Dust Exposure Calculator

Respirable crystalline silica (RCS): 0.1 mg/m³. Hardwood dust: 3 mg/m³ (carcinogen). Portland cement dust (respirable): 4 mg/m³ (per EH40/2005 — same as the general respirable WEL). General inhalable dust: 10 mg/m³. General respirable dust: 4 mg/m³. These are 8-hour time-weighted averages.

Silica dust (from cutting concrete, stone, brick, mortar) causes silicosis - irreversible scarring of the lungs. It is also classified as a carcinogen (lung cancer). The WEL is very low (0.1 mg/m³) because even small amounts over time cause permanent damage. Use water suppression and on-tool extraction.

Inhalable dust is the larger fraction that enters the nose and mouth (general-dust WEL 10 mg/m³). Respirable dust is the finer fraction that penetrates deep into the lungs (general-dust WEL 4 mg/m³). The respirable crystalline silica WEL (0.1 mg/m³) is measured as the respirable fraction. The wood-dust WELs (hardwood 3 mg/m³, softwood 5 mg/m³) are measured as the inhalable fraction, per HSE EH40/2005.

On-tool dust extraction (vacuum attached to the tool) can reduce airborne dust by 80-95% when properly maintained. It is the most effective control after elimination and is required by HSE for silica-generating tasks. Always use an M-class or H-class vacuum extractor.

RPE must be used when engineering controls (extraction, water suppression) alone cannot reduce exposure below the WEL. For silica dust tasks, RPE is almost always needed alongside extraction. HSE CIS36 "Construction dust" (Revision 3) sets the general level for construction dust at an Assigned Protection Factor of 20, and its Table 2 lists nothing below that: an FFP3 disposable or a half mask with a P3 filter, or for longer duration work a TH2 powered hood or helmet. FFP1 (APF 4) and FFP2 (APF 10) are not adequate for construction dust. All tight-fitting RPE must be face-fit tested and the wearer clean-shaven at the seal.

No, and assuming they do is a common and dangerous mistake. HSE HSG53 "Respiratory protective equipment at work" (Fourth edition, 2013) gives powered devices three Assigned Protection Factors, not one. Figure 14 covers powered respirators with hoods and helmets to BS EN 12941: TH1 is APF 10, TH2 is APF 20, TH3 is APF 40, and no face-fit test is required because the facepiece is loose-fitting. Figure 13 covers powered respirators with masks to BS EN 12942: TM1 is APF 10, TM2 is APF 20, TM3 is APF 40, and a face-fit test IS required because those are tight-fitting. Treating a TH2 as APF 40 halves the exposure figure you calculate. Read the class marking on the device, and if you cannot find it, assume the lowest class it could be.