Abstract

Inadvertent inhalation of asbestos fibers and the subsequent development of incurable cancers is a leading cause of work-related deaths worldwide. Currently, there is no real-time in situ method for detecting airborne asbestos. We describe an optical method that seeks to address this deficiency. It is based on the use of laser light scattering patterns to determine the change in angular alignment of individual airborne fibers under the influence of an applied magnetic field. Detection sensitivity estimates are given for both crocidolite (blue) and chrysotile (white) asbestos. The method has been developed with the aim of providing a low-cost warning device to tradespeople and others at risk from inadvertent exposure to airborne asbestos.

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References

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  1. Testimony of NIOSH on occupational exposure to asbestos, tremolite, anthrophyllite and actinolite. 29CFR, Parts 1910 and 1926. 9 May, 1990.
  2. World Health Organization, Factsheet Number 343 – July 2010. http://www.who.int/mediacentre/factsheets/fs343/en/index.html
  3. P. Lilienfeld, P. B. Elterman, and P. Baron, “Development of a prototype fibrous aerosol monitor,” Am. Ind. Hyg. Assoc. J.40(4), 270–282 (1979).
    [CrossRef] [PubMed]
  4. A. P. Rood, E. J. Walker, and D. Moore, “Construction of a portable fiber monitor measuring the differential light scattering from aligned fibers,” Aerosol Sci. Technol.17(1), 1–8 (1992).
    [CrossRef]
  5. E. Kauffer, P. Martin, M. Grzebyk, M. Villa, and J. C. Vigneron, “Comparison of two direct-reading instruments (FM-7400 and Fibrecheck FC-2) with phase contrast optical microscopy to measure the airborne fibre number concentration,” Ann. Occup. Hyg.47(5), 413–426 (2003).
    [CrossRef] [PubMed]
  6. C. F. Bohren and D. R. Huffman, Absorption and Scattering of Light by Small Particles (Wiley,1983), Chap. 8.
  7. E. Hirst and P. H. Kaye, “Experimental and theoretical light scattering profiles from spherical and non-spherical particles,” J. Geophys. Res-Atmos.101(D14), 19231–19235 (1996).
  8. P. H. Kaye, “Spatial light scattering as a means of characterizing and classifying non-spherical particles,” Meas. Sci. Technol.9(2), 141–149 (1998).
    [CrossRef]
  9. K. B. Aptowicz, R. G. Pinnick, S. C. Hill, Y. L. Pan, and R. K. Chang, “Optical scattering patterns from single urban aerosol particles at Adelphi, Maryland, USA: A classification relating to particle morphologies,” J. Geophys. Res.111(D12), D12212 (2006).
    [CrossRef]
  10. P. H. Kaye, K. Aptowitz, R. K. Chang, V. Foot, and G. Videen, “Angularly resolved elastic scattering from airborne particles,” in Optics of Biological Particles, A. Hoekstra, V. Maltsev, G. Videen, eds., 31–61 (Springer, 2007).
  11. R. Cotton, S. Osborne, Z. Ulanowski, E. Hirst, P. H. Kaye, and R. S. Greenaway, “The ability of the Small Ice Detector (SID-2) to characterize cloud particle and aerosol morphologies obtained during flights of the FAAM BAe-146 research aircraft,” J. Atmos. Ocean. Technol.27(2), 290–303 (2010).
    [CrossRef]
  12. E. Hirst, P. H. Kaye, and J. A. Hoskins, “Potential for recognition of airborne asbestos fibres from spatial light scattering profiles,” Ann. Occup. Hyg.35(5), 623–632 (1995).
  13. P. Kaye, E. Hirst, and Z. Wang-Thomas, “Neural-network-based spatial light-scattering instrument for hazardous airborne fiber detection,” Appl. Opt.36(24), 6149–6156 (1997).
    [CrossRef] [PubMed]
  14. V. Timbrell, “Alignment of respirable asbestos fibres by magnetic fields,” Ann. Occup. Hyg.18(4), 299–311 (1975).
    [CrossRef] [PubMed]
  15. P. Lilienfeld, “Method and apparatus for real time asbestos aerosol monitoring,” US patent 4,940,327. Filed Oct. 25 (1988).
  16. Z. Ulanowski and P. H. Kaye, “Magnetic Anisotropy of Asbestos Fibers,” Appl. Phys. (Berl.)85(8), 4104–4109 (1999).
  17. V. Prodi, T. De Zaiacomo, D. Hochrainer, and K. Spurny, “Fibre collection and measurement with the inertial spectrometer,” J. Aerosol Sci.13(1), 49–58 (1982).
    [CrossRef]
  18. L. Jianzhong, Z. Weifeng, and Y. Zhaosheng, “Numerical research on the orientation distribution of fibers immersed in laminar and turbulent pipe flows,” J. Aerosol Sci.35(1), 63–82 (2004).
    [CrossRef]
  19. R. E. Walpole and R. H. Myers, Probability and Statistics for Engineers and Scientists, 5th edition (Macmillan, 1993) Chap.10.

