Carnwath Bid For Environmental TestingRESOLUTION NO. 2004-277
RESOLUTION AWARDING BID FOR ENVIRONMENTAL TESTING
AT CARNWATH FARMS
At the regular meeting of the Town Board of the Town of Wappinger, Dutchess
County, New York, held at Town Hall, 20 Middlebush Road, Wappingers Falls, New
York, on the 23rd day of September, 2004, at 6:00 P.M.
The meeting was called to order by Joseph Ruggiero, Supervisor, and upon roll
being called, the following were present:
PRESENT: Supervisor -
Councilmember-
ABSENT:
Joseph Ruggiero.
Robert L. Valdati
Maureen McCarthy
Vincent Bettina
Joseph Paoloni
The following Resolution was introduced by Ms. McCarthy--: and seconded
by Mr. Valdati
WHEREAS, bids were received by Don Swartz, Architect to the Town of
Wappinger for environmental testing at Carnwath Farms, and
WHEREAS,. bid were received as follows:
Air Care Environmental Service $4,068
Quality Environmental Solutions and Technologies $4,407
WHEREAS Don Swartz of Cerniglia and Swartz, has provided an award
recommendation to the Town Board.
NOW, THEREFORE, BE IT RESOLVED,
1. The recitations above set forth are incorporated in this Resolution as if
fully set forth and adopted herein.
2. The bid for the environmental testing at Camwath Farms is hereby awarded
to Quality Environmental Solutions and Technologies for an amount not to
exceed Four Thousand, Four Hundred and Seven Dollars ($4,407) in
accordance with the award recommendation letter dated September 17, 2004
from Don Swartz of Cerniglia and Swartz, to the Town Board.
3. Supervisor Joseph Ruggiero is hereby authorized and directed to execute
said Contract on behalf of the Town of Wappinger.
The foregoing was put to a vote which resulted as follows:
JOSEPH RUGGIERO, Supervisor
Voting Aye___
ROBERT L. VALDATI, Councilmember
Voting Aye
VINCENT F. BETTINA, Councilmember
Voting Absent
JOSEPH P. PAOLONI, Councilmember
Voting Absent
MAUREEN MCCARTHY, Councilmember Voting Aye
Dated: Wappingers Falls, New York
September 23, 2004
The Resolution is hereby duly declared adopted.
Caw11A�5WA-tot
ARCHITECTS, PLANNERS AND INTERIOR DESIGNERS; P.C.
September 17, 2004
Town of Wappinger
20 Middlebush Road
P.Q. Box 324
Wappingers Falls, N.Y., 12590
ATTN: HON. JOSEPH RUGGIERO
SUPERVISOR
RE: CARNWATH FARMS
ENVIRONMENTAL TESTING
Dear Joe;
Attached please find two proposals from two testing companies for environmental testing at Carnwath
Farms. At the Town's request we requested pricing for testing several- areas of future work such as the roof
of the main building and the Carriage House .gutter system, and additional pricing for testing the air quality at
the main building interior and the Chapel interior:
The Base Proposal addresses the environmental testing at the main building roof and fascia/soffit system
Re -roofing them
.ain building will require rernoving-the old roof flashings and repairing the fascia system
prior. to installing the new roofing material. Thus, environmental testing will focus on the flashings. (asbestos)
and the wood fascia, soffit and ornamental trim (lead paint).
Alternate # 1. entails environmental testing -at the r=n building interior. rooms which are utilized for events
by the Town of Wappingers. The. Vestibule and'three adjacent rooms will be tested for air quality, which
based on site observations will involve environmental 'testing -for asbestos in the plaster and environmental
testing for mold which is evident on. several surfaces withimthe indicated spaces. Humiditystudies will -also
be conducted as part of the air qualitytesting.
Alternate # 2 entails testing the Carriage House gutter system flashings (asbestos) and the surfaces of the
gutter system (lead paint). In order to minimize water penetrationinto the building, the glitter system is going
to be removed and stored for future use:
Proposal # 1 from Quality Environmental Solutions &Technologies, Inc. (QuES&I) proposes -a sum of
$1600 for the base scope of work at the main building roof. Alternate # 1 for the main building and Chapel
interior is for $1982 and 'Alte nate # Zfor the Carriage House gutter system is for $825. The total price from
QuEs&T for all the environmental testing, which includes the two alternates is $4407.
Proposal # 2 from Air -Care Environmental Services, Inc, (A(tS) proposes a sum of $1945 for -the base
scope of work at the main building roof. Alternate #.1 for the main building and Chapel interior is for $1543
and Alternate # 2 for the Carriage House gutter system is for $580. The total price from ACES for all the
environmental testing, which includes the two alternates is $4068.
