Parallel Particle Impactors New Personal Samplers for Accurate Assessment of Worker Exposure to Respirable or Thoracic Dust Saulius Trakumas, Peter M. Hall, and Donald L. Smith SKC Inc., Eighty Four, Pennsylvania www.skcinc.com
Sampler should approximate particle penetration through human respiratory tract when purpose of monitoring workers exposure to airborne particulates is healthrelated.
ACGIH, CEN, and ISO have defined sampling conventions for size-selective sampling of airborne health-related particles: Inhalable (particles that enter nose/mouth) Thoracic (fraction of particles that penetrates down to the larynx) Respirable (fraction of particles that penetrates down to the alveolar region of the lungs)
Size-selective Sampling Conventions for Health-related Airborne Particulates Sampling Efficiency, E, % 5 5 Respirable Thoracic Inhalable
Size-selective Particle Samplers Cyclone
Performance of Six Respirable Cyclones Dorr-Oliver Dorr-Oliver Cyclone, Q S =.7 L/min GS-3 GS-3 Cyclone, Q S =. L/min GS- GS- Cyclone, Q S =. L/min Sampling Efficiency, E, % 5 5 Test Aerosol: DOP Glass Spheres Coal Mine Dust Sampling Efficiency, E, % 5 5 Test Aerosol: DOP Glass Spheres Coal Mine Dust Sampling Efficiency, E, % 5 5 Test Aerosol: DOP Glass Spheres Coal Mine Dust Respirable Convention Respirable Convention Respirable Convention 4 6 8 4 6 8 4 6 8 Aluminum BGI-4CP SIMPED Aluminum Cyclone, Q S =.5 L/min BGI-4CP Cyclone, Q S =. L/min SIMPED Cyclone, Q S =. L/min Sampling Efficiency, E, % 5 5 Test Aerosol: DOP Glass Spheres Coal Mine Dust Sampling Efficiency, E, % 5 5 Test Aerosol: DOP Glass Spheres Coal Mine Dust Sampling Efficiency, E, % 5 5 Test Aerosol: DOP Glass Spheres Coal Mine Dust Respirable Convention Respirable Convention Respirable Convention 4 6 8 4 6 8 4 6 8
Size-selective Particle Samplers Cyclone Foam
Size-selective Particle Samplers Cyclone Foam Horizontal elutriator
Size-selective Particle Samplers Cyclone Foam Horizontal elutriator Conventional impactor
Simulation of Respirable Curve Using Impactors Six impactors: d 5 =7., 5.4, 4.4, 3.7, 3., and.8 µm Four impactors: d 5 =6.6, 4.6, 3.5, and. µm Penetration, P, % 5 5 Two impactors: d 5 =5.6, and.9 µm Respirable Convention Single Impactor: d 5 =4. µm 4 6 8
V. Marple s design of multiple-nozzle, singlestage impactor* W W D 5 = 9µ WSt CV ρ p 5 Re = 5 ρ WV µ P = ρ V Q s =. Lpm D 5,µm 6.4 5. 5.8 4..5 3.5 3... d in, mm.3.5.4.63.87..48.33. No. of nozzles 6 58 3 53 9 * Virgil A. Marple. 978. Simulation of Respirable Penetration Characteristics by Inertial Impaction. J. Aerosol Sci., Vol.9, pp.5-34.
Parallel Particle Impactor (PPI) V P ρ = iout iin i P P P + =... NOut NIn Out In Out In V V V V V V ρ ρ ρ ρ ρ ρ + = = + = + + = = + = +... NOut NIn N Out In Out In S S Q S S Q S S Q W in W in *US Patent pending W out W out
Parallel Particle Impactor Prototype Respirable PPI (Q s =. Lpm) D 5,µm d in, mm d out, mm 6.6.59.3 4.6.6.33 3.5.73.4..3.59 Thoracic PPI (Q s =. Lpm) D 5,µm d in, mm d out, mm 7.5 5...9 4..8 8.9 3.5.5 4.8. 5.
Clean Air (5 Lpm) Virtual Impactor Clear Plexiglass Cylinder (D=, H=48 ) Test Device Sampling Lines To Filter Aerosol Generator Charge Neutralizer Turbulence Generators Honeycomb Flow Straightener Access Port Foam Experimental Setup Test aerosol used: DOP PST Glass Spheres Coal Mine Dust CDown( d) E( d) = % C ( d) Up Ball Valve Aerodynamic Particle Sizer (APS 33) Makeup Flow
APS was calibrated periodically using PSL particles of known size To minimize erroneous counts and coincidence effect, small test particles were removed before entering test chamber using a virtual impactor and test particle concentration inside the chamber was kept below cm -3.
Experimental Setup
Performance of Individual Impactors of Respirable PPI Prototype Penetration, P, % 5 5 Impactor 5% cut-off, d 5 No Design Measured 6.6 6.4 4.6 4.7 3 3.5 3.6 4..3 Q S =.5 L/min PST test particles 4 6 8
Overall Performance of Respirable PPI Prototype Penetration, P, % 5 5 Respirable Convention Curve constructed using experimental data obtained for each individual impactor Performance of whole sampler Performance of sampler exposed to coal mine dust for 6 hours (~ 4.5 mg/m 3 ) Q S =. L/min PST test particles 4 6 8
Performance of Respirable PPI Prototype when Tested Using Different Test Particles Test Particles: Penetration, P, % 5 5 PST (ρ p =.79 g/cc) Glass Spheres (ρ p =.5 g/cc) DOP (ρ p =.99 g/cc) Respirable Convention 4 6 8
Comparison of Performance of Respirable PPI Prototype and HD Cyclone Penetration, P, % 5 5 HD Cyclone, Q S =. L/min PPI, Q S =. L/min Respirable Convention 4 6 8
Bias Maps of Respirable PPI Prototype and HD Cyclone Geometric Standard Deviation, GSD 3.5 3..5..5 3.5 3..5..5 <-% -%< <-5% -5%< <5% 5%< <% >% 3 5 7 9 3 5 7 9 3 5 Mass Median Diameter, MMAD Respirable PPI prototype HD Cyclone
Parallel Particle Impactor Final Design Inlet Impaction Plate Exhaust
Performance of Respirable and Thoracic PPIs Penetration, P, % 5 5 Respirable Convention Thoracic PPI Thoracic Convention Respirable PPI.5 5 5
Conclusion A novel design incorporating several inertial impactors arranged in parallel was applied to fabricate respirable and thoracic PPIs. PPIs were found to follow accurately appropriate conventions. PPI samplers performed equally well for liquid and solid test particles and penetration characteristics remained unchanged after prolonged exposure to coal mine dust.
Conclusion The suggested PPI design can be applied to model a sampler with characteristics simulating the shape of any monotonically changing predetermined curve at a selected flow rate.