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The standards are produced by infecting measured volumes of known <br /> density gasoline or BTEX compounds into tedlar bags filled with a <br /> measured amount of air, usually one liter. The gasoline standard is <br /> made by infecting 10 microliters (µl) of 0 75 mg/µl gasoline into <br /> one liter of air, the density was previously determined by weighing <br /> a know volume of gasoline The resulting concentration is 10 pl x <br /> 0 75 mg/pl / 11 = 7 5 mg/l The BTEX standard is made by inDecting <br /> 5 Al of each compound into one liter of air, and using the following <br /> densities to calculate the concentration Benzene, 0 88 mg/µl , <br /> Toluene, 0 87 mg/µl , Ethylbenzene, 0 87 mg/µl , Xylenes, 0 . 87 mg/µl . <br /> The following are the resulting concentrations - Benzene, 4 4 mg/l , <br /> Toluene, 4 35 mg/l , Ethylbenzene, 4 35 mg/1 , and Xylenes 4 . 35 mg/1 <br /> FLOW RATES <br /> Flow rates are measured at the site using an orifice plate A one <br /> inch orifice-sampling manifold is placed directly on the casing <br /> of the monitor well, carefully avoiding any vacuum leaks An <br /> orifice plate restricts the flow causing a pressure drop across <br /> the orifice By measuring the resulting pressure change across <br /> the orifice it is possible to calculate the air flow rate . The <br /> flow rate is calculated by the pressure drop (millimeters (mm) <br /> mercury or water) across a square edge orifice plate <br /> Ve = CK sgr(P) Q = AVe <br /> Where <br /> Ve= velocity in feet per minute (fpm) <br /> C = Orifice Coefficient = 0 65 (for orifice used) <br /> K = Constant = 794 6 for mm water or 2929 8 for mm <br /> mercury <br /> P = Pressure differential across the orifice <br /> Q = Flow rate in cubic feet per minute (CFM) <br /> A = Area orifice in square feet 1" = 0 . 00545 ft2 <br /> Q = A X 0 65 X 794 6 X sqr (P) <br /> CALCULATIONS <br /> To calculate the pounds (lb) per day the concentration is multiplied <br /> by the volume of air produced in one day <br /> The lab reports the Concentrations (C) of the air sampling in <br /> /liter Thi first stern, i c t;n (-nn-vi-rt this value to lbs/cf (pounds <br /> per cubic foot) 1 ug/l x 0 00000ig/ug x 0 0022051/g x 28 . 321/cf = <br /> 0 0000000621lb/cf <br /> The volume of air produced in one day, equals the flow rate (Q) x the <br /> time of flow <br /> V = Q x T = cf/day = cf/min x 1440min/day <br /> 5 R603 APPEND. D <br />