Volumetric Flow Q of air at STP where friction loss per unit length Δp / L (SI kg / m2 / s2) is, resp., 0.082, 0.245, and 0.816., for selected Nominal Duct Sizes[19] in smooth duct (ε = 50μm.) Δp / L 0.082 0.245 0.816 kg / m2 / s2 Duct size Q Q Q in mm cfm m3/s cfm m3/s cfm m3/s 2½ 63 3 0.0012 5 0.0024 10 0.0048 3¼ 80 5 0.0024 10 0.0046 20 0.0093 4 100 10 0.0045 18 0.0085 36 0.0171 5 125 18 0.0083 33 0.0157 66 0.0313 6 160 35 0.0163 65 0.0308 129 0.0611 8 200 64 0.0301 119 0.0563 236 0.1114 10 250 117 0.0551 218 0.1030 430 0.2030 12 315 218 0.1031 407 0.1919 799 0.3771 16 400 416 0.1965 772 0.3646 1513 0.7141 20 500 759 0.3582 1404 0.6627 2743 1.2945 24 630 1411 0.6657 2603 1.2285 5072 2.3939 32 800 2673 1.2613 4919 2.3217 9563 4.5131 40 1000 4847 2.2877 8903 4.2018 17270 8.1504 48 1200 7876 3.7172 14442 6.8161 27969 13.2000