134 ACADEMY STREET POUGHKEEPSIE NEW YORK 12601- 4312
Tel: (845) 473-.0204 Fax: (845) 473-0284 www.csarchite.cts.com
September 17, 2004
Town of Wappinger
RE: CARNWATH FARMS
ENVIRONMENTAL TESTING
Page 2
ACES has also -proposed testing paint chips in lieu of utilizing NRF equipment. For paint chip sampling
ACAS has proposed $895 for. the Base scope, $1957 for Alternate # 1 and $670 for Alternate # 2, for a total
cost of $3522. It should be noted that NRF technology offers immediate results as opposed to paint chips
which must be sent to a lab. initially paint chips would cost less than xMF equipment, however, should more
areas be required to be tested, paint chip sampling would -entail additional cost for each paint chip sample
taken, whereas XRF equipment provides a fixed cost for immediate results from. many areas. We recommend
utilizing XRF technology, which would afford the Town flexibility at the time of testing to conduct more
extensive testing at numerous "areas at a fixed cost
Based on our review of the two proposals, we recommend awarding the testing work to QuES&T..Although
their price is $4407 as compared to $4068 for ACES, QuES&T comes recommended by the Dutchess
County Department of Public Works for which they have don_ a testing before. QuES&T is also a local firm
with an office located on Route 9 in Wappingers Falls.
If you have any questions, please feet free to call us at our office. Thank You.
Sincerely,
CERNIGLIA & SWARTz
AR HITECTS, PLANNERS AND INTERIOR DESIGNERS, P.C. .
Aonald L. Swartz R.A
Partner
cc: file: Ietter\Proposal5unmm .wpd
QuES&T
Quality Environmental Solutions & Technologieg, Inc,
September 14, 2004
Mr. Joseph Rugsicro
ne Town of Wappingers'
20 Middlrbush Road
PO Box 324
Wappingers Falls, NY 12590
Re: Camwarth Farms Environmental Testing
Dear i&. Ruggiero,
Quality Environmental Solutions & Technologies, I= is pleased to submit a proposal to perform
a limited inspection and report of suspected asbestos containing, lead containing materials, and retold at
the Carnwarth Farms, in Wappingers Falls, NY as follows:
• The roof mea, facia and soffit will be inspected for asbestos and lead containing materials on
the Main Building exterior.
+ In the Maim Building first floor foyer and three adjoining rooms the plaster will be tested for
asbestos content and lead based paint. The painted woodwork and trim will be tested for iced
based paint. QuES&T will collect Sparc trap air saint plcs for presumptive Fungal ID and
enumeration and visible growth will be swabbc4 for viable Fungal. ID and en=eradon. A
humidity study will be performed utilizing a OnywolflAQ Mcter.
•
The chapel area plaster will be tested for asbestos Content and lead based paint.
The carriage house exterior gutter system will be inspected to identify asbestos containing
materials and lead based paint.
The inspection will include a visual inspection, review of existing docutncnmtion, representative,
sampling of suspect Mbestos Canudning Materials, analysis ofbomagcnous paints, and preparation of a
report summarizing the results a C the itwpccdons and sample analysis throughout the arca cf inspection as
outlined above.
QaS&'T' looks forward to working with The Town ofwappingcrs in the cnviroumental
consulting area, If we can be o rany additional assistance or for additional information concerning any of
our services, please contact US at (845) 2956031.
Sincerely,
Lawrcncc Holzaprel
Director, Field Opct dons
1376 Rote 9. Wappingers Fulls, New York 12590 ' Vb. (845) 298.6031 • a (84$) 2913-6251 'P www.QuaIhycnv Cam
Proposal V0-2$7
Prafessiond Smvjcc*t
PRICING PROPOSAL
ENVIlkONJVM, NTAL TESTING
CARNNWARTFF FARMS
QuES&T agrees to provide the :!following scmices;
AsbestaR Tns ection
+ Collection And analysis of suspect friable material using PLM protocol.
• Collection and analysis of suspect Dan -friable material using QTEX protocol.
• Discussion of laboratory results for all bulk samples (PLN4/QTipA).
• Docum=ation of all analytical laboratory certifications.
• Preparation of a final report identifying eatimatcd quantity, loeatioa, typc4, and condition of
ACM.
I F Lead -Based Paint Survey
XRI` technology sampling of all homogenous painted surfvccs.
+ Sequential and summary reports of all Surfaces tested.
• Prepamtion of a final report summarizing lead based paint identified.
TAStudv
• Spore trap -dr samples for presumptive rungal ID and enumeration.
+ Bulk swabs for viable fungi identification and enumcmdon.
* Humidity study utilizing GraywolfIAQ monitor.
