Understanding Hazardous Area Classifications
Anywhere gas, flammable vapors, combustible dust, fibers, or flyings are present is considered a hazardous location. These locations can range from airplane hangars, gas plants, and dry cleaning facilities to mines, granaries, and textile mills. Substances in these areas have the potential to cause explosions if they’re around the wrong electrical equipment. It takes just one blown bulb or spark to ignite an entire area. Each piece of electrical equipment or lighting that’s used in a hazardous location must meet requirements for the type of environment it will be used in. It’s important to understand this hazardous area classification system so that you can make a safe, informed decision when it comes to adding hazardous location lighting.
The National Fire Protection Association (NFPA), National Electric Code (NEC) 70, defines hazardous locations through a system of classes, divisions or zones, and groups that products must be labeled as to be used in those areas. Hazardous area classifications are based on the general type of substance or material that is present in the area, the likelihood that it exists, and more detailed specifics, such as ignition temperatures and combustible properties.
Classes: Type of substances or materials
Class I:
A Class I hazardous location contains flammable gas, liquid-produced vapors, or combustible liquid-produced vapors that can be present in quantities large enough to create an explosion.
Typical locations include airplane hangars, vehicle paint shops, commercial laundromats, and gas plants.
Class II:
This class consists of combustible dust that is present in hazardous quantities.
Typical locations include granaries, mines, sugar or starch plants, and plastic-producing factories.
Class III:
This type of location contains easily ignitable fibers or flyings in the air but that aren’t likely to be in suspension in amounts large enough to cause an explosion.
Typical locations include textile mills, cotton mills, and sawmill facilities.
Divisions: Likelihood that substances or materials exist
Division 1:
The substance or material exists or is likely to exist under normal conditions or may exist frequently due to repair, maintenance, leakage, equipment breakdown, or faulty operation.
Division 2:
A substance or material doesn’t normally exist in the area or is confined in closed containers where it escapes only in the case of an accidental rupture, breakdown, or abnormal equipment operation.
Class I, Division 1:
A Class 1, Division 1 location contains flammable gas, liquid-produced vapors, or combustible liquid-produced vapors that can be present in quantities large enough to create an explosion. The substance exists or is likely to exist under normal conditions or may exist frequently due to repair, maintenance, leakage, equipment breakdown, or faulty operation.
Class I, Division 2:
In a Class 1, Division 2 location, flammable gas, liquid-produced vapors, or combustible liquid-produced vapors are not likely to exist normally. Substances are confined in closed containers where they escape only in the case of an accidental rupture, breakdown, or abnormal equipment or ventilation operation. This classification can also be given if an area is located adjacent to a Class I, Division 1 location and doesn’t have proper pressure ventilation.
Class II, Division 1:
A Class 2, Division 1 location consists of combustible dust that is present in hazardous quantities. The substance exists or is likely to exist under normal conditions or can be produced by equipment breakdown or faulty operation. This classification can also be given if hazardous quantities of Group E combustible dusts exist in the area.
Class II, Division 2:
In a Class 2, Division 2 location, hazardous quantities of combustible dust may exist because of abnormal operations and could accumulate on electrical equipment—preventing proper heat dissipation. Combustible dust in these areas could also be ignited by abnormal equipment operation or equipment failure.
Class III, Division 1:
In a Class 3, Division 1 location, easily ignitable fibers or combustible flyings are made, handled, or used. These materials aren’t likely to be in suspension in amounts large enough to cause an explosion.
Class III, Division 2:
In Class 3, Division 2 locations, easily ignitable fibers or combustible flyings are stored or handled but aren’t manufactured.
Zones: Likelihood that substances exist
Zone 0:
Hazardous amounts of flammable gas or vapor exist continuously or for long periods of time.
Zone 1:
Flammable gas or vapor is likely to exist during normal operation or may exist frequently due to repair, maintenance, leakage, equipment breakdown, or faulty operation. This classification can also be given if an area is located adjacent to Zone 0 and doesn’t have proper pressure ventilation.
