Don’t be afraid to monitor particle counts and control airflow. Old-school thinking was “don’t ever mess with airflow, even by the slightest amount, because the sky will fall and product yield will drop. Therefore, active particle monitoring is unnecessary.” Modern thinking is that the room conditions change over a day, week, or month.

Even the number of occupants (particle generators) will vary; therefore the particle load will vary. Why not vary the airflow to match the load? The particle count is the goal, not an airflow amount.

Firmly established quality protocols enable the reduction of cleanroom airflow without compromising product quality. Centralized air handling units, using efficient fans with variable-frequency drives, can be installed in lieu of less efficient fractional-horsepower fan filter units located throughout a typical 2’x4′ ceiling grid fully populated with ULPA filters. The central fans are controlled automatically through a computerized Building Management System (BMS).

From: Ask the Facilities Guy