Duct Air Heaters

Direct Fired Duct Air Heaters

Our industrial direct gas-fired duct air heaters are completely packaged with air heat burners and controls. Designed to fit into the processes’ duct work, these process air heaters offer the utmost in customer convenience with prewired and prepiped assembly.

Duct-style fired air heaters are used independently or in conjunction with dryers, kilns, ovens, furnaces and other heat equipment. Applications include baking, curing, heat treating, printing and many more.

Stelter & Brinck duct air heaters are available in fresh air duct section, recirculating duct section, and selective catalytic reduction models. A low-emissions option is available for each of our industrial duct air heater models.

Stelter & Brinck industrial duct air heaters are designed to be easy to use and install, among the features offered are:

  • Control panel with flame safety relay, first out annunciator, relays and breakers, alarm horn, local start/stop push buttons, illuminated “E” stop button, indicator lights, FM approved high temperature limit, and PID digital temperature controller (single or multi-loop). UL 508A priced per request.
  • Remote control interface capability for use with PLC or DCS systems available.
  • Built to meet your requirement (FM, CE, GAP, NFPA or or CSA construction standard).

Stelter & Brinck duct heaters are designed to provide unmatched performance in direct fired air heating. Our duct heaters are a product of more than 95 years of industrial combustion equipment experience and feature:

  • High energy turndown
  • Fully proportional temperature control valve
  • Fires on natural, propane, or butane gasses. Other fuel options available upon request.
  • Rigorously tested and tuned before shipment
  • Easy maintenance, easy access to all parts
  • Stelter & Brinck’s combustion field service crew can start-up and maintain your direct fired air heater


AHD Style Process Air Heaters are designed to be inserted right into your process ductwork. The burner in our AHD units uses the oxygen present in the process stream for combustion eliminating the need for an additional combustion air source.

As the name suggests, our Fresh Air Duct Heater is suitable for use on clean air streams. Our AHD features:

  • Steel liner, insulated & covered with steel skinning
  • Flame peep sight
  • Packaged fuel control and safety valve train
  • Single point fuel connection
  • Prewired to numbered terminal strip


AHDR Air Heaters are designed to be inserted right into your process ductwork. The direct-fired, recirculating duct air units are designed for recirculating industrial process air streams with low oxygen content and feature a combustion blower.

High and low inlet and outlet temperatures are acceptable. The AHDR features:

  • Combustion air inlet
  • Fully insulated, heavy steel construction
  • High turndown burner
  • Prepiped and prewired fuel valve train
  • Packaged fuel control & safety valve train
  • Single point fuel connection



Selective Catalytic Reduction (SCR) Air Heaters are low NOx, direct fired systems which can be designed to be either a start-up air heater or a post-heater (reheater). SCR Air Heaters are typically used in conjunction with utility boilers, tail-end SCR configurations, and with any other system where nitrogen oxides (NOx) are present, but the flue gas temperature is below the range required for the SCR catalyst reaction.

SCR start-up air heaters prevent low temperature corrosion during boiler start-up.

SCR Air Reheaters can also be referred to as Flue Gas Heaters or SCR Duct Burners.

  • Can use the oxygen present in the flue gas or a separate combustion air source, if there is not enough oxygen present in the stream.
  • Provide consistent and reliable performance in tough conditions.
  • Fully packaged, pre-piped and prewired.
  • Like all S&B equipment, our SCR Air Heaters are tested fired and tuned before shipment in our factory.