Direct-Fired Systems

DFM: Direct Fired Indoor Mounted · DFC: Direct Fired Curb Mounted · DFL: Commercial Direct Fired Make Up Air

Flexible units for space heating, make-up air, and ventilation applications

100% Efficient Gas Burner

Gas Burner Section

Factory set and tested to ETL standards for 100% efficiency.

Gas Manifold

Gas Manifold

Completely factory assembled and tested.

Optional Intake Hood

Optional Intake Hood

For outdoor models (DFC, DFL), Applied Air offers a complete matching intake hood.

Particulate Air Filter


Optional filter module keeps out bugs and helps minimize accumulation of dust, dirt, and airborne particles in the space.

Access Doors

Access Doors

Full size doors provide easy access to fan, burner, and controls. Access doors are hinged and use industrial grade fasteners.

AMCA Tested Centrifugal Blowers


Direct Fired units feature centrifugal blowers tested to AMCA standards and motors with adjustable bases.

When more air is exhausted from a building than is supplied by the mechanical systems, the building is under a "negative" condition and air will leak into the building through cracks, windows and doors. A negative condition results in the following:

Direct-Fired System Breakdown

Direct Firing eliminates the need for heat exchangers, resulting in 100% efficiency. All products of combustion are introduced into the supply air stream at concentrations well below code requirements. As natural gas is an abundant, clean and low cost fuel that is readily available, this system is very cost effective to operate.

How Direct Fired Gas Heating Works

Direct Fired gas heating is one of the simplest and most cost-effective methods for heating air. Outside air enters the unit (at point C) and is either filtered or not. If desired, a quantity of returning room air can be added (B) to this outside air in a balanced fashion to assure a constant total airflow. This air then passes over a line burner: The airflow pattern is closely controlled using profile plates, resulting in 100% efficient combustion.

Direct Fired Gas Heating Diagram

The air is directly heated by this clean, controlled gas flame and distributed into the building using heavy duty centrifugal blowers (G). By carefully controlling the airflow pattern and volume, the system can provide complete, 100% combustion. Complete combustion produces only water vapor and carbon dioxide (CO2). Harmful combustion by-products are the result of incomplete combustion and a good reason why you should buy from an established expert in gas heating technology.

Features and Benefits of Direct Fired Gas Heating

Direct Fired Heating

Heats Without Complications

The Direct Fired gas heating system heats efficiently and cost-effectively using no heat exchanger.

Replaces Indoor Air

The Direct Fired gas heating system replaces indoor air that can become chemical laden in an industrial process or commercial cooling application.

Provides Ventilation

Fresh air is available simply by turning off the heating section.

Air Delivery for Small or Large Buildings

With fans tested to AMCA standards for airflow from 1,600 to 100,000 CFM, you can put warm air right where you need it.

Improves Comfort Anywhere, Anytime

Add cost-effective evaporative cooling to your Direct Fired gas heating system for year-round comfort.

Cleans and Tempers Incoming Air

The optional filter bank removes airborne particles, and cleaned air is heated to create a more refreshing and comfortable indoor environment.