Mass removal of vapor phase gasoline, in pounds per visit.
PID concentration (ppm)*(4.49mg/m3*ppm)*(0.02832 m3/ft2)*flow rate (ft3/min)*operating time (minutes)*(1lbs/454,000mg)
WHERE: to mass concentration
PID concentration = photo-ionization detector read-out in parts per million (ppm);
4.49 mg/m3/1ppm = volumetric to mass concentration units conversion factor (Verschueren, 1983);
Flow Rate = Field readings in standard cubic feet per minute (SCFM);
Operation time = duration of pumping.