Hazardous Location Buying Guide

When working in environments with explosive dusts, gases, vapors, liquids, fibers, or flyings, ensuring safety is essential. In hazardous locations, selecting explosion-proof heaters and fans that are rated for your specific environment is critical for both safety and compliance. This guide will walk you through the key considerations for purchasing equipment designed to prevent ignition in hazardous environments.

Understanding Hazardous Location Classifications

The National Electric Code (NEC) has established a classification system that breaks hazardous locations into specific categories based on the type and presence of hazards. Selecting equipment that meets these standards is essential for safe operation.

Classifications Overview

Hazardous locations are categorized based on Class, Division, and Group:

• Class I: Locations where flammable gases or vapors are present, such as petroleum refineries, spray finishing areas, or oil rigs.
• Class II: Locations with combustible dust, including grain elevators, flour mills, food processing plants, and mines.
• Class III: Environments where ignitable fibers or flyings are present, such as textile mills and sawmills.

Divisions

The Division system indicates how often the hazardous materials are present:

• Division 1: Hazardous materials are present during normal operations, such as in paint spray booths.
• Division 2: Hazardous materials are present only during abnormal conditions, such as during equipment malfunctions or leaks.

Groups

The Group designation identifies the ignition properties of the materials present:

• Group A: Acetylene (Class I)
• Group B: Hydrogen and similar materials (Class I)
• Group C: Ethylene, cyclo-propane (Class I)
• Group D: Propane, gasoline, butane (Class I)
• Group E: Aluminum and magnesium dust (Class II)
• Group F: Carbon black, coal dust (Class II)
• Group G: Flour, grain, starch (Class II)

Key Design Features of Explosion-Proof Fans and Heaters

Explosion-proof fans and heaters are specifically engineered to prevent ignition in environments with explosive materials. Here are the critical design features you should look for when selecting equipment for hazardous locations:

Arcs and Sparks Containment

• The equipment is designed to contain any arcs or sparks that might be generated during operation, preventing them from interacting with flammable or explosive materials in the environment.

Temperature Control

• Explosion-proof heaters and fans operate below the ignition temperature of the hazardous materials present, ensuring that the system does not become a source of ignition.

Electrical Failure Prevention

• The equipment includes safeguards to prevent electrical failures that could create arcs, sparks, or high temperatures, further ensuring safe operation in hazardous conditions.

Explosion-Proof Equipment by Class

In Class I hazardous locations, the hazard is caused by the presence of flammable gases or vapors, and it is assumed flammable gases or vapors could seep into the equipment enclosure. The environment may also contain sparks and heat resulting from electrical failure.

Class I Features (Flammable Gases or Vapors)

• Strength: Designed to contain any internal explosions within the unit.
• Flame Paths: Designed to allow burning gases to cool before escaping, preventing external ignition. Flame paths may be designed to seal out dust and fibers while still allowing gases to escape, so many fans and heaters meet the requirements of Class I, II, and III.
• Ground surface flame path: Surfaces are ground and mated with 15 thousands of an inch clearance. This clearance allows gases to escape but only after they have been sufficiently cooled.
• Threaded flame path: Passageways to allow burning gases to cool and escape are designed into threaded joints.

Class II Feature (Combustible Dust)

In Class II hazardous locations, the hazard is caused by the presence of combustible dust. It is assumed that the environment may also contain sparks and heat resulting from electrical failure.

• Seals: Equipment must be sealed effectively to keep combustible dust out of critical components.
• Dust Buildup Accommodation: Equipment is designed to account for potential dust buildup without increasing operational risk.
• Sparks Containment: The design prevents the escape of sparks that could ignite dust particles.

Class III Features (Fibers or Flyings)

In Class III hazardous locations, the hazard is caused by the presence of easily-ignitable fibers or fillings. It is assumed that the environment may also contain sparks and heat resulting from electrical failure.

• Seals: Designed to prevent the infiltration of fibers and flyings.
• Operating Temperature: Maintains a safe operating temperature well below the ignition point of hazardous fibers.
• Fiber Buildup Accommodation: Equipment accounts for the buildup of fibers on surfaces without compromising safety.

System Design and Installation Considerations

Proper installation of explosion-proof heaters and fans is just as important as selecting the right equipment. In hazardous environments, special attention must be given to sealing power and control wiring conduit systems to prevent gases or flames from traveling through the conduits in the event of an explosion.

Important Note

This guide provides general information based on NEC standards. For specific hazardous location requirements, it’s essential to consult the National Electric Code (NEC) or work with a certified expert to ensure your installation is fully compliant.

Shop Explosion-Proof Fans and Heaters from NorthStock

At NorthStock, we specialize in providing HVAC professionals with a wide selection of explosion-proof fans and heaters designed for hazardous environments. Whether you're working in a chemical plant, refinery, or manufacturing facility, our products are built to meet the strict safety standards required for your industry.

For more information, browse our Explosion Proof Heaters and Hazardous Location Fans, or Contact Us for a quote today!