Quartz = Cristobalite = Tridymite = Withdrawn OSHA PEL (Enforceable Standard) PEL (mg/m3) = 10 % Quartz+2(% Cris)+2(% Trid)+2Ģ8 Example OSHA Calculation Full Shift Using a SKC Cyclone Sample time (minutes) Sample Volume Liters=1.2 m3 Mass of Respirable Dust (mg) 855 ug = mg Dust Concentration 0.71 mg/m3 Mass Quartz Mass Cristobalite Mass Tridymite % Quartz % Cristobalite % Tridymite 44.5 ug 19.7 ug N.D.
ACGIH recommends that particle size selective threshold limit values (TLVs ) be expressed in three forms: Inhalable (100 µm 50% cut point), hazardous when deposited anywhere in the respiratory tract Thoracic (10 µm 50% cut point), hazardous when deposited in the lung airways and the gas exchange regions Respirable (4 µm 50% cut point), hazardous when deposited in the gas exchange regions of the lungsĢ5 Crystalline Silica Analysis Measures the three angles occurring from the x rays bouncing off of the crystalline silica Amorphous silica not measured as there is no crystalline structure X Rays Detector dĢ7 Interpreting Silica Results ACGIH TLV (mg/m3). 1 Dust Sampling Equipment Choice Equipment Use Interpreting Results Bill Walsh, CIH Galson LaboratoriesĢ Types of Dusts Encountered Respirable Dust Requires a sizing mechanism to screen out large particles Flow Rate is Critical to Sizing Mechanism Crystalline Silica Diesel Particulate matter (DPM) Total Dust Samples All Particulate in the Air Metal Fumes PNOC (Particulates not otherwise classified) Nuisance Dust Flow rate generally 2.0 LPM (Not Critical)ģ Size Selective Dusts The concept of size selective sampling of industrial aerosols is based on the measurement of particles that are associated with a specific human health effect, i.e., how deeply particles penetrate into the respiratory tract.
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