Fan Filter Units (FFUs) are becoming increasingly popular because of the flexibility they afford. Traditional central air handling units (AHU), used in combination with lay-in HEPA or ULPA filters, are becoming a thing of the past.

There are basically three components to an FFU: the motor, the housing, and the filter. Design improvements revolve around these three areas. Some motors, for example, are more efficient than others (Figure 1). Likewise, some housings are less expensive than others. Some filters are manufactured in ISO 9001 facilities; others are not. The most significant improvements, however, have come from the motor manufacturers.

The standard AC powered FFU allowed adjustment of its speed control for the fan (and hence the airflow) from either the top of the unit or from inside the cleanroom. Other option examples included a gel or gasket seal, HEPA or ULPA filters, particulate/chemical pre-filters, various voltages (115, 230, or 277V), aerosol dispersion mechanisms, and attached troffer lighting.

More recently, FFUs have taken an even greater cost conscious direction with the inclusion of built-in intelligence. These new “smart” FFUs offer a number of new benefits. First, they are powered by DC, which reduces energy consumption by as much as 50%. Second, their fan motors can be monitored and adjusted individually, in groups, or all at one time using a computerized control interface. By controlling the rpm of the fan motor and hence the airflow of the FFU, the operator has complete control over the systems at all times.