Class 1 Division 1 vs Division 2 Explosion-Proof Lighting: What the Ratings Mean
What Class I Division 1 and 2 mean for LED lighting, how they map to Zones 0, 1 and 2, gas groups A–D, T-codes, listing rules and choosing fixtures for each market.
Key points
- Class I covers flammable gases and vapours; Division 1 is where they are present in normal operation, Division 2 only in abnormal conditions.
- Roughly, Division 1 covers Zone 0 and Zone 1, and Division 2 corresponds to Zone 2, but the systems are not interchangeable without checking the code.
- Groups A–D (A acetylene, B hydrogen, C ethylene, D propane) and a T-code set which fixtures can be used.
- In the USA and Canada, fixtures must be listed by a recognised testing laboratory for Class/Division or Zone use; an IECEx or ATEX certificate alone is usually not accepted there.
Engineers in the oil, gas and chemical industries meet two systems for hazardous areas: the North American Class/Division system and the international Zone system. Lighting specifications for the same type of plant can look very different depending on where it is. This guide focuses on Class I Division 1 and 2 for LED lighting and how they relate to Zones.
Classes: what kind of hazard
| Class | Hazard | Examples |
|---|---|---|
| Class I | Flammable gases and vapours | Refineries, fuel stations, paint booths, chemical plants |
| Class II | Combustible dust | Grain silos, flour mills, coal, sugar, metal dust |
| Class III | Ignitable fibres and flyings | Textile mills, cotton gins, woodworking |
This article covers Class I.
Divisions: how often the hazard is present
| Division 1 | Division 2 | |
|---|---|---|
| Hazard present | In normal operation, or frequently during maintenance or leaks | Only in abnormal conditions |
| Examples | Inside spray booths, around open dip tanks, pump pits, near vents | Areas next to Division 1, enclosed areas where vapours only escape by accident |
| Fixture protection | Explosion-proof (flameproof), or equivalent | Explosion-proof, or non-sparking/non-incendive designs listed for Division 2 |
Groups for Class I
| Group | Typical gas | Zone system equivalent |
|---|---|---|
| A | Acetylene | IIC |
| B | Hydrogen | IIC (IIB + H2) |
| C | Ethylene | IIB |
| D | Propane, gasoline, natural gas | IIA |
A fixture listed for Groups C and D cannot be used where hydrogen or acetylene may be present.
Temperature codes
The T-code sets the maximum surface temperature, and it must be below the ignition temperature of the gas:
| T-code | Max surface temperature |
|---|---|
| T1 | 450 °C |
| T2 | 300 °C |
| T3 | 200 °C |
| T4 | 135 °C |
| T5 | 100 °C |
| T6 | 85 °C |
North American codes also use subdivisions such as T2A–T2D and T3A–T3C. LED fixtures often achieve T4–T6, which is one of their advantages over hot HID lamps.
How Divisions map to Zones
| North America | International (IEC / ATEX) |
|---|---|
| Class I Division 1 | Zone 0 and Zone 1 |
| Class I Division 2 | Zone 2 |
| Class II Division 1 | Zone 20 and Zone 21 |
| Class II Division 2 | Zone 22 |
The mapping is approximate. Zone 0 (hazard present continuously) is stricter than most Division 1 equipment allows; the NEC sets rules for which marking can go where. For the international system in detail, see our guide to explosion-proof light ratings.
Listing and certification
- USA and Canada: fixtures must be listed by a Nationally Recognized Testing Laboratory (UL, CSA, ETL, FM and others) for the class, division (or zone), group and T-code. Standards include UL 844 for luminaires in hazardous locations and UL 1203 for explosion-proof equipment.
- Rest of the world: IECEx, ATEX in Europe, or national schemes based on IEC 60079, such as GB 3836 in China.
A fixture with only an IECEx or ATEX certificate is not normally acceptable for a US or Canadian site, and a fixture with only a UL listing may not be acceptable in Europe or the Middle East. Check what the project’s authority requires before choosing products.
Our explosion-proof range is certified to the Zone system: the BED series under GB 3836 (aligned with IEC 60079) in our own name, and other models such as the BDE507 with the certificate supplied with the quotation. They suit Zone-based projects in Asia, Africa, the Middle East and Latin America. For North American Class/Division projects, ask us before specifying, as a local listing is needed.
Typical fixtures by area
| Area | Typical fixture |
|---|---|
| Spray booth interior (Div 1 / Zone 1) | Explosion-proof linear or panel light, often outside a sealed window |
| Pump room (Div 1 or 2) | Explosion-proof ceiling light or high bay |
| Process units outdoors | Explosion-proof floodlights and area lights |
| Tank farm | Explosion-proof floodlights on poles |
| Control room next to hazardous area | Standard lighting, if classified safe |
| Escape routes in hazardous area | Explosion-proof emergency lights |
Installation differences
- Division 1 in the US: threaded rigid conduit with seals within a set distance of each fixture, or listed cables and glands
- Zone installations: certified cable glands matched to the protection type and cable
- Both: earthing, closed unused entries, and inspection before energising
Mixing systems on one site needs careful documentation so maintenance teams know which rules apply to which equipment.
Choosing fixtures
- Get the area classification drawing: class, division or zone, group, T-code
- Confirm which certification the authority accepts
- Choose light level and fixture type for the task, as for any lighting design
- Check the fixture’s marking covers the area, including ambient temperature
- Check corrosion protection for the environment (WF1/WF2 for chemical and coastal)
- Plan maintenance: openings in hazardous areas need permits, so long-life LED fixtures reduce work
LED benefits in hazardous areas
- Lower surface temperatures, so better T-codes
- Instant start after power interruptions
- Long life, fewer openings for maintenance
- 50–70% less energy than HID
Ordering for Zone-based projects
Send the zone drawing, gas group, temperature class, mounting heights, light levels and the certificate type required. We will propose certified fixtures and a layout.
Sources
Frequently asked questions
What does Class 1 Division 1 mean?
Under the US National Electrical Code, Class I locations contain flammable gases or vapours. Division 1 means an ignitable concentration can exist during normal operation, for example inside spray booths or around open process equipment.
What is the difference between Division 1 and Division 2?
In Division 1 the hazard is present in normal operation; in Division 2 it is only present if something goes wrong, such as a leak or equipment failure. Division 2 allows fixtures with less protection, such as non-sparking designs, but they must still be listed for it.
Can Zone-certified lights be used in Class I Division 2 areas?
In the USA, the NEC allows the Zone system (Article 505) as an alternative, and some Zone-marked equipment is permitted in Division areas under specific conditions. Equipment must be listed for US use. For projects outside North America, IECEx, ATEX or national Zone certificates are normally used instead.