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Fluids and Gases



Clearance Restrictions: Why They Matter —
and How to Avoid Them

Clearance restrictions apply when dealing with hazardous locations. The National Electric Code (NEC) defines a hazardous location as one where concentrations of flammable gas, vapors, or dusts can occur. This table defines the classification and location ratings applicable to users of Bruest catalytic heaters.

Summary of Class I Hazardous Locations
Classes Groups Divisions

I Gases, vapors, and liquids

(Art. 501)

A: Acetylene

B: Hydrogen

C: Ether, etc.

D: Hydrocarbons, fuels, solvents, etc.

1 2
Normally explosive and hazardous Not normally present in an explosive concentration, but may occur accidentally

Each classification has a minimal distance with respect to equipment that can be used near these locations. For instance, an outdoor natural gas receiving station could be classified as a Class I, Division 2, Group D location. The classified area would extend 15 feet in all directions from the potential leakage point (flange gaskets, valve seals, failure at meter, etc.).

This means any device not rated for operation in this environment must be installed at least 15 feet from the leakage point. In a second instance, if a relief valve is used in an outdoor natural gas drain tank, it could be rated as a Class 1 Division 1 Group D location, with the classified area extended 5 feet in all directions.

The use of non-rated equipment in a classified location means that a larger clearance area must be available. In the above example, a water bath natural gas heater, with a general wiring classification, must be installed 15 feet from the leakage point. Additional clearance may be required to service the heater, causing the total installation area to increase, and adding significantly to cost and operational concerns.

All Bruest catalytic heaters (including heater panels, area heat, Freez-Fiters, and HotCats) are rated for installation in Class 1 Div 2 locations. Bruest catalytic heaters can also be configured for installation in Class 1 Div 1 locations as an option.

Here is a video showing a Bruest catalytic heater in the presence of propane to demonstrate the safety of the heaters.

  • In this demonstration, a 12 inch Bruest catalytic heater is brought to full operational status. You can clearly see the catalytic pads glowing from the heat emitted from the catalytic reaction of the natural gas.
  • To demonstrate the presence of gas, a propane torch is applied without lighting the gas, sending the propane directly onto the heater surface.
  • The propane gas is simply catalyzed before it can ignite.

The ability of the Bruest catalytic heaters to be installed in locations classified as hazardous greatly reduces their installation cost. For more information, please contact our sales department at or 620-331-0750.