2010

R. Cotton, S. Osborne, Z. Ulanowski, E. Hirst, P. H. Kaye, and R. S. Greenaway, “The ability of the Small Ice Detector (SID-2) to characterize cloud particle and aerosol morphologies obtained during flights of the FAAM BAe-146 research aircraft,” J. Atmos. Ocean. Technol.27(2), 290–303 (2010).
[CrossRef]

2006

K. B. Aptowicz, R. G. Pinnick, S. C. Hill, Y. L. Pan, and R. K. Chang, “Optical scattering patterns from single urban aerosol particles at Adelphi, Maryland, USA: A classification relating to particle morphologies,” J. Geophys. Res.111(D12), D12212 (2006).
[CrossRef]

2004

L. Jianzhong, Z. Weifeng, and Y. Zhaosheng, “Numerical research on the orientation distribution of fibers immersed in laminar and turbulent pipe flows,” J. Aerosol Sci.35(1), 63–82 (2004).
[CrossRef]

2003

E. Kauffer, P. Martin, M. Grzebyk, M. Villa, and J. C. Vigneron, “Comparison of two direct-reading instruments (FM-7400 and Fibrecheck FC-2) with phase contrast optical microscopy to measure the airborne fibre number concentration,” Ann. Occup. Hyg.47(5), 413–426 (2003).
[CrossRef] [PubMed]

1999

Z. Ulanowski and P. H. Kaye, “Magnetic Anisotropy of Asbestos Fibers,” Appl. Phys. (Berl.)85(8), 4104–4109 (1999).

1998

P. H. Kaye, “Spatial light scattering as a means of characterizing and classifying non-spherical particles,” Meas. Sci. Technol.9(2), 141–149 (1998).
[CrossRef]

1997

1996

E. Hirst and P. H. Kaye, “Experimental and theoretical light scattering profiles from spherical and non-spherical particles,” J. Geophys. Res-Atmos.101(D14), 19231–19235 (1996).

1995

E. Hirst, P. H. Kaye, and J. A. Hoskins, “Potential for recognition of airborne asbestos fibres from spatial light scattering profiles,” Ann. Occup. Hyg.35(5), 623–632 (1995).

1992

A. P. Rood, E. J. Walker, and D. Moore, “Construction of a portable fiber monitor measuring the differential light scattering from aligned fibers,” Aerosol Sci. Technol.17(1), 1–8 (1992).
[CrossRef]

1982

V. Prodi, T. De Zaiacomo, D. Hochrainer, and K. Spurny, “Fibre collection and measurement with the inertial spectrometer,” J. Aerosol Sci.13(1), 49–58 (1982).
[CrossRef]

1979

P. Lilienfeld, P. B. Elterman, and P. Baron, “Development of a prototype fibrous aerosol monitor,” Am. Ind. Hyg. Assoc. J.40(4), 270–282 (1979).
[CrossRef] [PubMed]

1975

V. Timbrell, “Alignment of respirable asbestos fibres by magnetic fields,” Ann. Occup. Hyg.18(4), 299–311 (1975).
[CrossRef] [PubMed]

Aptowicz, K. B.

