National Institute for Occupational Safety and Health

“ Non-fibrous cellulose. Very large cellulose fibers and cellulose fibers with convoluted shapes might interfere with fibers characterization. Other fiber types are typically rare and then only in trace amounts. ”

“ Cellulose fibers are easily distinguished from asbestos and glass fibers by morphology [3] . Do not count any fibers that have parallel sides. Do no t approach c loser than 3 viewing fields from the edg e of the filter. Under certain conditions, electrostatic charge may affect the sampling of fibers. These electrostatic effects are mo st likely to occur when the relative hum idity is low (during dry applicatio n) , and when sam pling is perform ed near the source of a erosol. T he res ult is that depo sition of fibers on the filter is reduc ed, espe cially near the edge of the filter. ”

“ Adjust m agnification to ~1200X and find the center of the filter using the X-Y m anipulators. Fields are exa m ined at regular intervals from the cente r of the filter along a trave rse in one direction. 14. Determine the area of the viewing field at this magnification using the inscribed or overlain calibrated sca le. 15. Count fibers in each field; distinguish, based upon morphology, between cellulose and other fiber types and make note of the relative proportion of fibrous to non-fibrous material in the field. ”