# ATEX Zones Explained: Which Radio for Zone 0, 1 or 2?
Here is a question worth asking your site team.
Do you know which zone your workers carry radios into?
If the answer is a shrug, that is the real problem. Everything else follows from the zoning.
## Who decides the zone
Not the radio supplier. Not the manufacturer.
Under DSEAR — the Dangerous Substances and Explosive Atmospheres Regulations 2002 — the duty sits with the employer. You are required to assess the risk from explosive atmospheres and classify the places where they may occur.
That classification produces a hazardous area drawing. It marks out zones. Everything you then bring onto the site has to match.
If you do not have that drawing, no radio purchase is going to fix the underlying gap.
## The gas zones
Zoning is about how often a dangerous atmosphere is present, not how bad it would be.
**Zone 0** — present continuously, for long periods, or frequently. Think the vapour space inside a solvent tank.
**Zone 1** — likely to occur in normal operation, occasionally. Around a filling point, a sampling station, a pump seal.
**Zone 2** — not likely in normal operation, and if it does occur, only for a short period. The wider area around a Zone 1, or a space that only becomes dangerous when something fails.
## The dust zones
The same logic, with a 2 in front.
**Zone 20** — continuously or frequently. Inside a silo or a dust collector.
**Zone 21** — likely in normal operation. Around a bagging point or a transfer chute.
**Zone 22** — not likely in normal operation. Surrounding areas where dust layers may build.
Dust deserves more respect than it usually gets. Flour, sugar, custard powder, aluminium, wood, coal. All have caused fatal explosions.
## Which radio goes where
The category number on the radio maps straight onto the zone.
| Zone | Gas category | Dust category | Protection level |
|---|---|---|---|
| 0 | 1G | — | ia (Ga) |
| 1 | 2G | — | ib (Gb) |
| 2 | 3G | — | ic (Gc) |
| 20 | — | 1D | ia (Da) |
| 21 | — | 2D | ib (Db) |
| 22 | — | 3D | ic (Dc) |
Equipment certified for a more demanding zone is fine in a less demanding one. A Zone 1 radio works in Zone 2. It does not work in Zone 0.
## What this means in practice
Nearly every ATEX handheld sold in the UK is **category 2**, marked **II 2G Ex ib**. Zone 1 and Zone 2.
The Motorola R7Ex, the Entel DT900 series, the Hytera HP715Ex. All Zone 1 equipment.
If you genuinely have people working in Zone 0, you need **category 1** equipment marked **Ex ia**. That is a much shorter list. The Hytera PD715IS and PD795IS are two of them.
Here is the honest position, though. Zone 0 is rare as a place where a person stands. It is usually the inside of a vessel. Most "we need Zone 0 radios" conversations turn out, on inspection, to be Zone 1.
Worth checking before you spend the difference.
## The mistake I see most
A site buys correctly for the process area, then forgets the boundary.
Workers walk from the office, through the plant, into the zone. The radio goes with them. Fine.
Then a contractor arrives with a standard commercial handheld, because nobody told them.
Zoning only protects you if the control extends to everyone who crosses the line. That means signage, induction, and a visible way to tell an approved radio from an ordinary one. This is exactly why most ATEX radios are bright blue.
## Getting it right
Three things, in order.
1. Get your hazardous area classification drawing out and look at it.
2. Identify which zones your people actually enter carrying a radio.
3. Match the category, then the gas group, then the temperature class.
Do those in that order and the shortlist writes itself.
Skip step one and you are guessing with people's lives.
Craig