K. B. Aptowicz, R. G. Pinnick, S. C. Hill, Y. L. Pan, and R. K. Chang, “Optical scattering patterns from single urban aerosol particles at Adelphi, Maryland, USA: A classification relating to particle morphologies,” J. Geophys. Res.111(D12), D12212 (2006).
[CrossRef]

Baron, P.

P. Lilienfeld, P. B. Elterman, and P. Baron, “Development of a prototype fibrous aerosol monitor,” Am. Ind. Hyg. Assoc. J.40(4), 270–282 (1979).
[CrossRef] [PubMed]

Chang, R. K.

K. B. Aptowicz, R. G. Pinnick, S. C. Hill, Y. L. Pan, and R. K. Chang, “Optical scattering patterns from single urban aerosol particles at Adelphi, Maryland, USA: A classification relating to particle morphologies,” J. Geophys. Res.111(D12), D12212 (2006).
[CrossRef]

Cotton, R.

R. Cotton, S. Osborne, Z. Ulanowski, E. Hirst, P. H. Kaye, and R. S. Greenaway, “The ability of the Small Ice Detector (SID-2) to characterize cloud particle and aerosol morphologies obtained during flights of the FAAM BAe-146 research aircraft,” J. Atmos. Ocean. Technol.27(2), 290–303 (2010).
[CrossRef]

De Zaiacomo, T.

V. Prodi, T. De Zaiacomo, D. Hochrainer, and K. Spurny, “Fibre collection and measurement with the inertial spectrometer,” J. Aerosol Sci.13(1), 49–58 (1982).
[CrossRef]

Elterman, P. B.

P. Lilienfeld, P. B. Elterman, and P. Baron, “Development of a prototype fibrous aerosol monitor,” Am. Ind. Hyg. Assoc. J.40(4), 270–282 (1979).
[CrossRef] [PubMed]

Greenaway, R. S.

R. Cotton, S. Osborne, Z. Ulanowski, E. Hirst, P. H. Kaye, and R. S. Greenaway, “The ability of the Small Ice Detector (SID-2) to characterize cloud particle and aerosol morphologies obtained during flights of the FAAM BAe-146 research aircraft,” J. Atmos. Ocean. Technol.27(2), 290–303 (2010).
[CrossRef]

Grzebyk, M.

E. Kauffer, P. Martin, M. Grzebyk, M. Villa, and J. C. Vigneron, “Comparison of two direct-reading instruments (FM-7400 and Fibrecheck FC-2) with phase contrast optical microscopy to measure the airborne fibre number concentration,” Ann. Occup. Hyg.47(5), 413–426 (2003).
[CrossRef] [PubMed]

Hill, S. C.

K. B. Aptowicz, R. G. Pinnick, S. C. Hill, Y. L. Pan, and R. K. Chang, “Optical scattering patterns from single urban aerosol particles at Adelphi, Maryland, USA: A classification relating to particle morphologies,” J. Geophys. Res.111(D12), D12212 (2006).
[CrossRef]

Hirst, E.

R. Cotton, S. Osborne, Z. Ulanowski, E. Hirst, P. H. Kaye, and R. S. Greenaway, “The ability of the Small Ice Detector (SID-2) to characterize cloud particle and aerosol morphologies obtained during flights of the FAAM BAe-146 research aircraft,” J. Atmos. Ocean. Technol.27(2), 290–303 (2010).
[CrossRef]

P. Kaye, E. Hirst, and Z. Wang-Thomas, “Neural-network-based spatial light-scattering instrument for hazardous airborne fiber detection,” Appl. Opt.36(24), 6149–6156 (1997).
[CrossRef] [PubMed]

E. Hirst and P. H. Kaye, “Experimental and theoretical light scattering profiles from spherical and non-spherical particles,” J. Geophys. Res-Atmos.101(D14), 19231–19235 (1996).