ENvIRONMMNTnL CONSULTi1NG ANA TRAININC
Page 2 oro
Propasal IFPD4-287
Professional Services
LUMP SUM PRrc, NG PROPOSAL
Buse Scone:
Muin Building Roof
labor (2 merit 1 day) S 640
QTEM Bulk Sample Analysis** S 540
W Lquipmcnt Fcc $ ISO
Report $ 250
Misc. Materials $__2_2
Total $1,600
Alternate I
Main Building/Chapel Interior
Labor
Included in Base Scope
PLM Bulk Sample Analysiw a**
$ 192
XRF Equspmcnt Fee
Tnei uded in Buse Scope
Spore Traps*
$ g00
Fungal ID Bulk*
S 540
Humidity Study
S 450
Report
Included in 13asc Scope
Misc. Materws
Includ in Base Scope
Totem
$ 1,982
Alternate 2:
Carriage Rouse
Labor (2 mcts,h day) $ 400
QTEM Bulk Samplc Analysis** $ 405
XRI; lrquipmcnt Fcc Included in Base Scope
Misc. Materials 20
Total $ 825
* Sample Analysis ba.�cd on a 7 to 10 day turnaround, ** Bulk Sample Analy jz g prices based on 3 to 5
day turnaround, (prices may vary if client rcqucsts fisster sample analysis turnaround).
ACCEPTANCE OF PROPOSAL
To execute this agreement, please review, sign, date. & fax to (845) 298-6031.
The Town of'Wanpinve":
By
Signature print Name & Title Data
ENVIRONMNTAT, CONSULTING AND TRAINING
Page 3 of 4
Proposal 004-217
Professional Services
"Standard of Care/Warranty for Mold. The Pnrties'agtcc and uudcr ttund that die presence ofmold and the
evolving Undcrstanding of risks which may be ag8ociated with human exposure to certain types of mold represent an
area of medical, scl=tLric and indm ry knowledge which is only beginning to mature and that this area of
knowledge at present is, at best, incomplete. Thcrcfora, as a fundamental incentive to Qu>rS&T t4 undertake the
provision of services to Client, Client agrees that QUM&T will be deemed to have fully complied with tiny
contractual standards of performance or any legal mandate ofnon negligcatbchaviorbyproviding Qul:S&Ts
Services comristrnt with the proposed Scope cf Services, Tire parties agree and understand that mold is mobile, - It
can arise in new places and recur in Bectu+ which have been rcmcdiatcd dttc to water intrusion events and proccr.mcs
beyond the control of QuMT. Accordingly, QuES&T is not liable for such new or recurring mold growths.
Further, due to the microscopic nature of mold spores, it is agreed and und=%ttood that na warraffD, nr nr mr ve that
all -mold hese been Uenti red ar remov . 'e gtade or intended by uF4& TAssessnsents ai'watar lrtttiisinp or
accumulation risk by QuES&T, if Any. 4= not to be understood as a complcto list ofpotential wnys in which water
intrusion or ucctumulation may occur at the Sitc(s) subject to this AgrccmenG NO OTHER lVARRAN•I'y,
EXP ESS OR IMFI rZD, IS MriDF. OR EVTEND VD HER.6BYAND AATAND ALL OTHF—R SVCx
I-VARRA117.MY ARE JTF.REBYFULLYAND COMFLCTF,I,YDISCLAIMF� By Quzu "
Acknowledgement of Limitations and Disclaimer ( j Initial
Client roeogt L=v and agrees that mold can occur In new locations or can rer ccur In ltaewrionv where It hay been
removed due to lunttatianx in derecdon or removal merhadv (spares are microscopic), limitations in time and.e=4
Mew and mod fed orpreviously unknown water intention and/or accumulation events. Client ftrrrhe'r recogni:etl. the
unsettled liabllity environment surrau#ding mord Therefore, as a fundamental Inducement to Quality
Environmental Solutiorty & Tecltnotogles Inc (QuF,S�7). to undertake the Work dr.,s dhed In rite Scope of
Services, Client hereby agrees to iMernn fy, defend and !told harmless QUESdT its joint ventures, of liala . parent
and subsidiary eneWty and the employees, oJicers, directony, represetttativcc and agents of Qu,ESIT, and'all of the
foregoing fram and against any and all claim4 suits, caalco of actions, liabilities, costs (Including bur not limited to
reasonable attorney'i ferx) and judgmenri which are based in whole or in par? upon (or which wound in) mold.
based liublli% txccpt to rare extent of the sole negligence of &ZU7' and the other lndemnitcex ,cet out immediately
precedln& but subject alwow to the Limitation of I.lablllty set out elsewhere herein. "
TJta Par tiex agree and understand that the presence of mold and rite evolving understanding of riAs which may be
associated with human ,vpoxtrra to eeertaln types of mold repro vent an arca of medical, selentific and industry
knowledge which Ix only beginning to mature and that this area of knowledge at prezent ix, at hart, Incomplete.
