\ v Hart&Cooley. SUBMITTER DRAWING install confidence POLYETHYLENE VAPOR BARRIER FIBERGLASS INSULATION CORE WIRE HELIX CORE Two plies of black polyester film encapsulate a steel wire helix. *Rated pressures (UL—181): 12 in. W.C. positive, 3/4 in. W.C. negative & 1/2" W.C. negative (>1279). «Recommended maximum operating pressures (ADC Test FD 72-Rio: 6 in. W.C. positive for 12 in. diameter and under. 4 In. W.C. positive for 14 in. diameter and over. «Rated maximum air velocity: 5000 FPM.