E. Hirst, P. H. Kaye, and J. A. Hoskins, “Potential for recognition of airborne asbestos fibres from spatial light scattering profiles,” Ann. Occup. Hyg.35(5), 623–632 (1995).

Hochrainer, D.

V. Prodi, T. De Zaiacomo, D. Hochrainer, and K. Spurny, “Fibre collection and measurement with the inertial spectrometer,” J. Aerosol Sci.13(1), 49–58 (1982).
[CrossRef]

Hoskins, J. A.

E. Hirst, P. H. Kaye, and J. A. Hoskins, “Potential for recognition of airborne asbestos fibres from spatial light scattering profiles,” Ann. Occup. Hyg.35(5), 623–632 (1995).

Jianzhong, L.

L. Jianzhong, Z. Weifeng, and Y. Zhaosheng, “Numerical research on the orientation distribution of fibers immersed in laminar and turbulent pipe flows,” J. Aerosol Sci.35(1), 63–82 (2004).
[CrossRef]

Kauffer, E.

E. Kauffer, P. Martin, M. Grzebyk, M. Villa, and J. C. Vigneron, “Comparison of two direct-reading instruments (FM-7400 and Fibrecheck FC-2) with phase contrast optical microscopy to measure the airborne fibre number concentration,” Ann. Occup. Hyg.47(5), 413–426 (2003).
[CrossRef] [PubMed]

Kaye, P.

Kaye, P. H.

R. Cotton, S. Osborne, Z. Ulanowski, E. Hirst, P. H. Kaye, and R. S. Greenaway, “The ability of the Small Ice Detector (SID-2) to characterize cloud particle and aerosol morphologies obtained during flights of the FAAM BAe-146 research aircraft,” J. Atmos. Ocean. Technol.27(2), 290–303 (2010).
[CrossRef]

Z. Ulanowski and P. H. Kaye, “Magnetic Anisotropy of Asbestos Fibers,” Appl. Phys. (Berl.)85(8), 4104–4109 (1999).

P. H. Kaye, “Spatial light scattering as a means of characterizing and classifying non-spherical particles,” Meas. Sci. Technol.9(2), 141–149 (1998).
[CrossRef]

E. Hirst and P. H. Kaye, “Experimental and theoretical light scattering profiles from spherical and non-spherical particles,” J. Geophys. Res-Atmos.101(D14), 19231–19235 (1996).

E. Hirst, P. H. Kaye, and J. A. Hoskins, “Potential for recognition of airborne asbestos fibres from spatial light scattering profiles,” Ann. Occup. Hyg.35(5), 623–632 (1995).

Lilienfeld, P.

P. Lilienfeld, P. B. Elterman, and P. Baron, “Development of a prototype fibrous aerosol monitor,” Am. Ind. Hyg. Assoc. J.40(4), 270–282 (1979).
[CrossRef] [PubMed]

Martin, P.

E. Kauffer, P. Martin, M. Grzebyk, M. Villa, and J. C. Vigneron, “Comparison of two direct-reading instruments (FM-7400 and Fibrecheck FC-2) with phase contrast optical microscopy to measure the airborne fibre number concentration,” Ann. Occup. Hyg.47(5), 413–426 (2003).
[CrossRef] [PubMed]

Moore, D.

A. P. Rood, E. J. Walker, and D. Moore, “Construction of a portable fiber monitor measuring the differential light scattering from aligned fibers,” Aerosol Sci. Technol.17(1), 1–8 (1992).
[CrossRef]

Osborne, S.

