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Guide to Explosion Proof Lighting Classification
Explosion proof lighting requirements are defined by the Occupational Safety and Health Administration (OSHA). This type of lighting is required for hazardous locations. This includes:
- Areas that contain flammable vapors, liquids, or gases
- Areas that contain combustible dust or fibers
We woudn’t be very surprised to know that you never much thought about the factors like personal and property security while purchasing lighting solution for your commercial or industrial facility. However, take our word of caution here.
As the owner of a facility, you must know the potential hazards related to lighting that can occur with using the wrong type of lights. There are many hazardous places in the US that need to use Hazardous Location lighting.
- Storage areas
- Grain elevators
- Gas stations
- Chemical plants
- Food processing plants
- Waste treatment facilities
- Power generation
- Paint shops
Why is LED a Must for Hazardous Locations?
Hazardous Location Risk factors
As the manager or owner of any facility where activities in hazardous environments are performed every day, you must know that you are putting everyone working in your facility at risk by not having the right hazard-safe lighting installed on the premises.
If you use the wrong lights that do not comply with the classification standards of hazardous locations, then you could be charged in violation of the regulatory standards of OSHA, NFPA, and NEC/CEC. Even small-scale accidents can result in large penalties.
How do locations identify as being hazardous?
Determing a hazardous location depends on many of factors. You can identify a location as hazardous based on whether a particular type or amount of fuel is stored, or explosive dust is present.
Presence of Flammable Liquids and Gases
Wherever flammable gases and liquids are present, the location may be identified as a hazardous one because such compounds can cause an explosion or catch fire.
Gas and liquids must achieve a critical concentration before it becomes dangerous. However, once they do, that’s when a potential disaster can occur.
How do high concentrations create hazardous conditions?
The 2005 Texas Refinery case is an example of a gas explosion where the incident was started by the huge accumulation of hydrocarbons in the air that leaked accidentally and was vaporized.
The concentrated gas cloud was ignited by the hot exhaust of a vehicle parked on the premise.
Many other flammable gases can cause this like ethylene, hydrogen, ammonia, methane, butane, carbon monoxide, propane, acetylene, and many others.
Presence of Air-Suspended Combustibles, Fibers/Dust
Have you ever thought about dust being dangerous? Well, if not then you should know that there are many flying fibers including dust that can turn out to be hazardous.
Dust can be harmful in two ways.
Formation of an explosive cloud by mixing with air and overheating electrical components by accumulating on their surface and insulating their heat.
In wall, electrical fires can be caused by dust fibers.
Between 2008 and 2012, 29 causalities and more than 160 people were injured due to combustible dust explosions.
Four Industrial Sectors that may generate harmful explosive / combustible dust
Agricultural products including spices, grass, cotton, coffee, grains, dust, flour, wood flour, sugars, starches, powdered milk, egg white, and other agricultural dust
Industrial products that form carbonaceous clouds including cellulose, cork, petroleum coke, charcoal, coal
Chemical products including sulfur, lactose, methyl-cellulose, and metal dust including zinc, magnesium, aluminum
Different plastic products including vinyl varieties, melamine
Methods of Stopping Ignition
Even though dust, liquids, and gases differ a lot from each other in almost all aspects, the one thing that they have in common is their trigger point or ignition. If they don’t ignite, there is no issue. So, how does ignition occur?
The ways fuel ignites is – the fuel is in an explosive state and is exposed to an ignition source like an open flame, spark, and air in combination or the fuel reaching its Auto Ignition temperature (AIT).
AIT is the point when fuel ignites in the absence of any external ignition source. AIT scores are used by safety organizations to decide the maximum operating temperature standards for heat-emitting devices like heavy machines, etc.
HAZLOC safe LED lights are built as per the safety standards to contain flames or sparks during any general or emergency operating situation. These lights are also built according to the maximum operating temperature standards that are set to match the individual settings of the lights. The reason why LEDs are best for this task is that they are initially built to operate at very low temperatures, making them the safer option.
Classification of Hazardous Locations and Devices
To ensure proper and safe lighting in the areas that remain vulnerable to hazardous accidents, the National Electric Code or NEC has set standards that classify the various risk levels meant for lighting to be approved as HAZLOC safe. This is meant to help you identify the right light for your location if it lies in the hazardous category.
