Third Edition
†Deceased.
This third edition first published 2022
© 2022 John Wiley & Sons, Inc.
Edition History
John Wiley & Sons, Inc. (1e, 1982)
John Wiley & Sons, Inc. (2e, 1999)
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Library of Congress Cataloging‐in‐Publication Data Applied for:
ISBN: 9781119494041
Cover Design: Wiley
Airborne particles are present throughout our environment. They come in many different forms, such as dust, fume, mist, smoke, smog, or fog. These aerosols affect visibility, climate, and our health and quality of life. This book covers the properties, behavior, and measurement of aerosols.
This is a basic textbook for people engaged in industrial hygiene, air pollution control, radiation protection, or environmental science who must, in the practice of their profession, measure, evaluate, or control airborne particles. It is written at a level suitable for professionals, graduate students, or advanced undergraduates. It assumes that the student has a good background in chemistry and physics and understands the concepts of calculus. Although not written for aerosol scientists, it will be useful to them in their experimental work and will serve as an introduction to the field for students starting such careers. Decisions on what topics to include were based on their relevance to the practical application of aerosol science, which includes an understanding of the physical and chemical principles that underlie the behavior of aerosols and the instruments used to measure them.
Although this book emphasizes physical rather than mathematical analysis, an important aspect of aerosol technology is the quantitative description of aerosol behavior. To this end I have included 150 problems, grouped at the end of each chapter. They are an important tool for learning how to apply the information presented in the book. Because of the practical orientation of the book and the intrinsic variability of aerosol properties and measurements, correction factors and errors of less than 5 percent have generally been ignored and only two or three significant figures presented in the tables.
Aerosol scientists have long been aware of the need for a better basic understanding of the properties and behavior of aerosols among applied professionals. In writing this book, I have attempted to fill this need, as well as the long‐standing need for a suitable text for students in these disciplines. The book evolved from class notes prepared during nine years of teaching a required one‐semester course on aerosol technology for graduate students in the Department of Environmental Health Sciences at Harvard University School of Public Health.
Chapters are arranged in the order in which they are covered in class, starting with simple mechanics and progressing to more complicated subjects. Particle statistics is delayed until the student has a preliminary understanding of aerosol properties and can appreciate the need for the involved statistical characterization. Applications are discussed in each chapter after the principles have been presented. The more complicated applications, such as filtration and respiratory deposition, are introduced as soon as the underlying principles have been covered. The operating principles of different types of aerosol measuring instruments are given in general terms so that one may correctly interpret data from them and explain the frequent differences in results between instruments. Discussion of specific instruments is limited because they change rapidly and are covered well in Air Sampling Instruments, 5th edition, ACGIH, Cincinnati, OH (1978). The latter (or any future edition) makes an excellent companion to this text. Several general references are given at the end of each chapter. Tables and graphs are provided in the appendix for general reference and for help in dealing with the problems at the end of each chapter.
While many people have contributed to this book, I would like to acknowledge particularly Klaus Willeke of the University of Cincinnati, who reviewed the manuscript and made many helpful suggestions; Kenneth Martin, who provided the SEM photos; and Laurie Cassel, who helped prepare and type the manuscript.
William C. Hinds
Boston, Massachusetts
February 1982
More than 16 years have passed since the first edition of Aerosol Technology was published in 1982. During this time the field of aerosol science and technology has expanded greatly, both in technology and in the number of scientists involved. When the first edition was published there were two national aerosol research associations, now there are 11 with regular national and international meetings. Growth areas include the use of aerosols in high‐technology material processing and the administration of therapeutic drugs, and there is an increased awareness of bioaerosols, aerosol contamination in microelectronic manufacturing, and the effect of aerosols on global climate. While the first edition proved to be popular and useful, and became a standard textbook in the field, changes in technology and growth of the field have created the need to update and expand the book.
The objective of the book has remained the same: to provide a clear, understandable, and useful introduction to the science and technology of aerosols for environmental professionals, graduate students, and advanced undergraduates. In keeping with changes in the field, this edition uses dual units, with SI units as the primary units and cgs units as secondary units. Besides updating and revising old material, I have added a new chapter on bioaerosols and new sections on resuspension, transport losses, respiratory deposition models, and fractal characterization of particles. The chapter on atmospheric aerosols has been expanded to include sections on background aerosols, urban aerosols, and global effects. There are 26 new examples and 30 new problems. The latest edition of Air Sampling Instruments remains an excellent companion book, as does Aerosol Measurement, by Willeke and Baron. Both provide greater depth and detail on measurement methods and instruments.
