=+4-26.

Using M-15 filter media and the requirement of 60 cfm per person of outdoor air for the case of a designated smoking area for 55 persons, design a filter and air-circulation system allow.

ing the actual outdoor air rate to be reduced to 20 cfm per person. Assume outdoor and recir-

culated air are mixed before filtering and insignificant amounts of outdoor air contaminants are present. The filter media must have a gravimetric efficiency of 80 percent in the 0-5 x 10~1 mm particle size range. The filter pressure loss should not exceed 0.12 in. wg.