Zone 2:
Gas is not likely to exist normally but can occur for short periods of time. Flammable liquids, gas, or vapors are confined in closed containers where they escape only in the case of an accidental rupture, breakdown, or abnormal equipment or ventilation operation. This classification can also be given if an area is located adjacent to Zone 1 and doesn’t have proper pressure ventilation.
Zone 20:
Combustible dust or ignitable fibers/flyings exist continuously or for long periods of time.
Zone 21:
Combustible dust or ignitable fibers/flyings are likely to exist during normal operation or may exist frequently due to repair, maintenance, leakage, equipment breakdown, or faulty operation. This classification can also be given if an area is located adjacent to Zone 20 where materials could come in contact with one another.
Zone 22:
Combustible dust or ignitable fibers/flyings are not likely to exist normally but can occur for short periods of time. Materials are confined in closed containers where they escape only in the case of an accidental rupture, breakdown, or abnormal equipment or ventilation operation. This classification can also be given if an area is located adjacent to Zone 1 and doesn’t have proper pressure ventilation.
Class I, Zone 0:
In Class 1, Zone 0 locations, hazardous amounts of flammable gas or vapor exist continuously or for long periods of time.
Class I, Zone 1:
In Class 1, Zone 1 locations, flammable gas, liquid-produced vapor, or combustible liquid-produced vapor is likely to exist during normal operation or may exist frequently due to repair, maintenance, leakage, equipment breakdown, or faulty operation. This classification can also be given if an area is located adjacent to Class I, Zone 0 where materials could come in contact with one another.
Class I, Zone 2:
In Class 1, Zone 2 locations, flammable gas, liquid-produced vapor, or combustible liquid-produced vapor is not likely to exist normally but can occur for short periods of time. Liquids, gases, and vapors are confined in closed containers where they escape only in the case of an accidental rupture, breakdown, or abnormal equipment or ventilation operation. This classification can also be given if an area is located adjacent to Class I, Zone 1 and doesn’t have proper pressure ventilation.
Groups: Ignitable/Combustible Properties
Class I groups: according to NEC 500.6 (A)(1)-(A)(4):
A: Acetylene 497:3.3.5.1.1
B: Flammable gas, flammable liquid-produced vapor or combustible liquid-produced vapor mixed with air that may burn or explode, having either a maximum experimental safe gap (MESG) value less than or equal to 0.45mm or minimum igniting current (MIC) ratio less than or equal to 0.40.
Typical: Hydrogen 497:3.3.5.1.2.
C: Flammable gas, flammable liquid-produced vapor or combustible liquid-produced vapor mixed with air that may burn or explode, having either a maximum experimental safe gap (MESG) value greater than or equal to 0.45mm or less than 0.75mm, or minimum igniting current (MIC) ratio greater than 0.40 and less than or equal to 0.80.
Typical: Ethylene 497:3.3.5.1.3.
D: Flammable gas, flammable liquid-produced vapor or combustible liquid-produced vapor mixed with air that may burn or explode, having either a maximum experimental safe gap (MESG) value greater than or equal to 0.75mm or minimum igniting current (MIC) ratio greater than 0.80.
Typical: Propane 497:3.3.5.1.4.
Class II groups: according to NEC 500.6 (B)(1)-(B)(3):
E: Atmospheres containing combustible metal dusts, including aluminum, magnesium and their commercial alloys, or other combustible dusts whose particle size, abrasiveness and conductivity present similar hazards in the use of electrical equipment.
Typical: metal dusts 499:3.3.4.1.
F: Atmospheres containing combustible carbonaceous dusts that have more than 8% total entrapped volatiles (based on ASTM D3175-11) or that have been sensitized by other materials so that they present an explosion hazard.
Typical: Carbonaceous dusts, such as coal, carbon black, charcoal, and coke dusts 499:3.3.4.2.
We offer several explosion-proof LED lights that are safe for use in a variety of hazardous locations. Click each photo to see details, including a complete list of classifications and certifications.
If you have any questions, don’t hesitate to call us toll free at 866-590-3533. Our customer service and technical support teams are available from 8:30 a.m. to 8 p.m. CDT Monday-Thursday and 8:30 a.m. to 4 p.m. CDT on Friday.
