Air Sampling for Particulate Matter [PDF]

Filter Selection. ◇ MCE filters. – Clears for microscopy. – Particle counting and sizing. – Fiber counting (asbe

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This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike License. Your use of this material constitutes acceptance of that license and the conditions of use of materials on this site.

Copyright 2006, The Johns Hopkins University, Patrick Breysse, and Peter S. J. Lees. All rights reserved. Use of these materials permitted only in accordance with license rights granted. Materials provided “AS IS”; no representations or warranties provided. User assumes all responsibility for use, and all liability related thereto, and must independently review all materials for accuracy and efficacy. May contain materials owned by others. User is responsible for obtaining permissions for use from third parties as needed.

Air Sampling for Particulate Matter Patrick N. Breysse, PhD, CIH Peter S.J. Lees, PhD, CIH Johns Hopkins University

Section A Introduction

Exposure Assessment Methods Š General air-sampling methodology

Air Pump

Flow Adjust

Collection Media

Air + Contaminant

4

General Sampling Methodology Š Personal sampling – Battery powered pump worn by worker Š Sample from “breathing zone” Š Area sampling – Sample from fixed location

5

Concentration Mass conta min ant Concentrat ion = Volume air Š Contaminant mass from laboratory analysis Š Air volume from product of calibrated air flow rate and sampling time

6

Section B Sample Pumps and Volume Determination

Personal Sampling Pumps

Source: Patrick Breysse

8

Sample Volume

V = Q T Š Where V is volume, L Š Q is flow rate, L/min Š T is sample time, min

(2.5 L / min) (480 min ) = 1,200 L (1,200 L ) (1m / 1000 L ) = 1.2 m 3

3

9

Source: U. S. Government

10

Pump Calibration Soap bubble flow meter

Pump Tubing Cassette

Source: Patrick Breysse

11

Frictionless Piston Flow Meter

Calibrator Source: Patrick Breysse

Tubing

Sample collector

Pump 12

Soap Bubble Flow Meter Š Measure time required for bubble to move through specified volume in burette

⎛ 1 . 0L ⎞ ⎛ 60 sec ⎞ ⎟ = 2 . 0L / min ⎟⎜ ⎜ ⎝ 30 sec ⎠ ⎝ min ⎠

13

Section C Sample Collection

Sampling for Aerosols Š Filtration is method of choice Š Filter defined by composition, diameter, and pore size Š General classes of filters used: – Membrane filter – Nuclepore filter

Source: Peter Lees

15

Filter Selection Š Membrane filter types – Mixed cellulose ester (MCE) – Teflon – Polyvinyl chloride Š Filter type selected primarily for compatibility with analytical method

Continued

16

Filter Selection Š MCE filters – Clears for microscopy – Particle counting and sizing – Fiber counting (asbestos) Š PVC filters – Do not absorb water vapor – Stable for gravimetric analysis Continued

17

Filter Selection Š Teflon filters – Low tare weight – Low mass gravimetric analysis

18

37 mm Filter Cassette Š Plastic cassette holds filter paper Š Filter collects “total” dust Š Filter diameter is 37 mm

Retaining Ring Filter paper Support Pad Source: Peter Lees

Continued

19

37 mm Filter Cassette

Source: Patrick Breysse

20

Filter Analysis Š Gravimetric (pre-weight minus postweight) Š Specific contaminant analysis – Metals – Silica – Fibers – Polyaromatic hydrocarbons

21

Impingers Š Old dust methods used microscopic counting of particles (mppcf) Š Current bioaerosol method (fungal spores and bacteria) Source: U. S. Government

Continued

22

Section D Size-Selective Samplers

Exposure Assessment Methods Š Size-selective air-sampling methodology Air Pump

Flow Adjust

Collection Media

Size Selector

Air + Contaminant

Š Size selector permits collection of more biologically-relevant aerosol fraction – Respirable fraction, thoracic fraction, inhalable fraction, PM10, PM 2.5 24

Size Selection: Impactors Š Multistage or single stage Š Multiple fractions of varying size ranges possible – Can be used to determine complete size distribution Š Flow rate dependent Š Commonly used for bioaerosol assessment Š Mostly area-type measurement because high flow rate required 25

S-Stage Impactor Schematic

Adapted by CTLT

26

Size Selection: Cyclones Š Cyclones are commonly used sizeselective samplers Š Used to define respirable particle sampling criteria – Cyclone removal mimics respiratory system when operated – Flow rate is critical

27

Cyclone Samplers To sample collection filter

Source: U.S. Government

Inertial Impaction

28

10 mm Dorr-Oliver Cyclone Filter cassette Cyclone inlet Cyclone body

Source: Patrick Breysse

29

Personal P10 and PM2.5 Impactors Š EPA regulates particles

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