Gravimetric Analysis

Many airborne particulates are regulated by OSHA as "Particulates not otherwise regulated." These are dusts for which OSHA has not established a specific permissible exposure limit (PEL). Generally the dusts are classified as INHALABLE, TOTAL, THORACIC, and RERSPIRABLE based particle size or cut point. 

WOHL can provide pre-weighed 5 micron PVC filters in a variety of filter types.  The basic types are:  2 piece 37 mm polystyrene with yellow band, 3 piece 37 mm polystyrene with yellow band, 2 piece 37mm ESF filter with green band, 37 mm MSA "saucer" with white band, and 25 mm "goblet" with yellow tape for sampling behind a welding helmet.  WOHL also as pre-weighed 37mm 2 micron PTFE filters with blue band and green tape called MWF cassettes. 

It has been well documented that when dust samples are collected, some of the dusts adhere to the polystyrene cassette walls.  Depending on the type of dust, its particle size, and the electrostatic nature of the dust, this deposition can be substantial.  The laboratory has a filter to deal with issue.  We call them ESF filters.  They contain a capsule inside a standard 2 piece 37 mm polystyrene cassette ensuring all the dust collected in weighed.  This filter type can be used wherever a standard 2 piece 37 mm polystyrene cassette is used; however, it cannot be used where additional analysis is needed, like silica or metals, and it cannot be used with cyclones that require 3 piece cassettes.

Inhalable samples capture the largest sized particulates and are collected on special IOM samplers, which can be provided by the lab with many types of media.  Many current AGCIH TLV's for particulates have an inhalable notation on them. 

Total particulates are collected on pre-weighed 5 micron pore sized PVC filters using a closed faced cassette.  Many current OSHA PEL's are listed as "total".   

Thoracic samples are collected on pre-weighed 5 micron PVC filters using a special thoracic cyclone.  The laboratory can provide media, but not the cyclones.

Respirable particulates are collected on pre-weighed 5 micron PVC filters using a cyclone capable of collecting respirable particulates.  The are many types of these cyclones, but the 2 most common are the SKC aluminum cyclone and the 10 mm nylon cyclone.  The 10 mm nylon cyclones typically use 2 piece 37 mm cassettes, and SKC aluminum cyclones typically use 3 piece 37 mm cassettes.  Refer to the manufacturers recommended flow rate for proper respirable sampling.  Request the proper filter type, 2 piece or 3 piece polystyrene cassettes, to fit your cyclone.