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Class 1 Div 2 Lighting | UL Certified Models (2026) | ISS
Facilities use Class 1 Division 2 lighting where a fire or explosion hazard may exist due to flammable liquids or gases being used or stored there. The standard UL 844 and the National Electric Code (NEC) article 501 govern the construction of lighting fixtures to provide confidence in the safe operation in hazardous classified environments.
The National Electrical Code (NEC), National Fire Protection Association (NFPA), and Underwriters Laboratories (UL) published a guide along with codes that categorize hazardous areas into classes, divisions, and zones.
Class 1 hazardous locations refer to facilities that deal with flammable gases, vapors, and liquids.
Division 2 indicates that the facility handles, processes, or uses flammable material at the location. However, the material isn’t constantly circulating in high enough concentrations to be ignitable. Simply put, this requires proper handling and storage of flammable gases, vapors, or liquids to prevent ignition under standard operation. Additionally, the facility might utilize a positive-mechanical ventilation system that prevents high concentrations from forming. As a result, the presence of flammable gases or liquid-produced vapors will never reach an ignitable level.
Division 2 has four group subdivisions, defining the different types of hazardous materials present at a location.
The following signify the groups of hazardous substances that may be present at a location.
A – contains only acetylene.
B – includes hydrogen, gases with more than 30% hydrogen by volume, butadiene, ethylene oxide and propylene oxide.
C – includes acetaldehyde, cyclopropane, diethyl ether, and dimethyl hydrazine.
D – includes gasoline, acetone, ammonia, benzene, butane, methane, propane, alcohols and other more commonly encountered compounds.
Temperature Class: The Rating That Determines Which Lighting Is Safe to Install
Beyond the Class, Division, and Group markings, a Class I Division 2 lighting fixture also carries a temperature class (T-rating), such as T3, T4, or T5. This rating states the maximum surface temperature the fixture can reach under both normal operation and single-fault conditions, per NEC Article 500 and UL 844. That maximum surface temperature must stay below the autoignition temperature of the specific gas or vapor present at the site — for example, gasoline vapor has a lower autoignition point than methane, so a facility handling gasoline requires a lower (more conservative) T-rating than one handling methane alone. Matching the T-rating to the actual substances on site is part of the facility’s hazardous area classification study, typically documented alongside the Class/Division/Group assessment.
What to Look for in a Class I Division 2 Light Fixture
Beyond the base UL 844 / NEC 501 certification, several practical factors distinguish one Division 2 fixture from another:
- Light source: Most current Division 2 fixtures use LED arrays rather than older fluorescent or HID sources, which reduces both heat output (relevant to the T-rating above) and maintenance frequency.
- Mounting configuration: Common formats include linear fixtures for continuous runs along ceilings or walkways, flood lights for wide-area illumination of yards or process areas, and pendant or flange-mount fixtures for fixed-point lighting near equipment.
- Ingress protection (IP) rating: A separate rating from the hazardous-location certification, IP66 or higher is standard for fixtures exposed to washdown, dust, or outdoor weather.
- Voltage range: Many industrial sites specify fixtures with a wide input voltage range (e.g., 100–277V or 347–480V) to match existing electrical infrastructure without a separate transformer.
Reading a Division 2 Fixture’s Certification Marking
A compliant fixture’s nameplate will list its classification in a standardized format, for example: Class I, Division 2, Groups A, B, C, D; T4. This states the Class (I — gases/vapors), the Division (2 — hazard present only under abnormal conditions), every Group the fixture is rated for, and the temperature class. A facility’s own hazardous area classification documentation should specify which of these the installed equipment needs to match; installing a fixture rated for fewer Groups than the site requires is a common compliance gap identified during electrical inspections.
Where Class I Division 2 Lighting Is Typically Installed
Division 2 areas are common in oil and gas facilities (outside the immediate wellhead or tank vent), chemical processing plants, parts washing and solvent storage areas, and warehouses storing flammable liquids in closed containers. Because the hazard in these areas exists only under abnormal conditions — a spill, a leak, or equipment failure — Division 2 fixtures see wide use anywhere flammable material is present but normally contained.
FAQs About Class I Division 2 Lighting
What’s the difference between Division 1 and Division 2 lighting?
Per NEC Article 500, Division 1 covers locations where ignitable concentrations of flammable gases or vapors can exist under normal operating conditions, while Division 2 covers locations where they are present only under abnormal conditions, such as equipment failure or a containment breach. Division 1 fixtures are built to a more stringent standard and are typically heavier and more expensive as a result.
Can a Division 1 fixture be used in a Division 2 location?
Yes — a fixture certified for the more demanding Division 1 rating meets the requirements for Division 2 as well, since Division 1 encompasses the conditions covered by Division 2. The reverse is not true.
Do Class I Division 2 fixtures require special installation procedures?
Installation must follow NEC Article 501 and the site’s hazardous area classification documentation, typically carried out by a licensed electrician familiar with hazardous location wiring methods (e.g., sealed conduit fittings where required).