Industrial Hygiene Indoor Particles: Technology Copyright © 2008 by DBS

Contents Introduction Mass Measurement Number Measurement Size Distribution Measurement Overview of technologies

Introduction Active and passive collection required for further physical + chemical + biological analysis In-situ techniques measure physical particle characteristic in real time (mass, number, size distribution, surface area) –Maybe direct (e.g. optical counting) or indirect (oscillating microbalance) –Developing technology: real-time chemical/biological characterization (Gard et al., 1997; Hairston et al., 1997)

Introduction Analysis of Airborne Particles McMurry, 2000; Willeke and Baron, 2001; Schwela et al., 2002

Mass Measurement Methods Gravimetric Methods Beta Attenuation Methods Vibration Microbalance Methods Light-Scattering Methods

Mass Measurement Gravimetric Methods Determines mg/m 3 Draws large volume of air over 24 hr period –Glass fiber or membrane filter –Weighed before and after –0.3 to ~100 μm particle size ‘Hi-Vols’ are not suitable for indoor use due to flow rate Reeve, 2002

Mass Measurement Beta Attenuator Methods (BAM) Beta particles from 14 C source are attenuated (lose signal strength) as they pass through particulate deposits on a filter tape Absorption of radiation is proportional to mass of PM –Contunuous real-time measurement (no weighing required!) Range: µg/m 3 Temperature: -30° to +45°C New version is heated to remove moisture effects Willeke and Hinds, 2001

Mass Measurement Vibrational Microbalance Methods Tapered Element Oscillating Microbalance (TEOM) Air is drawn through a filter at the end of a tapered oscillating glass tube Change in frequency is directly related to the mass of PM accumulated Range: µg/m 3 Temperature: -30° to +45°C Patashnik and Ruprecht, 1980

Mass Measurement Light-Scattering Methods Concentration of airborne particles In-situ, real-time measurements Categories: –Nephelometers (wider angle) –Photometers

Mass Measurement Light-Scattering Instruments: Photometers Most common direct-reading instrument Pros: –Real-time –Simpler to use, direct reading –Less expensive (long-term) Signal is proportional to total volume (not mass), particle density must be used to derive mass concentration Introduces uncertainty in measurements pp Morawska and Salthammer, 2004

Morawska and Salthammer, 2003

Number Concentration Measurement Optical particle counters (OPCs) based on principle of light scattering by particles –Coincidence error – when 2 particles cross the beam at once –Limited to particles > 0.1 μm Condensation particle counters (CPC) –Particles drawn through n- butanol vapor –Magnifies particles by growth via condensation –Detects down to 10 nm

Size Distribution Measurements Mass distribution with particle size Multistage Impactor (gravimetric or TEOM) - Larger particles stick to impaction plates Number distribution with particle size Light scattering or Electrical Low-Pressure Impactor (ELPI) - Measures electric current of charged particles at each impaction stage (Marjamaki et al., 2000)

Surface Area Measurements Epiphaniometer – determines Fuchs aurface area of particles using radioactivity (Gaggeler et al 1989)

Technology Overview

Question There are currently several investigations to compare the results of different PM analyzers. What reasons could contribute to this concern? Measurements are dependent on atmospheric conditions Absorbed water may be difficult to control during operations Meteorological conditions may affect flow rate Each technique responds differently to individual particle sizes Some components are volatile and may be lost due to heat (TEOM)

References *Baron, P.A. and Willeke, K. (eds.) (2001) Aerosol Measurement. Wiley-Interscience, New York. *Gard, E., J. E. Mayer, B. D. Morrical, T. Dienes, D. P. Fergenson and K. A. Prather (1997). "Real-time analysis of individual atmospheric aerosol particles: Design and performance of a portable ATOFMS." Analytical Chemistry, Vol. 69, No. 20, pp *Hairston, P. P., Ho, J., and Quant, F. R. (1997) Design of an Instrument for Real-Time Detection of Bioaerosols Using Simultaneous Measurement of Particle Aerodynamic Size and Intrinsic Fluorescence. Aerosol Science Technology. Vol. 28, pp. 471–482. Willeke and Hinds, 2001 *Lai, A.C.K. (2002) Particle Deposition Indoors: A Review (Summary Version). Indoor Air, Vol. 12, pp Marjamaki, M., Keskinen, J., Chen, D.R., and Pui, D.Y.H. (2000) Performance Evaluation of the Electrical Low-Pressure Impactor (ELPI). Journal of Aerosol Science, Vol. 31, No. 2, pp *McMurry, P.H. (2000) A Review of Atmospheric Aerosol Measurements. Atmospheric Environment, Vol. 24, pp *Schwela, D., Morawska, L., and Kotzias, D. (eds.) (2002) Guidelines for Concentration and Exposure- Response Measurements of Fine and Ultra-Fine particulate Matter for Use in Epidemiological Studies. World Health Organization. Patashnik, H. and Ruprecht, G. (1980) A New Real Time Aerosol Mass Monitoring Instrument: The TEOM. Paper presented at the Proceedings of Advances in particulate Sampling and Measurement. *Willeke, K. and Baron, P.A. (eds.) (2001) Aerosol Measurement: Principles, Techniques and Applications (2 nd ed.). Van Nostrand Reinhold, New York.

Books Jacobson, M.Z. (2002) Atmospheric Pollution. Cambridge University Press, Cambridge. Morawska, L. and Salthammer, T. (eds.) (2003) Indoor Environment: Airborne particles and Settled Dust. Wiley-VCH. Vincent, J.H. (2007) Aerosol Sampling: Science, Standards, Instrumentation and Applications. Wiley.