Heavy duty construction. The filter housing anodized non-corrosive flaking aluminum. These modules are designed to receive air from your HVAC system (check with Liberty for CFM and static requirements). This module comes with a 10" duct collar on top. Filter modules mount in standard T-bar ceiling. Units operate with recirculating air through a return wall plenum or through a 30% NBS efficient prefilter using air from ambient or exterior of cleanroom. Either condition can deliver better than Class 100 (ISO 5) clean air. 2' x 4' HEPA filter is 99.99% efficient on particles of 0.3 micron and larger .(optional 99.999 % at 0.12 micron.)