R. Cotton, S. Osborne, Z. Ulanowski, E. Hirst, P. H. Kaye, and R. S. Greenaway, “The ability of the Small Ice Detector (SID-2) to characterize cloud particle and aerosol morphologies obtained during flights of the FAAM BAe-146 research aircraft,” J. Atmos. Ocean. Technol.27(2), 290–303 (2010).
[CrossRef]

Pan, Y. L.

K. B. Aptowicz, R. G. Pinnick, S. C. Hill, Y. L. Pan, and R. K. Chang, “Optical scattering patterns from single urban aerosol particles at Adelphi, Maryland, USA: A classification relating to particle morphologies,” J. Geophys. Res.111(D12), D12212 (2006).
[CrossRef]

Pinnick, R. G.

K. B. Aptowicz, R. G. Pinnick, S. C. Hill, Y. L. Pan, and R. K. Chang, “Optical scattering patterns from single urban aerosol particles at Adelphi, Maryland, USA: A classification relating to particle morphologies,” J. Geophys. Res.111(D12), D12212 (2006).
[CrossRef]

Prodi, V.

V. Prodi, T. De Zaiacomo, D. Hochrainer, and K. Spurny, “Fibre collection and measurement with the inertial spectrometer,” J. Aerosol Sci.13(1), 49–58 (1982).
[CrossRef]

Rood, A. P.

A. P. Rood, E. J. Walker, and D. Moore, “Construction of a portable fiber monitor measuring the differential light scattering from aligned fibers,” Aerosol Sci. Technol.17(1), 1–8 (1992).
[CrossRef]

Spurny, K.

V. Prodi, T. De Zaiacomo, D. Hochrainer, and K. Spurny, “Fibre collection and measurement with the inertial spectrometer,” J. Aerosol Sci.13(1), 49–58 (1982).
[CrossRef]

Timbrell, V.

V. Timbrell, “Alignment of respirable asbestos fibres by magnetic fields,” Ann. Occup. Hyg.18(4), 299–311 (1975).
[CrossRef] [PubMed]

Ulanowski, Z.

R. Cotton, S. Osborne, Z. Ulanowski, E. Hirst, P. H. Kaye, and R. S. Greenaway, “The ability of the Small Ice Detector (SID-2) to characterize cloud particle and aerosol morphologies obtained during flights of the FAAM BAe-146 research aircraft,” J. Atmos. Ocean. Technol.27(2), 290–303 (2010).
[CrossRef]

Z. Ulanowski and P. H. Kaye, “Magnetic Anisotropy of Asbestos Fibers,” Appl. Phys. (Berl.)85(8), 4104–4109 (1999).

Vigneron, J. C.

E. Kauffer, P. Martin, M. Grzebyk, M. Villa, and J. C. Vigneron, “Comparison of two direct-reading instruments (FM-7400 and Fibrecheck FC-2) with phase contrast optical microscopy to measure the airborne fibre number concentration,” Ann. Occup. Hyg.47(5), 413–426 (2003).
[CrossRef] [PubMed]

Villa, M.

E. Kauffer, P. Martin, M. Grzebyk, M. Villa, and J. C. Vigneron, “Comparison of two direct-reading instruments (FM-7400 and Fibrecheck FC-2) with phase contrast optical microscopy to measure the airborne fibre number concentration,” Ann. Occup. Hyg.47(5), 413–426 (2003).
[CrossRef] [PubMed]

Walker, E. J.

A. P. Rood, E. J. Walker, and D. Moore, “Construction of a portable fiber monitor measuring the differential light scattering from aligned fibers,” Aerosol Sci. Technol.17(1), 1–8 (1992).
[CrossRef]

Wang-Thomas, Z.

Weifeng, Z.

L. Jianzhong, Z. Weifeng, and Y. Zhaosheng, “Numerical research on the orientation distribution of fibers immersed in laminar and turbulent pipe flows,” J. Aerosol Sci.35(1), 63–82 (2004).
[CrossRef]

Zhaosheng, Y.

