Table 1 shows characteristics of each site sampled, including fluid and collector information. The three-stage cartridge consisted of an initial metal mesh filter followed by a cartridge filter with wrap and a HEPA filter. The two-stage cartridge lacked the final HEPA filter. The individual pleated cartridge had no additional filters present. Several sites where metal machining was done used metalworking fluids such as straight oil, soluble oil and semi-synthetic fluid.
Synthetic fluids contain primarily organic and inorganic salts but no petroleum compounds.
Typically synthetic fluids contain amines, nitrate, phosphates, and chlorine. Sampling time ranged from three minutes to two hours and varied with inlet concentration so that obtained samples could be analyzed readily. Isokinetic sampling was not necessary because the incoming particles were small and sampling was usually done from an inlet plenum where gas velocities were low. The size and quantity of solid particles and liquid droplets present were noted, and photographs were taken. A cumulative size distribution by mass was developed for each impactor run from which median diameter, d50, and geometric standard deviation, sg, were determined.