7 crefore, as a fundamental incentive to QuZYa7' to undertake the provision of cervices to Client, Client agrees
that Q118YAT spill be deemed to have f ally complied lvith any contrachtal standards of performances or any legal
mandate ofnon-negligent behavior by providing QuBMAT .T services consistent with the propoxed Scope of Services,
The p'artles agree and unde7 viand rhat mold is mobile. it can arise in now places and recur In are= which have
beers' remediated date to water Intrusion events and procaxes beyond the control of QuF.SA7', Accordingly,
QuFaAT Is not liable for such new or recurring mold grouchy. Purrher, due to rhe microscopic nature of mold
spora ,. it iv agreed and understood that QLy_CmO,
ed
made gr (llfit tiled by QuMIT, Aysm=cno ofwarer lntruslan or accumulation rink by QuZYt7,, If anv, are not to
be understood ax a complete 111t ofpotendal ►nays in which water, intnixion or accumulation may occur at the She(s)
xubjeat to rhis Agreement. NO OTIIER MARRAN7 r. F,XFRF.SS OR IMn=. , ISHADE OR IN EADED IIEABY
AM ANY AJVD AU dMER SUCFI TVARRANTIESARCIIERR'BYFUZI.YAND COMPLE7TELYDISCr�41 .D BY
QuES,�T.
LWMON1V ENTAL CONSUIMNG AND TRMrNING
Pagc 4 of 4
u1/ L1/ LVV'-1 LV. pro 1 (It3Ll r (0n7 t1uWz:)Uua PAGE U2
September 16, 2004
Joseph Ruggiero - Supervisor
Town of Wappinger
20 Middlebush Road
Wappingers Fells NY 12SQ0
RE: Camwath Farms
Environmental Testing
Dear Joseph Ruggiero,
Air Care Environnnntai Service
330 Nassau Blvd
Mineola, NY 71601
Tel. 516 739-2331
Fax. 516 746-4002
Air Care Environmental Service Inc. (ACES) is pleased to subunit a proposal to pefform a
limited inspection and report of suspect Asbestos Containing materials, Load containing
materials, and mold at Carriwath Farms in Wappingers Falls, N -Y-, as follows;
The roof area, fascla and soffd will! be inspected for asbestos and lead containing Materials
on the main building exterior. In the main building first floor foyer and 3 adjoining rooms the
Plaster will be bested for asbestos content and lead based pak*
ACES will collect SpprO trap air samples fpr prOsuaWfive fungal ID and enumeration- Visible
growth will be swabbed for viable Fungal ID and enumeration.
A humidity study will be performed utilizing a Greywolf 1AQ meter or an equivalent piece of
equipment.
The Chapel area pia tOr will be tested for asbestos content and lead based paint content,
The Carriage House exterior gutter system will be inspected to identify asbestos containing
material and lead Ease paint.
The inswffan will include a visual inspection, and review of existing document that have
been made ava�kble to us_ RspreaeMeth a sampling of suspect ACM, analysts of
homogenous paw, and preparation of a report summarizing the results of the inspections
and sample analysis ftwoughout the area of inspection as outlined above -
All sampling and Analysis procedures will be conducted within Federal, Slate and local
regulations.
Attached you vA fmd a bread 6mm of the estimated cost for this project.
The total estimate using a XRF msct*m is $4oW
The total estimate using hint chips sampling is $3522
If you have questions about this or any other situation please dao root hesitate to call us at
(516) 739-2331
in ,
;r�
#rick Cuascut
u1! 4lE cc!uw Lci. Yo 1 (ItsZI e e!DUJ I:UAtD1-;UI
LUMPS M PR -WING PRO .AL
Base scare
Main Buildin Roof
Labor
QTEM Bulk Sample Analysis
X (Equipment Fee
*(Paint Clip Sample Analysis)
Report
Misc. Material
Total $1945
*Total 5895
AhMW—C #1
Main BWft9/Chanel Intexzar
Labor
PLM Bulk Sample Analysis
XRF Equipment Fee
*(Paint Chip Sample Analysis)
Spare Traps
Fungal ID Bulk
Humidity Study
Report
Misc. Material
Total $1543
*Toro! $.1957
Alternate #2
Carriage House
Labor
QTEM Bulk Sample Analysis
XRI+' Equipment Fee
*(Paint Chip Sample Analysis)
Misc. Material
Tota! $580
*Total $670$670
$320
$420
$1050
$126
$ 40
$115
$320
$240
included in fee above
5414
$420
$325
$100
$40
$98
6 samples
7 samples
12 samples
23 samples
6 samples
5 samples
$160
$420 6 samples
included in fee above
$90 5 samples
included in ;fee above
PAGE 63
September 15, 2004
RE: CARNWATH FARMS
ENVIRONMENTAL TESTING DEFINITIONS
QTEM Qualitative Transmission Electron Microscop
Analysis by machine that identifies characteristics of structures (non -friable)
using light refraction. Has to do with Asbestos, for fiberglass, asbestos, etc.
PLM Polarized Light Microscopy
Has to do with Asbestos, for friables like sheetrock, plaster, joint compound, etc.
XRF X -Ray Fluorescents Analyzer
Has to do with Lead Faints
Spore Trap Has to do with Mold, part of air quality, indicates if something is airborne.
Bulk Swabs Has to do with Mold, indicates what strain it is.