L. Jianzhong, Z. Weifeng, and Y. Zhaosheng, “Numerical research on the orientation distribution of fibers immersed in laminar and turbulent pipe flows,” J. Aerosol Sci.35(1), 63–82 (2004).
[CrossRef]

Aerosol Sci. Technol.

A. P. Rood, E. J. Walker, and D. Moore, “Construction of a portable fiber monitor measuring the differential light scattering from aligned fibers,” Aerosol Sci. Technol.17(1), 1–8 (1992).
[CrossRef]

Am. Ind. Hyg. Assoc. J.

P. Lilienfeld, P. B. Elterman, and P. Baron, “Development of a prototype fibrous aerosol monitor,” Am. Ind. Hyg. Assoc. J.40(4), 270–282 (1979).
[CrossRef] [PubMed]

Ann. Occup. Hyg.

E. Hirst, P. H. Kaye, and J. A. Hoskins, “Potential for recognition of airborne asbestos fibres from spatial light scattering profiles,” Ann. Occup. Hyg.35(5), 623–632 (1995).

E. Kauffer, P. Martin, M. Grzebyk, M. Villa, and J. C. Vigneron, “Comparison of two direct-reading instruments (FM-7400 and Fibrecheck FC-2) with phase contrast optical microscopy to measure the airborne fibre number concentration,” Ann. Occup. Hyg.47(5), 413–426 (2003).
[CrossRef] [PubMed]

V. Timbrell, “Alignment of respirable asbestos fibres by magnetic fields,” Ann. Occup. Hyg.18(4), 299–311 (1975).
[CrossRef] [PubMed]

Appl. Opt.

Appl. Phys. (Berl.)

Z. Ulanowski and P. H. Kaye, “Magnetic Anisotropy of Asbestos Fibers,” Appl. Phys. (Berl.)85(8), 4104–4109 (1999).

J. Aerosol Sci.

V. Prodi, T. De Zaiacomo, D. Hochrainer, and K. Spurny, “Fibre collection and measurement with the inertial spectrometer,” J. Aerosol Sci.13(1), 49–58 (1982).
[CrossRef]

L. Jianzhong, Z. Weifeng, and Y. Zhaosheng, “Numerical research on the orientation distribution of fibers immersed in laminar and turbulent pipe flows,” J. Aerosol Sci.35(1), 63–82 (2004).
[CrossRef]

J. Atmos. Ocean. Technol.

R. Cotton, S. Osborne, Z. Ulanowski, E. Hirst, P. H. Kaye, and R. S. Greenaway, “The ability of the Small Ice Detector (SID-2) to characterize cloud particle and aerosol morphologies obtained during flights of the FAAM BAe-146 research aircraft,” J. Atmos. Ocean. Technol.27(2), 290–303 (2010).
[CrossRef]

J. Geophys. Res-Atmos.

E. Hirst and P. H. Kaye, “Experimental and theoretical light scattering profiles from spherical and non-spherical particles,” J. Geophys. Res-Atmos.101(D14), 19231–19235 (1996).

J. Geophys. Res.

K. B. Aptowicz, R. G. Pinnick, S. C. Hill, Y. L. Pan, and R. K. Chang, “Optical scattering patterns from single urban aerosol particles at Adelphi, Maryland, USA: A classification relating to particle morphologies,” J. Geophys. Res.111(D12), D12212 (2006).
[CrossRef]

Meas. Sci. Technol.

P. H. Kaye, “Spatial light scattering as a means of characterizing and classifying non-spherical particles,” Meas. Sci. Technol.9(2), 141–149 (1998).
[CrossRef]

Other

P. H. Kaye, K. Aptowitz, R. K. Chang, V. Foot, and G. Videen, “Angularly resolved elastic scattering from airborne particles,” in Optics of Biological Particles, A. Hoekstra, V. Maltsev, G. Videen, eds., 31–61 (Springer, 2007).

