Benefits of Indirect Fired Heaters

Fired heaters do just as the name implies: generate heat via the use of combustible materials. In direct fired heaters, air is forced across an open flame. In an indirect fired heater the flame is contained in a special burner, which warms up a heat exchanger. Air is then forced across that exchanger to heat up the area.

Some models of direct fired heaters are less expensive than their indirect counterparts and don’t require electricity, but since direct heat over an open flame can add carbon monoxide to the air, their use is limited typically to larger, well-ventilated spaces like warehouses or open construction areas.

Deciding whether to use an indirect fired or direct fired unit will depend on the intended use, but indirect fired heaters certainly have benefits.

 Safer air

Carbon monoxide poisoning kills workers every year. Victims are usually using fuel-burning equipment in spaces without adequate ventilation, according to the Occupational Safety and Health Administration. Indirect fired heaters do not produce carbon monoxide, carbon dioxide or nitrogen dioxide, so they are safe to use in tight spaces, although they still need an exhaust outlet. In addition, since the air is emissions free, operators can use duct systems to transfer warm air from an indirect fired unit to other nearby spaces.

Drier air

Indirect fired heaters deliver cleaner air with less humidity. Excess humidity can create drying and curing problems during some operations and lead to mold development in extreme cases. Indirect fired heaters can actually help some wintertime processes, like the curing of concrete, along.

Fuel savings

Direct fired heaters may be more fuel efficient overall, but since indirect fired heaters do not have the fresh air requirements of direct fired heaters, they can save fuel when used in recirculation mode or to warm nearby spaces.


Kim Slowey is a writer who has been active in the construction industry for 25 years and is licensed as a certified general contractor in Florida. She received her BA in Mass Communications/Journalism from the University of South Florida and has experience in both commercial and residential construction.