Of the many people who have helped with this edition, I would like to particularly acknowledge Janet Macher, Robert Phalen, and John Valiulis for reviewing specific chapters; Rachel Kim and Vi Huynh for typing manuscript changes; doctoral student Nani Kadrichu for entering the equations; and finally, my wife Lynda for her continued support during this long process.
William C. Hinds
Los Angeles, California
More than 22 years have passed since the publication in 1999 of the second edition of Aerosol Technology. During this time the field of aerosol science and technology has continued to grow in both size and technology. There are now 18 national aerosol research associations compared to 11 when the second edition was first published. While the first and second editions were popular and became standard textbooks in the field, the continued growth of the field and its technology have created the need to update and revise the book.
The objective of the book continues to be the same; to provide a clear, understandable, and useful introduction to the science and technology of aerosols for environmental professionals, graduate students, and advanced undergraduates. We have continued the use of dual units, SI and cgs. We have included newer findings in atmospheric aerosols and bioaerosols, and expanded the contents of sampling methods and instruments in various chapters.
We would especially like to thank the following for their help in producing this third edition: Dr. Yan Lin and Yuening Guo. Finally we would like to thank our respective spouses, Lynda and Yuqing Zhang for their continued support through this process.
William C. Hinds
Yifang Zhu
Alamo, California
Los Angeles, California
| a | acceleration, particle radius |
| ac | centrifugal acceleration, Eq. 3.15 |
| A | area, cross‐sectional area |
| Ap | cross‐sectional area of a particle |
| As | surface area |
| b | coefficient for Hatch—Choate equation, Eq. 4.47 |
| B | particle mobility, Eq. 3.16 |
| B0 | luminance of an object, Eq. 16.26 |
| B′ | luminance of background, Eq. 16.26 |
| c | molecular velocity; velocity of light |
 |
mean molecular velocity, Eq. 2.22; mean thermal velocity of a particle, Eq. 7.10 |
| crms | root mean square molecular velocity, Eq. 2.18; root mean square thermal velocity of a particle, Eq. 7.9 |
| cx, cy, cz | velocity in the x, y, z directions |
| C | particle concentration in sampling probe |
| Cc | Cunningham correction factor, Eq. 3.19; slip correction factor, Eq. 3.20 |
| CD | drag coefficient, Eq. 3.4 |
| cm | mass concentration, mass of particles per unit volume of aerosol |
| CMD | count median diameter |
| CN | number concentration, number of particles per unit volume of aerosol |
| CR | apparent contrast, reduced contrast, Eqs. 16.27 and 16.33 |
| C0 | true concentration, inherent contrast, Eq. 16.26 |
| CER | collection efficiency for respirable precollector, Eq. 11.14 |
| CET | collection efficiency for thoracic precollector, Eq. 11.18 |
| d | particle diameter; derivative |
 |
arithmetic mean diameter, Eq. 4.11 |
| d* | Kelvin diameter, Eq. 13.5 |
| da | aerodynamic diameter, Eq. 3.26 |
| dA | specified average diameter, Eq. 4.47 |
| dc | diameter of cylinder |
| dd | droplet diameter |
| de | equivalent volume diameter, Eqs. 3.23 and 19.3 |
| df | fiber diameter |
| dF | Feret's diameter, Fig. 20.1 |
| dg | geometric mean diameter, Eq. 4.14 |
| di | midpoint diameter of the ith group |
| dm | diameter of a gas molecule |