Industrial Health 2001, 39, 39-50
Review Article
Measurement of Airborne Fibers: A Review
Paul A. BARON
Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Cincinnati,
OH 45226 USA
Received January 19, 2001 and accepted January 29, 2001
Abstract: Current fiber measurement techniques arose primarily due to health concerns over asbestos
exposure. Fiber toxicity appears to be primarily a function of fiber concentration, dimensions and
durability in the lungs. There are two basic approaches to fiber measurement. Fibers can be collected
on filters and counted or analyzed by light or electron microscopy; alternatively, fibers can be detected
directly using a combination of fiber alignment and light scattering techniques. All of these
measurement approaches work best when the fibers are simple rod -shaped particles. However,
most fibers can exist as curved rods, complex bundles of fibrils, and agglomerates of fibers and
compact particles. These non -ideal shapes contribute to measurement bias and variability.
Key words. Asbestos, Chrystotile, Glass fibers, Fiber measurement, Fiber classification, Microscopy,
Direct -reading instrument
Introduction
Historically, fiber -related research primarily grew out of
health andmanufacturing issues regarding asbestos. Avariety
of mineral fiber types, especially asbestos, have been used
as commercial products for thermal or acoustic insulation,
and for reinforcement, especially in high temperature
materials such as friction products (e.g., brake linings, clutch
linings). In addition, fibers have been found as contaminants
of other minerals.
An interesting history of asbestos production is given by
Selikoff and Lee'), with indications of asbestos use in the
first century AD and perhaps earlier. Commercial production
of asbestos began in the mid -1850s in Europe and peaked
in the US in the early 1970s when health concerns over
asbestos exposure caused a large-scale shift to alternative
materials. Commercial production in several countries still
continues at high Ievels, with Russia, Canada, and China
being the highest producers. Total production in 1999 was
1.79 million metric tons').
Asbestos -associated disease was noted as far back as
Roman times, but the first careful documentation of lung
disease due to asbestos exposure reported in the literature
was credited to Cooke). Reports of asbestos-related disease
continued up to the 1960s and 1970s, when larger scale
studies documented the extent and seriousness of the health
effects. Some of these include reports by Selikoff et ak'),
Nakamura'), and McDonald).
The three primary diseases associated with asbestos
exposure are asbestosis, the result of inflammation and
collagen formation in lung tissue; lung cancer; and
mesothelioma, an otherwise rare form of cancer associated
with the lining around the lungs. A current theory describing
the toxicity of fibers indicates that fiber dose, fiber dimension,
and fiber durability in lung fluid are the three primary factors
determining fiber toxicity'). The dose, or number of fibers
deposited in the lungs, is clearly an important factor in
determining the likelihood of disease. Both fiber diameter
and length are important in the deposition of fibers in the
lungs and how Iong they are likely to remain in the lungs.
Figure 1 indicates some of the factors that determine fiber
deposition and removal in the lungs. Fiber length is thought
to be important because the macrophages that normally
remove particles from the lungs cannot engulf fibers having
40
Air Deposition Mechanisms:
Flow -Settling
-Impaction
-interception
-Diffusion
Btonchlole ' i -Electrostatic Attraction
hick Fiber Deposition
(Impaction at carina)
Bifurcation
In Fiber Deposition
Alveoli EZY (Diffuslo
n)
Removal Mechanisms:
-Clllary Escalator
-Dissolution
-Macrophage Engulfment
Fig. 1. Schematic of mechanisms that determine fiber deposition
and retention in the lungs.
lengths greater than the macrophage diameter. Thus, longer
fibers are more likely to remain in the lungs for an extended
period of time. The macrophages die in the process of trying
to engulf the fibers and release inflammatory cytokines into
the lungs'). Fiber diameter is also important because fiber
aerodynamic behavior indicates that only small diameter
fibers are likely to reach into and deposit in the airways of
the lungs. The smaller the fiber diameter, the greater its
likelihood of reaching the gas exchange regions. Finally,
fibers that dissolve in Iung fluid in a matter of weeks or
months, such as certain glass fibers, appear to be somewhat
less toxic than more insoluble fibers. The surface properties
of fibers are also thought to have an effect on toxicity.
Asbestos is one of the most widely studied toxic materials
and there are many symposia dedicated to and reviews of
its behavior in humans and animals', 9-17).
A variety of techniques were used for asbestos
measurement up until the late 1960s12). Earlier than this, it
was not widely recognized thatthe fibrous nature of asbestos
was intimately related to its toxicity, so many techniques
involved collection of airborne particles and counting all
large particles at low magnification by optical microscopy.
Thermal precipitators, impactors (konimeters), impingers,
and electrostatic precipitators were all used to sample
asbestos. Perhaps the primary technique in the US and UK
during this early period was the liquid impinger, in which
particles of dust larger than about 1 fort aerodynamic diameter
were sampled at 2.7 I/min and impacted into a liquid reservoir.
