Abstract
The inherent variability of three types of sampling trains commonly used in industrial hygiene field work were compared to that of a “control” sampling train in a laboratory setting. Eight quartets of samples were taken for each sampling train inside a cubic meter aerosol chamber in which Portland cement dust was generated. Side one, used as a control, had each of four sampling cassettes connected to a 2 Lpm critical orifice. Each orifice was connected by manifold to a Little Giant® pump. Side two had four sampling cassettes, each attached to a MSA Model G pump, and the ball setting of each rotameter was adjusted every half hour during sampling. Side three also had four sampling cassettes, each attached to an MSA Model G pump. The rotameters of these pumps were not adjusted during sampling. In the fourth side of the chamber four sampling cassettes were each connected to a DuPont “Constant Flow” Pump, Model P-2500. The variability in concentration among the four samples for each sampling train was calculated and compared to the other three sampling trains. The MSA Model G pumps in which the rotameter was adjusted every half hour during sampling had over twice as much variability as the other three sampling trains with a coefficient of variation of 5.80%. The MSA Model G pump with the unchanged rotameter had 2.48%, the DuPont, 2.21%, and the critical orifice, 2.20%.