 |
diameter of average mass, Eq. 4.19 |
| dmm | mass mean diameter, Eq. 4.26 |
| dM | Martin's diameter, Fig. 20.1 |
| dp | particle diameter |
 |
diameter of average property proportional to dp, Eq. 4.22 |
| dPA | projected‐area diameter, Fig. 20.1 |
 |
p moment average of the qth moment distribution, Eq. 4.36 |
| ds | Stokes diameter, Eq. 3.26 |
 |
diameter average surface, Eq. 4.22 |
| dsm | surface mean diameter, Eqs. 4.27 and 4.31 |
| dt | tube diameter |
 |
diameter of average volume, Eq. 4.22 |
| dw | wire diameter |
| d50 | particle diameter for 50% collection efficiency, Eqs. 5.28 and 19.1 |
| D | particle diffusion coefficient, Eqs. 7.1 and 7.7 |
| Dba | diffusion coefficient of gas b in air, Eq. 2.35 |
| DF | fractal dimension, Eq. 20.5 |
| Dj | impactor jet diameter |
| Ds | sampling probe diameter |
| Dv | diffusion coefficient of vapor in air |
| D0 | duct diameter |
| DF | deposition fraction, total, Eq. 11.5 |
| DFAL | deposition fraction, alveolar, Eq. 11.4 |
| DFHA | deposition fraction, head airways, Eq. 11.1 |
| DFTB | deposition fraction, tracheobronchial, Eq. 11.3 |
| e | charge of an electron; coefficient of restitution, Eq. 6.6; base for natural logarithms |
| E | efficiency; electrical field strength, Eqs. 15.6 and 15.10 |
| E | overall filter efficiency, Eqs. 9.1 and 9.2 |
| ED | single‐fiber efficiency for diffusion, Eq. 9.27 |
| EDR | single‐fiber efficiency for diffusion‐interception interaction, Eq. 9.28 |
| EG | single‐fiber efficiency for settling, Eq. 9.30 |
| EI | impactor efficiency, Eq. 5.27; single‐fiber efficiency for impaction, Eq. 9.24 |
| EL | surface field limit, Eq. 15.28 |
| Eq | single‐fiber efficiency for electrostatic attraction, Eq. 9.32 |
| ER | single‐fiber efficiency for interception, Eq. 9.21 |
| EΣ | total single‐fiber efficiency, Eqs. 9.14 and 9.33 |
| f | fraction; frequency; frequency of light, fraction of sites with colonies, Eq. 19.3 |
| fab | fraction between sizes a and b |
| f(dp) | frequency function of particle size distribution, Eq. 4.4 |
| fn | fraction of particles having n charges, Eqs. 15.30 and 15.31 |
| F | force |
| F(a) | cumulative frequency at a, Eq. 4.8 |
| F(x) | cumulative fraction at x, Eq. 11.12 |
| Fadh | force of adhesion, Eqs. 6.1–6.4 |
| FD | drag force, Eqs. 3.4 and 3.8 |
| FE | electrical force, Eq. 15.8 |
| Ff | frictional force on a fluid element, Eq. 2.36 |
| FG | force of gravity, Eq. 3.11 |
| FI | inertial force on a fluid element, Eq. 2.39 |
| Fn | form component of Stokes drag, Eq. 3.6 |
| Fth | thermal force, Eqs. 8.1 and 8.4 |
| Fv | volume fraction of spheres in liquid, Eq. 21.6 |
| Fτ | frictional component of Stokes drag, Eq. 3.7 |
| g | acceleration of gravity |
| G | gravitational settling parameter, Eq. 9.29; ratio of cloud velocity to particle velocity, Eqs. 17.6 and 17.7 |
| GSD | geometric standard deviation, σg, Eq. 4.40 |
| h | height; velocity head, Eq. 2.43 |
| H | height of chamber; thermophoretic coefficient, Eq. 8.5; latent heat of evaporation of a liquid |
| i1 | Mie intensity parameter for perpendicular component of scattered light, Eqs. 16.23 and 16.24 |
| i2 | Mie intensity parameter for parallel component of scattered light, Eqs. 16.23 and 16.25 |
| I | number of intervals for grouped size data, Eq. 4.14; light intensity, Eq. 16.7 |
| I0 | incident light intensity, Eq. 16.7 |
| I1(θ) | intensity of scattered light at angle θ, perpendicular polarization, Eq. 16.24 |
