UL 844: Standard for Hazardous Location Lighting
UL 844 is the US safety standard for luminaires used in hazardous (classified) locations, where flammable gases, vapours, combustible dust or ignitable fibres may be present. Its full title is Luminaires for Use in Hazardous (Classified) Locations, and UL Standards & Engagement publishes it as ANSI/UL 844.
The current edition is the thirteenth, published on 29 June 2012 and last revised on 11 October 2021. It covers fixed and portable luminaires in the Class and Division system of the National Electrical Code (NFPA 70), and in Class I Zones 1 and 2 and Zones 20, 21 and 22.
Why Hazardous Location Luminaires Need Their Own Standard
A luminaire brings two ignition sources into a hazardous area: arcs and sparks from its electrical circuits, and hot surfaces from its light source and driver. General lighting standards do not control either for a flammable atmosphere, so this standard adds requirements that do.
The principle is containment and temperature. An explosionproof enclosure must withstand an explosion of a specified gas inside it, stop that explosion igniting the atmosphere around it, and run cool enough not to ignite that atmosphere itself.
The test programme follows from that. In the March 2019 text the main performance tests are:
- Temperature test (clause 25): surface temperatures, judged at a 40°C ambient unless the luminaire is marked for a higher one.
- Explosion tests (clause 26): at least 15 tests on each enclosure, using specified gas mixtures.
- Hydrostatic pressure test (clause 28), repeated as a production test under clause 73.
- Dust penetration and dust-tight enclosure tests (clauses 29, 29A and 49).
- Thermal shock, vibration and rust resistance, plus drop and impact tests for portable luminaires.
Need help or a quotation?
Email us at info@betalight-tactical.com. Give us the class, division or zone, the group and the temperature code your site requires, so we can check what a product’s certificate actually states before we quote.
UL 844 Hazardous Location Classifications
The standard follows the classification the National Electrical Code gives an area. The class names the type of hazard, the division how likely it is to be present, and the group the specific material. A luminaire must be listed for all three.
Class I: Flammable Gases and Vapours
- Division 1: hazardous concentrations may exist under normal operating conditions, or often during repair and maintenance.
- Division 2: the liquids or gases are normally confined in closed containers or systems, or kept out by positive mechanical ventilation, and escape only through accident or abnormal operation.
- Groups: A (acetylene), B (hydrogen and similar), C (ether and similar), D (propane, butane, gasoline, natural gas).
- Examples: oil refineries, gas plants and chemical plants.
Division 1 does not mean the gas is present all the time. Normal operation, frequent repair and maintenance, or a breakdown that releases gas is enough, which is why Class I, Division 1 lighting is the most demanding case in Class I. Continuous presence is what the Zone system separates out as Zone 0.
Class II: Combustible Dust
- Division 1: dust is, or may be, in suspension in the air under normal operating conditions in ignitable quantities, or the dust is electrically conductive.
- Division 2: dust is not normally in suspension, but may be through infrequent malfunction of handling or processing equipment.
- Groups: E (metal dusts such as aluminium and magnesium), F (carbon black, charcoal, coal and coke dust), G (grain, flour, starch, cocoa and similar).
- Examples: grain silos, flour mills and metal processing facilities.
Check the group against the scope. UL 844 covers Groups E, F and G in Division 1, but only Groups F and G in Division 2.
Class III: Ignitable Fibres and Flyings
- Division 1: easily ignitable fibres, or materials producing combustible flyings, are handled, manufactured or used.
- Division 2: such fibres are stored or handled, other than in the process of manufacture.
- Examples: textile mills, cotton gins, flax processing plants and woodworking plants that produce sawdust and flyings.
Divisions and Zones
The NEC offers a second system for the same hazards. Article 505 divides Class I gas locations into Zones 0, 1 and 2, and Article 506 covers dust and fibres as Zones 20, 21 and 22. OSHA allows employers to use Zones instead of Divisions for gases and vapours (29 CFR 1910.307(g)).
Zone 0 is where gas is present continuously or for long periods, Zone 1 where it is likely in normal operation, and Zone 2 where it is unlikely and brief. Division 1 therefore spans what Zones 0 and 1 separate.
The luminaire standard reaches Zones 1 and 2 (gas groups IIA, IIB, IIB plus hydrogen and IIC) and Zones 20, 21 and 22, but not Zone 0. Zone equipment carries an AEx marking with its protection technique, gas group and temperature class.
The scope also limits the atmosphere itself: a minimum ambient of minus 60°C in the current text (minus 25°C in the 2019 text), oxygen no higher than 21 percent by volume, and a nominal pressure of one atmosphere. Oxygen-enriched or pressurised spaces fall outside it.
