HI-Q Environmental Products Company`s steel constructed, two-component polyurethane painted Air Flow Calibrator (AFC) housings incorporate a precision machined venturi tube to create a pressure differential across a fixed orifice. By varying the air flow velocities, the pressure differentials are measured & recorded against a laminar flow element whose calibration is certified and traceable to the National Institute of Standards and Technology (N.I.S.T.). The AFC`s overall internal simplicity of operation reduces the frequency of re-calibration to once or twice per year depending on (individual) regulatory protocol. AFC-XX series air flow calibrators are intended to be used open to air.