Respirable Crystalline Silica (RCS)
WOHL performs analysis for RCS including quartz, cristobalite and tridymite via X-ray diffraction based on OSHA ID-142. X-ray diffraction for the determination of RCS is the preferred technique for almost all samples. It can differentiate forms of RCS that IR analysis cannot. IR analysis is typically only used where you have a well-defined matrix like coal dust.
WOHL uses three separate peaks for the determination of both quartz and cristobalite, and two separate peaks for the determination of tridymite. This greatly reduces the likelihood of reporting out high results due to interferences. The reporting levels (RL) are: quartz RL = 5 µg/sample, cristobalite RL = 10 µg/sample and tridymite RL = 10 µg/sample.
Respirable crystalline silica is collected on pre-weighed, 5 micron PVC filters using a sampler capable of collecting the respirable fraction. Examples of samplers capable of this are cyclones and Parallel Particle Impactors from SKC (PPI’s). There are many types of cyclones, but the two most common are the SKC aluminum cyclone and the 10 mm nylon cyclone. The 10 mm nylon cyclones typically use two-piece, 37 mm cassettes and the aluminum cyclone typically uses three-piece, 37 mm cassettes. Refer to the manufacturer’s recommended flow rates for proper respirable sampling. Request the proper filter, two- or three-piece polystyrene cassettes, to fit your cyclone. The laboratory can provide samplers the PPI’s. They come in 3 varieties (different flow rates): 2 lpm, 4 lpm, and 8 lpm. Typically the 4 and 8 lpm samplers are used only for task-based sampling and may overload quickly with longer term sampling. The PPI’s are disposable and come with pre-weighed PVC filters from WOHL. There is a special charge for these due to their cost.
Silica analysis can also be performed on total dust samples using PVC filters without a cyclone. Bulk samples are not required but can be analyzed.