IGMA range of Heavy Duty Exhaust Fans are developed to combine high quality with being economically priced, economical to maintain and economical to operate.


IGMA Heavy Duty Exhaust Fans can be used in a wide variety of ventilation applications like power plants, warehouses, factories, parking garages, poultry farms or any general ventilation need.


IGMA Heavy Duty Exhaust Fans are of the propeller fan construction. The blade tip clearance is kept small and uniform to prevent air from flowing back around the propeller and thus achieving higher static pressure. The fans are designed to move large volumes of air at low static pressure but will perform well also at slightly elevated static pressure.


Fan Performance Airflow rate and static pressure are closely related for fans and ventilation systems. The airflow rate delivered by a fan is measured in cubic feet per minute (cfm) against a static pressure measured in inches of water. The amount of air moved is inversely rated to the static pressure. As the resistance to airflow (static pressure) increases, the delivered airflow capacity decreases. Therefore, a fan delivers more air against a lower static pressure than a higher static pressure. Common measurements used to describe the characteristics of a fan are blade diameter, revolutions per minute (rpm) and motor horsepower. These are useful measurements but without performance characteristics such as airflow and static pressure, they give only general indicators of fan capacity. Test results comparing the performance of 36-inch diameter fans used in the ventilation of enclosed buildings can show big variability in fan performance even though they are similar size fans. At a static pressure of 1/10 inch, the air delivery capacity of fans can easily vary from 6,400 to 10,000 cfm. These large variations in fan capacity for similar diameter fans significantly affects the selection process of fans. This shows the importance of selecting fans based on performance rather than strictly fan diameter or horsepower.

Energy Efficiencies

Exhaust Fan Performance Exhaust Fan Energy Efficiencies Another characteristic that is becoming important when selecting fans for ventilation system is energy efficiency. This is expressed as airflow per unit of input energy, or cfm per watt. The higher cfm per watt rating will indicate a more efficient fan. Tests on 36-inch diameter blade fans indicate a wide variation in both fan performance (6,400 to 13,000 cfm) and energy efficiencies (8.3 to 18.6 cfm per watt) at 1/10 inch static pressure. Even fans with similar airflow ratings can have a significantly different energy efficiencies. On 36-inch diameter blade fans yielding airflow ratings between 9,000 and 9,900 cfm at 1/10 inch static pressure, the energy efficiencies, as measured in cfm per watt, can vary from 8.4 to 18.6 cfm per watt. The electrical energy cost of these two extremes based on an airflow rating at 1/10 inch static pressure with an electrical rate DHS0.20 per kilowatt hour and 365 days (24 hrs per day) of operation for a warm-weather fan, shows a cost savings of nearly DHS945 per year (DHS1877 compared to DHS933) by using the more energy efficient fan.

Exhaust Fan Dimensioning

Typical Minutes per Air Change:

Boiler Room
Machine Shop
Summer Cooling
Welding Shop
General office

To determine the proper IGMA Heavy Duty Exhaust Fan for your applications, use the following formula.

Number of cubic feet in room / Number of minutes per air change = Required C.F.M. Capacity


A general office, (see chart) which requires an air change every ten minutes, would require the following fan capacity. If office is 100’ x 40’ x 10’ = 40,000 cubic feet

40,000 cubic feet / 10 minutes per air change = 4000 Required C.F.M.

You would select a fan that is rated at 4000 C.F.M. at 1/8” S.P. (Static Pressure). The total static pressure the fan must overcome is the sum of the individual resistances. Typical resistances to air movement.

Type of resistance
Data Total static pressure in "
Properly sized and managed inlet
Exhausting against wind
Exhausting agains wind
Exhausting agains wind
Exhausting against wind
Fan guards
Clean wire mesh
Fan guards
Round ring

Guards typically reduce airflow and efficiency by less than five percent. Guards are essential for the safe operation of the fan. Guards also protect the fan from being damaged by large objects that can strike the blades. All fans can be mounted horizontally as well as vertically. If the air flow direction is set towards the motor then the performance will be reduced by approximately 10% compared to the specification.