Edwin Hirst

Simultaneous light scattering and intrinsic fluorescence measurement for the classification of airborne particles

We describe a prototype laboratory light-scattering instrument that integrates two approaches to airborne particle characterization: spatial light-scattering analysis and intrinsic fluorescence measurement, with the aim of providing an effective means of classifying biological particles within an ambient aerosol. The system uses a single continuous-wave 266-nm ultraviolet laser to generate both the spatial elastic scatter data (from which an assessment of particle size and shape is made) and the particle intrinsic fluorescence data from particles in the approximate size range of 1-10-mum diameter carried in a sample airflow through the laser beam. Preliminary results suggest that this multiparameter measurement approach can provide an effective means of classifying different particle types and can reduce occurrences of false-positive detection of biological aerosols.

A real‐time monitoring system for airborne particle shape and size analysis

This paper describes a new instrument for the study of airborne particles. The instrument performs a rapid analysis of the transient spatial intensity distribution of laser-light scattered by individual aerosol particles drawn from an ambient environment and uses this to characterize the particles in terms of both size and shape parameters. Analyses are carried out at peak particle throughput rates of up to 10,000 particles per second, and semiquantitative data relating to the size and shape (or more correctly asymmetry) spectra of the sampled particles are provided to the user via a graphical display which is refreshed or updated at 5-s intervals. In addition to the real-time display of data, continuous data recording allows subsequent replay of measurements at either normal or high speed. Preliminary experimental results are given for aerosols of both spherical and nonspherical particle types, and these suggest the instrument may find use in environmental monitoring of aerosols or clouds where some real-time semiquantitative assessment of particulate size and shape spectra may be desirable as an aid to characterizing the aerosol and its constituent particulate species.

Potential for recognition of airborne asbestos fibres from spatial laser scattering profiles

This Short Communication describes some preliminary results of research which seeks to develop a method by which individual airborne asbestos fibres may be detected in real-time within a contaminated environment. The method proposes using an analysis of the spatial laser scattering profile (i.e. the complex manner in which individual particles scatter laser light), recorded from individual airborne particles, as a means of classifying the particles in terms of their morphological characteristics. Scattering profiles have been recorded from both crocidolite and chrysotile fibres and these display differentiating features which suggest that in certain cases it may be possible to discriminate each type of fibre from other airborne particulates. Examples of scattering profiles are presented and methods of automated pattern recognition, which are currently under development, are briefly discussed.

A real-time monitoring system for airborne particle shape and size analysis

Original article can be found at: http://www.agu.org/journals/jd/ Copyright American Geophysical Union. DOI: 10.1029/96JD00228 [Full text of this article is not available in the UHRA]

20 P 20 Complementary techniques for the analysis of the shape of airborne particles

J. M. Clark, P. H. Kaye, E. Hirst and K. Reid, ‘Complementary techniques for the analysis of the shape of airborne particles’, Proceedings of the 1993 European Aerosol Conference, 4-8 October 1993, Journal of Aerosol Science, Vol 24 Supplement 1, 1993, pp. S243-S244, published by Elsevier Ltd, Copyright