What are the “B” counting rules?
The “B” counting rules are alternate counting rules contained in the NIOSH 7400 method. The “B” rules are slightly different from the “A” rules and are to be used for nonasbestos fiber counting such as fiberglass and man-made mineral fibers. The OSHA regulations (29 CFR 1910.1001) require the analyst to only count fibers equal to or longer than 5 µm with a length-to-width ratio of 3:1 or greater. This is consistent with the “A” counting rules outlined in the NIOSH 7400 method. The “A” counting rules must be used to maintain compliance with AAR program requirements and must also be used in the PAT program.
The “B” counting rules are alternate counting rules contained in the NIOSH 7400 method. The “B” rules are slightly different from the “A” rules and are to be used for nonasbestos fiber counting such as fiberglass and man-made mineral fibers. The OSHA regulations (29 CFR 1910.1001) require the analyst to only count fibers equal to or longer than 5 µm with a length-to-width ratio of 3:1 or greater. This is consistent with the “A” counting rules outlined in the NIOSH 7400 method. The “A” counting rules must be used to maintain compliance with AAR program requirements and must also be used in the IHPAT program.
