site's DSEAR training, a permit and a clear plan of where the zones are will cover the odd job near one. Put the money into something you'll use every week, like IPAF and PASMA or a PLC course.

Why sites ask for it anyway

Look at it from the engineering manager's side.

Their dust extract fan has stopped at 2am. The motor sits in a zone 22 area. They need someone who'll replace like for like, keep the right glands, and not leave a gap in the protection. If they get it wrong, the risk is a fire or an explosion. A late trailer is the least of it.

So when they ring round for cover, CompEx is the quickest proof they can get. An engineer without it may be perfectly capable, but they can't show it in a two-minute phone call. On those sites the ticket really does decide who gets the shift.

Where it fits with your other tickets

CompEx sits on top of your trade. It won't make a fitter an electrician, and the electrical work still falls under the Electricity at Work Regulations. Electrical kit that could be exposed to flammable or explosive substances, dusts included, must be built or protected to prevent danger, so far as is reasonably practicable (regulation 6). See which tickets get you contract work for how it stacks up against the rest.

If you're electrical, get your 18th Edition and solid experience first. CompEx assumes you already know how to do the job safely on ordinary kit.

What to do on Monday

1. Ask your site for its hazardous area drawing. Find every zone you walk through on a normal shift.
2. Check the Ex marking on the motors and boxes you work on in those zones. If you don't know what it means, that's your answer about training.
3. Before you take any meter, phone or power tool into a zone, check whether it's rated or whether you need a permit.
4. If you work in zones every week, book CompEx. If you don't, spend the money elsewhere.

Paragraph numbers refer to L138, second edition (2013).