C. F. Bohren and D. R. Huffman, Absorption and Scattering of Light by Small Particles (Wiley,1983), Chap. 8.

Testimony of NIOSH on occupational exposure to asbestos, tremolite, anthrophyllite and actinolite. 29CFR, Parts 1910 and 1926. 9 May, 1990.

World Health Organization, Factsheet Number 343 – July 2010. http://www.who.int/mediacentre/factsheets/fs343/en/index.html

R. E. Walpole and R. H. Myers, Probability and Statistics for Engineers and Scientists, 5th edition (Macmillan, 1993) Chap.10.

P. Lilienfeld, “Method and apparatus for real time asbestos aerosol monitoring,” US patent 4,940,327. Filed Oct. 25 (1988).

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Figures (10)

Fig. 1
Fig. 1

Scanning electron micrographs of crocidolite (blue) and chrysotile (white) asbestos. Samples were respirable reference materials from UICC (International Union Against Cancer).

Fig. 2
Fig. 2

Schematic illustration of spatial light scattering pattern acquisition from individual airborne particles. The example images shown were captured from particles using an intensified CCD camera as a detector. (Top row L-R): a ~9 µm water droplet, a cubic NaCl crystal (~4 µm), a straight crocidolite asbestos fiber, a cornflour grain, a 3 µm hematite ellipsoid. (Second row): a curved chrysotile asbestos fiber.

Fig. 3
Fig. 3

Distribution of calculated times for airborne asbestos fibers to rotate through 10° in the presence of a 0.5T magnetic field initially at 45° to the fibers. [Reproduced from J. App. Phys. 84, 8, 4104-4109 (1999)].

Fig. 4
Fig. 4

Schematic diagram of the Single-beam scattering system used to (a) differentiate fibers from non-fiber particles in the sample air and then (b) to measure the angle of orientation of the fiber particles relative to the airflow axis. The latter parameter can be used to indicate whether or not the fibers had been rotated during transit through the magnetic field, thereby indicating if they were asbestos. For clarity, the enclosure containing this optical assembly is not shown.

Fig. 5
Fig. 5

CMOS linear array scattering data from a crocidolite fiber (left), a droplet (center), and an irregular shaped silica dust grain (right). The inset images are for illustration only and show the relative positions of the arrays (red and green bars) superimposed on the type of scattering patterns that would produce the given array responses. (Note the slight vertical offset of the ‘green’ array data. This is due to a small (~0.25 mm) misalignment of the two array chips on their printed circuit board and is corrected for in subsequent data processing).

Fig. 6
Fig. 6

Example of Peak-to-Mean (PTM) ratios for airborne particles found background air in an asbestos-free building renovation site (solid line), contrasted with PTM ratios recorded from laboratory aerosols of chrysotile (dashed line) and crocidolite (dotted line) asbestos. (Approximately 3,000 particles are represented in each distribution).

Fig. 7
Fig. 7

Estimation of the fiber alignment angle (θ) of the fiber in the laser beam (beam cross-section shown as red ellipse) by measuring the separation of scattering peaks on the two CMOS arrays. The fiber itself is orthogonal to the line linking the scattering peaks, as indicated.

Fig. 8
Fig. 8

Distribution of the alignment angle (relative to the airflow axis) of crocidolite fibers both with (blue) and without (red) a magnetic field present. (2,380 and 2,393 fibers are represented in the blue and red plots, respectively).

Fig. 9
Fig. 9

Schematic diagram of the Dual-beam asbestos detection system. Inset: Cut-away 3D model of the actual Dual-beam system implementation.

Fig. 10
Fig. 10

Absolute change in angle of alignment of crocidolite asbestos fibers and gypsum fibers occurring during fiber transit through the magnetic field region of the Dual-beam system (magnets at 90° to the airflow). Some 2,300 fibers are represented in each population.

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