Temperature Codes (T-Codes)
The hottest surface of a luminaire must stay below the autoignition temperature of the gas or vapour present. The temperature code on the label states that maximum surface temperature at a 40°C ambient, unless the luminaire is marked for a higher ambient.
| Temperature code | Maximum surface temperature |
|---|---|
| T1 | 450°C |
| T2 / T2A / T2B / T2C / T2D | 300°C / 280°C / 260°C / 230°C / 215°C |
| T3 / T3A / T3B / T3C | 200°C / 180°C / 165°C / 160°C |
| T4 / T4A | 135°C / 120°C |
| T5 | 100°C |
| T6 | 85°C |
The sub-classes such as T2A and T4A exist only in the Article 500 Division system. Article 505 and the IEC 60079 series use T1 to T6 with the same limits.
A higher number means a cooler surface, so T6 is the most demanding. Acetylene ignites at 305°C, for example, so T2 is the minimum acceptable class there and any code from T2 to T6 will do.
Related Standards: UL 1203, UL 60079, CSA and ATEX
Several other documents cover the same hazards, and buyers often meet them in the same tender. The luminaire standard is one part of a wider family:
- UL 1203 (sixth edition, 2023): explosionproof and dust-ignition-proof electrical equipment in general, for Class I and Class II, Division 1, and the equivalent Zones.
- UL 60079 series: the US versions of the IEC 60079 standards, with US national differences, for equipment in Zones 0, 1, 2, 20, 21 and 22.
- CAN/CSA C22.2 No. 137-18: Electric luminaires for use in hazardous locations, the Canadian counterpart under the Canadian Electrical Code, Part I.
- ATEX, Directive 2014/34/EU: equipment for potentially explosive atmospheres placed on the EU market, with CE marking and notified body procedures.
- IECEx: the IEC system for certification to standards for equipment used in explosive atmospheres.
A listing under one scheme does not carry over to another. An ATEX or IECEx certificate is not a UL 844 listing, and a UL 844 listing does not by itself show compliance in Canada or the EU. A luminaire sold into several markets needs evidence for each.
Current Edition and Revision History
Check which revision a specification names, because a revision can change what an existing listing must meet. When the 2016 glass thickness requirements took effect on 28 April 2017, Intertek told clients that listings not meeting them would be suspended.
Specifying Lighting for a Classified Area
Most specification errors come from choosing the luminaire before the area is defined. Work in this order:
- Get the area classification document from the site owner or its engineer.
- Read the class and division, or the zone, and the group for each mounting position.
- Find the autoignition temperature of the materials present and choose a temperature code below it.
- State the ambient if it can exceed 40°C, because the rating must then be marked for that ambient.
- Ask for the listing certificate and check every item on the label against steps 1 to 4.
An ingress rating is not a hazardous location rating. It describes how well dust and water are kept out, not whether a fitting can ignite the atmosphere, so treat IP ratings as an extra requirement and never as a substitute.
Vehicles, Exit Signs and Lighting Near Hazardous Areas
The standard covers luminaires installed or used in classified locations; it is not a vehicle lighting standard. Lamps on tactical vehicles, such as military blackout lights, are specified to military documents like MIL-PRF-32212A.
Vehicles that carry dangerous goods by road follow their own electrical rules, set out in our guide to ADR compliance for vehicle lighting. ADR approves the vehicle, not individual lamps or fixed site lighting.
Non-electrical light sources avoid the ignition question altogether. Self-luminous tritium exit signs have no circuit, battery or lamp, so they bring no electrical ignition source into the area. Confirm their acceptance with the authority having jurisdiction, as for any sign.
Frequently Asked Questions
Yes, if it is installed in a classified location. LEDs run cooler than many lamps, but the driver and wiring are still electrical circuits and the housing still heats up. The scope covers fixed and portable luminaires without exempting any light source, and the temperature code must still sit below the autoignition temperature of the material present.
It covers suitability for the classified location, not emergency performance. Operation on emergency power is a separate evaluation under UL 924, Emergency Lighting and Power Equipment. A certificate for one does not imply the other, so an emergency fitting in a hazardous area needs evidence for both.
From UL Standards & Engagement, which sells the current thirteenth edition with its revisions through its standards shop. Public.Resource.Org hosts the text as revised in March 2019, but that predates the October 2021 revision, so use the current document for certification or design decisions.
The site owner or operator, usually through its engineers, not the lighting supplier. In the US, OSHA requires Zone areas, and Division areas designated after 13 August 2007, to be documented and available to those who design, install, inspect, maintain or operate equipment there (29 CFR 1910.307(b)).