Metal Working Fluids
WOHL has validated a method, based on NIOSH method 5524, for determining the amount of metal working fluids (MWF) present in areas of their use. The method is a gravimetric procedure in which the collected fluid is extracted with a suitable solvent for that fluid. Weight loss after extraction is assumed to be equivalent to the amount of MWF present in the sample. Since a pre-weighed filter is used, the total particulate exposure is also determined in this procedure.
Samples are collected on a pre-weighed Teflon filter. Recommended flow rate for the total MWF is 2 liters per minute with a 960 liter collection volume (8 hours) and 1.6 liters per minute for the thoracic samples (768 liters). It is important to submit a bulk sample of the MWF used with each sample set to allow the lab to determine the appropriate solvent for use in the extraction procedure. In areas of high exposures the IH should use their judgement in sampling so as to not overload the filter.
The recommended method for mineral oil mists continues to be NIOSH 5026. For this method, collection on 5 micron pvc filters is recommended.