| I2(θ) | intensity of scattered light at angle θ, parallel polarization, Eq. 16.25 |
| IF | inhalable fraction, Eq. 11.7, 11.8 |
| IFN | inhalable fraction for nose breathing, Eq. 11.9 |
| J | diffusion flux, Eqs. 2.30 and 7.1 |
| k | Boltzmann's constant |
| kv | thermal conductivity of a gas or vapor |
| K | a constant; corrected coagulation coefficient, Eq. 12.13 |
| K0 | uncorrected coagulation coefficient, Eq. 12.9 |
 |
effective coagulation coefficient for polydisperse aerosols, Eq. 12.17 |
| KE | electrostatic constant of proportionality (SI units), Eq. 15.1 and Table 15.1 |
| KE | kinetic energy |
| Kn | Knudsen number = 2λ/dp |
| Ku | Kuwabara hydrodynamic factor, Eq. 9.22 |
| KR | Kelvin ratio, Eq. 13.5 |
| Kst | Pressure rise index, Eq. 18.1 |
| K1,2 | coagulation coefficient of particle size 1 with size 2, Eq. 12.16 |
| L | length; length of fluid element, length of chamber, duct, or tube; path length of light beam, Eq. 16.7 |
| LR | limit of resolution, Eq. 20.9 |
| LV | visual range, Eq. 16.35 |
| m | mass of molecule; mass of particle; index of refraction, Eq. 16.2 |
| mr | relative index of refraction, Eq. 16.5 |
| M | molecular weight; total mass |
| MMD | mass median diameter |
| n | number of molecules per unit volume; number concentration; number of elementary charges |
| nA | number concentration at A |
| nc | rate of capture, Eq. 12.20; number of organisms collected, Eq. 19.3 |
| ni | number of particles in the ith group |
| nL | charge limit, Eqs. 15.28 and 15.29 |
| nm | number of moles |
| n(t) | number of charges at time t, Eqs. 15.24, 15.25, and 15.33 |
| nz | rate of molecular collisions, Eq. 2.24 |
| n0 | initial number concentration; initial number of charges |
| N | number of molecules; total number of particles in sample; particle number concentration |
| Na | Avogadro's number |
| NA | numerical aperture, Eq. 20.8 |
| Ni | ion concentration |
| N(t) | particle number concentration at time t, Eq. 12.12 |
| N0 | particle number concentration at time zero |
| p | pressure; partial pressure |
| PA | partial pressure of component A, Eq. 13.1 |
| Pd | partial pressure of vapor at droplet surface, Eq. 13.5 |
| Ps | saturation vapor pressure, Eq. 13.2 |
| PT | total pressure |
| Pv | velocity pressure, Eqs. 2.43 and 2.44 |
| P∞ | partial pressure of vapor away from droplet |
| P | pressure, perimeter |
| P | penetration, overall filter penetration, Eqs. 9.3 and 9.4 |
| Pe | Peclet number, Eq. 9.26 |
| PF | PM10 fraction, Eq. 11.19 |
| P(n) | probability of n solid spheres in a droplet, Eq. 21.5 |
| q | amount of charge; amount of charge on a particle, Eq. 15.2; weighting parameter for moment distributions |
| qF | filter quality, Eq. 9.12 |
| qMD | median of the qth moment distribution, Eq. 4.48 |
| Q | flow rate |
| Qa | absorption efficiency, Eq. 16.10 |
| Qe | extinction efficiency, Eq. 16.8 |
| Qs | sample flow rate; scattering efficiency, Eq. 16.10 |
| Q0 | duct flow rate |
| r | radial position |
| R | gas constant, Eq. 2.1; radius; interception parameter, Eq. 9.20; separation distance of electric charges, Eq. 15.2 |
| Re | Reynolds number, particle or flow, Eq. 2.41 |
| Ref | fiber Reynolds number, Eq. 9.13 |
| Re0 | initial Reynolds number, Eq. 5.21 |
| RF | respirable fraction, Eq. 11.10 |
| S | stopping distance, Eq. 5.19 |
| SR | saturation ratio, Eq. 13.3 |
| SMD | surface median diameter |
| Stk | Stokes number, Eqs. 5.23 and 5.24 |
| Stk50 | Stokes number for 50% collection efficiency, Eq. 5.28 |
