38
•
Start pump and run at about 1 liter/minute. Observe real-time concentration
(CONC) reading
•
Increase flow rate very slowly and gradually until CONC reading is one-half of
the initial concentration measured without the cyclone. Continue sampling at this
flow rate for about one minute and confirm that TWA reading is about one-half
of the initial one. Otherwise readjust flow rate. Note final flow rate at which the
TWA value has decreased to one-half the value noted without the cyclone.
•
Enter the final flow rate for which the TWA value is one-half of the initial value
into the graph of Fig. 7 and read the corresponding D50 particle size in
micrometers. This represents the mass median particle diameter of the aerosol.
For example, if the TWA value without the cyclone was 0.8 mg/m
3
, and the flow rate
(with the cyclone attached) required to reduce the TWA to 0.4 mg/m
3
is 2
liters/minute, the mass median particle size (as obtained from the curve of Fig. 7) is
approximately 5.5
μ
m.