After sampling, an aliquot of the liquid was placed on a
slide in a special cell, particles larger than 5 pm size were
PA BARON
counted, and the results were reported in millions of particles
per cubic foot. Dissatisfaction with this approach stemmed
from lack of correlation with fiber concentration and disease
in the workplace. Various indices of exposure have been
developed that attempt to relate a portion of the fiber size
distribution to the toxic effects. Some suggestions regarding
the appropriate indices for each of the asbestos related
diseases were suggested by Lippmann").
Fiber Dimensions
Fibers are particles that have one dimension significantly
larger than the other two. Fibers are often characterized or
selected according to their aspect ratio, the ratio of the large
dimension to one of the short dimensions. If no other criteria
are used, then materials that might not normally be considered
fibrous may contain a fraction of particles that meet the
criteria for fibers. The distribution of fiber dimensions can
usually be characterized by assuming a cylindrical geometry,
i.e., the two small dimensions are identical, and measuring
the length and diameter of individual fibers. The distribution
of fiber sizes generated by grinding bulk material or by
mechanically releasing particles into the air often results in
a two-dimensional (bivariate) lognormal distribution. Such
a distribution is characterized by five parameters: the
geometric mean length, the geometric mean diameter, the
length and diameter geometric standard deviations, and a
correlation term that relates length to diameter14). In addition,
various other parameters that are a function of length and
diameter, such as aerodynamic diameter, can also be
characterized by a lognormal distribution").
Most of the discussion here assumes that fibers are straight
objects that can be well defined by several parameters.
However, many real-world particles are not so simple to
describe. In fact, the detailed features of many fibers can
aid in their identification. Fibers are often curved or otherwise
misshapen. Compact particles are frequently attached to
fibers, affecting their aerodynamic behavior. Asbestos
mineral is composed of fibrils (about 0.03 pm diameter)
that are packed together. When the mineral is broken apart
mechanically, the material separates primarily between fibrils
and the resulting fibers are usually bundles of fibrils. The
ends of the fibers can be broken apart, with smaller bundles
or individual fibrils spread apart, yet still part of the fiber.
In addition, multiple fibers and compact particles can be
held together as complex structures. The complexity of fiber
shapes affects all of the measurement and separation
techniques described below and frequently makes it difficult
to compare one method to another.
Industrial Health 2001, 39, 39-50
MEASUREMENT OF AIRBORNE FIBERS: AREVIEW
In addition to asbestos fibers, there is a wide range of
fibrous materials being produced for commercial purposes.
These include fibrous glass, mineral wool, refractory ceramic
fibers, wood and other plant fibers, and synthetic organic
fibers. Most of these fibers tend to have larger diameters
than asbestos fibers. Carbon nanotubes (<5 nm diameter)
have recently been produced in small-scale commercial
quantities and because of their high tensile strength, high
conductivity, and other special properties, show great promise
as a commercial material'). Measurement techniques must
be tailored to the size distribution and physicochemical
properties of the fibers.
This review is limited to measurement of fibers in air.
There are a variety of techniques that address concentration
of asbestos and other fibers inbulkmaterial andmeasurement
of mass concentration of fibers.
Light Microscope Counting
As asbestos -induced disease became widely studied in
the 1960s, cellulose -based membrane filter sampling was
applied to asbestos sampling in combination with high
magnification phase contrast light microscopy (PCM) for
counting fibers. This technique involved collection of fibers
uniformly over the surface of a cellulose ester filter, placing
the filter on a microscope slide and making it transparent,
and observing the fibers in the sample with a high
magnification (-450X) phase contrast lightmicroscope. Over
the years since then a great deal of research has been carried
out to improve and standardize the method. Walton discussed
many aspects of this technique in a journal review issue').
The high variability of the analysis results and the method's
dependence on operator technique made this research
difficult. The method does not detect all fibers because of
the limitations of light microscopy, so that the method is
only an index of exposure, with the assumption that what is
detected is correlated with the fibers actually causing disease.
This should be remembered when considering some of the
parameters discussed below. The aim of evaluating changes
to the PCM technique may depend on whether consistency
with other laboratories within a country or throughout the
world is more important than making measurements that
are more closely related to health effects. Anumber ofinethod
factors have been investigated, including:
41
and coworkers investigated 1250x magnification to improve
fiber detectability, but this has not been adopted in any
established methods"). Pang also investigated the effect of
using lower magnification (400x) and found that counts were
lower for chrysotile asbestos by 25%, but that amosite fiber
counts were unaffected").
Phase contrast optics: This contrast enhancement
technique allows detection of asbestos fibers down in the
range of about 0.25 ym diameter, depending on fiber type.
Other techniques such as dark field microscopy may offer
improved detectability, but also increase the background due
to non-fibrous particles.
Test slide to check optics: A test slide was developed to
allow a check of proper alignment and magnification in the
microscope". This ensures a reasonable level of uniformity
in microscope setup and operation. Improper setup can
reduce detectability of fibers. There have also been cases
where the optics were "too good," and higher than acceptable
counts resulted.