| t | time; thickness of filter |
| T | temperature |
| Td | temperature at droplet surface |
| TF | thoracic fraction, Eq. 11.15 |
| T∞ | temperature away from droplet |
| U | velocity; gas velocity; gas velocity inside filter, Eq. 9.6; gas velocity in sampling probe |
 |
average velocity in duct |
| U0 | face velocity of filter; free‐stream velocity |
| v | gas volume |
| vd | droplet volume |
| vp | particle volume |
| vm | volume of a molecule, Eq. 13.9 |
| v1, v2 | volume of gas or vapor at state 1 or 2 |
| V | velocity of particle; relative velocity between particle and gas |
| Vc | critical velocity for bounce, Eq. 6.5; cloud velocity, Eq. 17.4 |
| Vdep | deposition velocity, Eq. 7.27 |
| Vf | final velocity |
| VMD | volume median diameter |
| Vr | gas velocity in the r direction, Eq. 3.41 |
| V(t) | particle velocity at time t, Eq. 5.15 |
| Vth | thermophoretic velocity, Eqs. 8.2 and 8.6 |
| VT | tangential velocity, Eq. 3.15 |
| VTC | terminal centrifugal velocity, Eq. 3.14 |
| VTE | terminal electrical velocity, Eq. 15.15 |
| VTF | terminal velocity for constant external force F, Eq. 5.5 |
| VTS | terminal settling velocity, Eqs. 3.13 and 3.21 |
 |
average velocity in the x‐direction, Eq. 3.37 |
| V0 | initial velocity; velocity at time zero |
| V∞ | gas velocity far away from particle or fiber |
| Vθ | gas velocity in the θ direction, Eq. 3.42 |
| W | width of slot; voltage |
| x | separation distance; distance from wall |
 |
average number of spheres per droplet, Eq. 21.6 |
 |
average number of spheres in an MMD‐sized droplet, Eq. 21.7 |
| xrms | rms displacement of particle, Eq. 7.18; |
| x(t) | position of particle at time t, Eq. 5.18 |
| y | vertical distance |
| z | number of molecular collisions per unit area, Eq. 2.15 |
| Z | electrical mobility, Eq. 15.21 |
| Zi | ion mobility |
| α | volume fraction of fibers in a filter, solidity, Eq. 9.7; size parameter for light scattering, Eq. 16.6 |
| αv | volume shape factor, Eq. 20.2 |
| β | correction factor for coagulation coefficient, Eq. 12.13 |
| γ | surface tension; fraction captured per unit thickness of filter, Eqs. 9.11 and 9.19 |
| Γ | velocity gradient |
| δ | diffusion boundary‐layer thickness, Eq. 7.30 |
| ∂ | partial derivative |
| Δd | diameter interval |
| Δp | pressure drop, pressure differential, Eqs. 2.47, 2.52, and 9.36 |
| ∇T | temperature gradient |
| ε | relative permittivity (dielectric constant); threshold of brightness contrast, Eq. 16.34 |
| ε0 | permittivity of vacuum, Eq. 15.2 |
| η | viscosity, Eq. 2.26 |
| Θ | angle between flow direction and sampling probe |
| θ | scattering angle |
| λ | gas mean free path, Eq. 2.25; wavelength of light; step size, Eq. 20.5 |
| λp | particle mean free path, Eq. 7.11 |
| µ | deposition parameter for diffusion loss in tubes, Eqs. 7.28 and 7.33 |
| ρ | density of gas; density of particle |
| ρb | density of bulk material |
| ρc | density of cloud, Eq. 17.2 |
| ρg | density of gas |
| ρL | density of liquid |
| ρp | density of particle |
| ρ0 | standard density, 1000 kg/m3 [1.0 g/cm3] |
| σ | standard deviation, Eq. 4.38 |
| σa | absorption coefficient, Eq. 16.11 |
| σe | extinction coefficient, Eq. 16.7 |
| σg | geometric standard deviation, GSD, Eq. 4.40 |
| σs | scattering coefficient, Eq. 16.11 |
| τ | relaxation time, Eq. 5.3 |
| φ | bend angle, Eq. 10.17; Fuchs‐effect correction factor, Eq. 13.16 |
| χ | dynamic shape factor, Eq. 3.23 |
| ω | angular frequency, rotational velocity |