Compex - zones

Question 1

What are gas zones?

Answer 1

Gas zones are a way to classify locations where flammable gases or vapors may create an explosive atmosphere. The “zone” indicates how often and how long that explosive atmosphere can be present, which then dictates the minimum protection level for equipment installed there (per IEC/ATEX).

Question 2

What is zone 0 ?

Answer 2

An explosive gas atmosphere is present continuously, for long periods, or frequently.

Frequency: >1000 hours/year or continuous

Typical examples: inside tanks or vessels containing flammable liquids, the vapor space above liquid in a closed tank

Question 3

What are the three zone classifications?

Answer 3

Zone 0, 1 and 2

Question 4

What is zone 1?

Answer 4

An explosive gas atmosphere is likely to occur in normal operation.

Frequency: 10–1000 hours/year (likely in normal operation).

Typical examples: near pump seals, vents, sampling points, relief valves, loading/unloading points.

Question 5

What is zone 2?

Answer 5

An explosive gas atmosphere is not likely in normal operation; if it occurs, it exists only for a short time.

Frequency : <10 hours/year and brief/abnormal.

Typical examples: areas surrounding Zone 1 equipment, well‑ventilated spaces where releases are infrequent and brief.

Question 6

What is the atex category and EPL for zone 0?

Answer 6

Zone 0 → ATEX Category 1G → EPL Ga (minimum).

Higher protection is always acceptable in lower zones (Ga is also fine in Zones 1 and 2).

Question 7

What is the atex category and EPL for zone 1?

Answer 7

Zone 1 → ATEX Category 2G (or 1G) → EPL Gb (or Ga).

Minimum is Gb/2G; Ga/1G is also acceptable. Gc/3G is not.

Question 8

What is the atex category and EPL for zone 2?

Answer 8

Zone 2 → ATEX Category 3G (or 2G/1G) → EPL Gc (or Gb/Ga).

Minimum is Gc/3G; higher levels are acceptable.