Counting area in microscope field: Some early
measurements with the phase contrast microscope were made
using a rectangular graticule for defining the counting area,
while others were made using the entire microscope viewing
area. It was found that larger viewing areas resulted in lower
counts, so a graticule was developed that gave a 100 µm
diameter counting area in each microscope. This has been
standardized in all current methods. Figure 2 contains the
Walton -Beckett graticule21) with examples of how fibers are
counted.
,Sample preparation techniques
Filter type: Virtually all measurements are made using
0.8,um pore size mixed cellulose ester (MCE) filters. Some
measurements are made using 1.2µm pore size filters when
sampling low concentrations to allow higher flow rate through
the filter. Smaller pore size filters are used to ensure that
fibers are deposited as near the surface of the filters as
possible. This results in fibers ending up in the same plane
so that they can be readily viewed with a minimum change
of focus during fiber counting.
Selection of the liquid for making filter transparent: A
liquid is placed on the filter that closely matches the filter
refractive index, yet has an index that is as far as possible
from that of the fibers being detected. Rooker et al. showed
that refractive index difference between cleared filter and•
Microscope -related parameters fibers translated directly into detectability of small diameter
Microscope magnification: The exact level of microscope fibers'). A viscous solution of dimethyl phthalate and diethyl
.magnification depends on microscope design, but most oxalate mixed with cellulose filter material was .commonly.
current methods use 450x (± 10%) total magnification. Pang used in the 1970s and early 1980s, However, it did not result
12'D
5
gsxan
�Ox3
�0
s
�3
1. . 1 fiber 8_ 1 fiber. Ignore overlong pa llcle.
2. 2 fibers 7. 112fiber.
3. 1 fiber. Note diameter makes A non- 8. 0 fitter. Both ends out of field.
thoracic g. 0 fiber. Outof field
4. 1 fiber
S. 0 fibers. Too short
Fig. 2. Sketch of the Walton -Beckett graticule'" that is used to de-
fine the counting area and aid in selecting fibers to be counted in a
phase contrast light microscope.
The counting rules listed are those used in NIOSH Method 74001L1.
in a permanent sample, with crystallization of the mount
and movement of fibers often occurring several days after
sample preparation. Permanent slides were needed for quality
assurance purposes and the sample preparation technique
was also slow and required some skill. A rapid acetone -
based filter clearing technique was developed that could be
used safely in field situations231. After clearing, filters were
coated with triacetin to surround the fibers. This resulted
in a longer lasting sample (typically several years) and is
currently specified in most methods. Another technique uses
a resin called Euparal to surround the fibers and results in a
permanent slide preparation241.
Filter loading: The number of fibers on the filter is usually
specified to be within a certain loading range to ensure
consistent counting. Cherrie et at. demonstrated using a
serial dilution technique that counting efficiency was a
function of concentration of fibers on the filter"). At very
low filter loadings (<100 fiber/mm2) there was a tendency
to count high relative to an intermediate range of
concentrations (100-1300 fibers/mm2), This "overcounting"
was apparently due to greater visibility of fibers in a clean
visual field. This effect was noted for both human counters
and an image analysis system. At high filter loadings (>1300
fibers/mmz), undercounting occurred due to overlap of fibers
with other fibers and with compact particles. Most published
methods: indicate that optimum counting occurs within the
100-1300 fibers/mm2 range, while some restrict the range
PA BARON
further to Iess than 650 fibers/mm2.
Fiber counting rules: The basic fiber counting rules for
most current methods indicate that fibers longer than 5 ,um
with an aspect ratio greater than 3:1 should be counted. These
rales were selected because shorter fibers were difficult to
detect by optical microscopy and the 3:1 aspect ratio was
used to discriminate between fibrous and non-fibrous
particles. There has been a great deal of controversy over
these rules. The use of a longer fiber cutoff, e.g., 15-20
,um, has been suggested, based on two separate arguments:
first, that most asbestos fibers are relatively long and thin
and the longer fiber cutoff would discriminate better toward
fibers that were truly asbestos fibers according to
mineralogical definitions; and second, that fibers that enter
the lungs are removed readily by macrophages if they are
shorter than about 15 ym. Longer fibers cannot readily be
engulfed by macrophages, thus staying in the lungs for a
long period and causing continuing fibrosis.
Other aspects of fiber counting have been investigated,
including how to count non-standard fiber shapes,
overlapping fibers, overlapping compact particles on fibers,
and bundles of fibers. Each of these factors can have a
noticeable effect on the final count. Cowie and Crawford
investigated the effect of some of these factors and estimated
most of them made a difference in the final count on the
order of 2002'). Many ofthe methods currently in use have
slight variations in their interpretation of which fibers to
count and thus can contribute to variation in results between
countries and organizations.