The hazardous areas have been classified by the NEC based on groups, classes, divisions, and sectors. You can check the categorical identity of your area from the table on the right .
The following are the first three classifications identified by the NEC on a broad environmental basis:
Class I – These areas have flammable vapors or gases with topmost concentrations that can ignite when encountering electric sparks or open flames instantly.
Class II – These areas have a concentration of combustible dust.
Class III – These areas have a concentration of ignitable fires.
These classification groups have been further divided by the NEC into three subsets that are based on specific factory regulations. The further two divisions have the hazardous lighting locations being grouped into the sets based on their level of exposure to the dangerous materials.
Division 1 – The ignitable substances remain in the surroundings all the time, periodically during regular times, or releases during any maintenance activity or machine failure.
Division 2 – The ignitable substances remain present but in a controlled concentration due to proper ventilation and other release methods.
Those are the NEC classifications. You may have noticed that these classifications are more about the light location.
The next classification standards set by The Occupational Safety and Health Administrations or OSHA are for the categorization of lights based on their characteristics, model, and material concentrations.
The classes are denoted with letters from A-G:
Class I gases – Start with letters A-D. The gases of Group A possess the highest explosion pressure such as Acetylene and the gases of Group D have the lowest pressure such as propane.
Class II gases – Start with letters E-G. Group E has metal conducive dust such as magnesium, Group F has carbonaceous dust like coal, and Group G has non-conducive dust such as plastic, wood, and grain.
What does Explosion Proof lighting mean?
OSHA requires certified explosion proof lights in hazardous areas that contain flammable vapors, gases, liquids or combustible dust or fibers. Luminaires that meet the explosion-proof lighting standard are built to contain any internal explosion inside the fixture, so no exploded material leaves the fixture.
Thus, containment is the main idea behind the design of these lights. The hard glass and metal walls of these fixtures make them highly sturdy.
Explosion proof lights must have all the tests and certifications done as per the set standards and safety measures. Class 1 Division 1 and Class 2 Division 2 are the most general standards.
These classes are divided primarily based on the presence of flammable substances in the surroundings of the light. In the first group, substances like vapors, gases, and other materials are present all the time.
In the second group, the substances like vapors, gases, and other materials are not present all the time.
What Does Intrinsically Safe Lighting Mean?
These lights are much like explosion proof lights.
However, the main difference is that while explosion proof lights are meant to contain the explosion happening inside its fixture, intrinsically safe lights are fixtures that are built with wiring or electronics that prevents those conditions inside a fixture that can result in an explosion. In other words, they can’t build up enough energy that could possibly ignite gas or vapor.
Thus, intrinsically safe lights are explosion-incapable lights. This also means that they are not meant to contain any explosion inside their fixture.
These lights can be low power or low voltage but that’s not always the case. However, a low power or low voltage intrinsically safe light is easier to manufacture than its high standard counterpart.
This is the reason that most high-power LED lights are explosion proof and not intrinsically safe. You may also see battery-operated intrinsically safe lights.
What Does Vapor Proof Lighting Mean?
Vapor proof lights have very tight seals meant to protect from an intrusion of its interior by an element from the exterior environment. These lights keep substances like dust, vapor, gases, particles, moisture and water from damaging the internal components of the fixture.
Does Vapor Proof Mean Explosion Proof Too?
No. Vapor proof lights are designed to resist the entrance of any gaseous, vaporous, or other material inside. They can neither prevent explosions nor contain them at any time.
Does Explosion-Proof Mean Vapor Proof Too?
That can be the case but not always. Explosion proof lights are not specifically built to prevent the entrance of external elements like materials, gases, and vapors, etc.
However, what these lights certainly do is prevent or contain explosions just in case. Thus, you cannot expect the explosion proof lights to be vapor proof too.
About the Author
Neil Peterson is Chief Operating Officer at LED Lighting Supply. He has been active in the LED industry for over 10 years and is responsible for product planning and management as well as revenue and operations at LED Lighting Supply. Much of Neil’s time is focused on customer engagement for large commercial and industrial lighting requirements. When not working, he enjoys family time, camping, fishing, and sports..