Air volume measurement error in pumps with rotameters and high range “constant flow” pumps

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 calculat...