where:
cst = average concentration of particulate matter, mg/dscm (gr/dscf).
csi = concentration of particulate matter from control device "i", mg/dscm (gr/dscf).
n = total number of control devices tested.
Qsdi = volumetric flow rate of stack gas from control device "i", dscm/hr (dscf/hr).
40 C.F.R. §60.275