=+4-25.

Work Problem 4-24 but replace the 100 percent outdoor air requirement with 25 percent out-

door air and use high-performance filters for the return air. Gravimetric efficiency must be at least 99 percent in the 0-5 x 10-6 meter particle range.

(a) Find the required air flow and

(b) design the filter system so that the maximum pressure loss with clean filters is less than 0.125 in. wg.