Quality assurance schemes
Sample recounts: Most methods require individual
counters to recount about 10% of the field samples to ensure
consistent counting procedures and alert the analyst in the
case of problem samples. In addition, it is recommended
that counters have samples that are routinely recounted to
ensure consistent counting within a laboratory over time.
Interlaboratory sample exchanges: Crawford et al. found
that use of sample exchange programs were more important
in ensuring agreement between laboratories than similarity
in details of the counting rules"). Thus, exchange of field
samples between laboratories is commonly performed to
improve consistency of counting. A description of several
quality assurance techniques for asbestos fiber counting is
described by Abell et al."').
Quality check samples: In order to get agreement between
laboratories within a country or internationally, several
programs send- out -identical ..samples to participating;::
laboratories to assess their relative performance 19,31) . These
Industrial Health 2001, 39, 39--50
MEASUREMENT OF AIRBORNE FIBERS: AREVIEW
43
programs provide feedback, often tied to laboratory fraction of the fibers were misidentified as multiple fibers,
accreditation, that provides incentive for laboratories to not detected at all and groups of compact particles or edges
ensure that their performance is similar to that of other of large particles were detected as fibers").
laboratories.
Several methods using optical microscopy have been
published by national's- :) and internationa?'- 35) organizations.
Most countries have methods very similar to the ones
referenced here.
In addition to simply counting the fibers, there are
techniques available for providing at least tentative
identification of fiber type. Fiber shape can be used to limit
the type of fiber present. For instance, glass fibers tend to
be straighter, with smoother sides than chrysotile fibers.
Polarizing light techniques can also be used to identify larger
diameter (> 1 pm) fibers. These are based on the optical
properties of the materials, including refractive index and
crystallinity. These techniques can provide quite positive
identification for the presence of certain types of fibers, but
are limited for airborne fibers because they only work for
the larger diameter fibers. These techniques are often used
in analysis of bulk materials').
Image Analysis
Since fiber counting by human analysts produces relatively
high biases and variability, several researchers haveattempted
to develop automated counting systems. With the increases
in computer power over the last 25 years, it has been tempting
to assume that fiber counting is a solvable problem and
significant efforts have been made to develop such a system.
The most intensive effort to produce a fiber counting system
was carried out by Manchester University in collaboration
with the Health and Safety Executive in the UK37j. The
Manchester Asbestos. Program (MAP) was able to give
reasonably good agreement with human counters for certain
types of samples. It was used as a reference analyst for the
Inoue and coworkers have developed image analysis
software using a microprocessor -based PC"). Initial tests
indicate that it works approximately as well as' human
counters. Inoue also evaluated how well human counters
and the image analyzer did in detecting the same fibers in a
sample and found that only about 50% of the fibers were
consistently counted by all counters, so the image analysis
system did approximately as well as the human counters401
Further testing of the image analysis system is needed.
In addition to image analysis, optical microscopy can be
enhanced using a personal computer to more easily observe
the image and to mark and measure fiber dimensions, with
automatic recording of the fibers counted"). This does not
appear to affect the counting accuracy since the analyst still
decides which fibers are to be counted.
Scanning Electron Microscopy
Scanning electron microscopy (SEM) has not been the
focus of as much method development as either light
microscopy or transmission electron microscopy (TEM).
PCM found favor because of the low equipment cost and
lower training level required for analysis. TEM is preferred
for environmental and research studies because it offers the
highest resolution and the most positive identification
capabilities, allowing visibility of all asbestos fibers, and
electron diffraction for crystal structure identification and
energy dispersive x-ray analysis for elemental measurement.
SEM has intermediate resolution, with many instruments
of this type not able to. see all asbestos fibers. However,
many modern SEMS have the capability of detecting asbestos
fibrils. Energy dispersive x-ray analysis is also available
for many SEMS, providing some qualitative information of
US and UK reference sample programs for several years. fiber type. However, since electron diffraction cannot be
Eventually, the MAP was dropped as the reference because performed by SEM, this often leaves open the question of
it was not sufficiently consistent for all types of samples. positive identification of fibers.
The principle problems with image analysis of asbestos Particles are observed in the SEM when abeam of electrons
fibers include: the complexity of many fiber shapes, including is focussed onto the sample surface and scanned over an
bundles, agglomerates, and split fibers; the fibers often go area. The electrons are scattered from the surface and detected
in and out of the plane of focus; the background includes above the surface synchronously with the beam scan rate
many particles and other non-fibrous shapes; the phase and an image of the scanned surface is created. Thus, the
contrast optics produces haloes around particles in the sample SEM measures the surface of particles on a substrate. The
that can be detected as fibers; and finally, and perhaps most best image can be obtained on conducting objects deposited
importantly, the contrast between the fibers and background on a smooth, conducting substrate. Particles are often
is poor- and many fibers are near the -detection threshold. - - -deposited-on aluminurn or carbon -planchets that fit -directly
An evaluation of the MAP program indicated that a significant into the SEM or onto polycarbonate membrane (track -etched,
44
Nuclepore) filters. The samples are usually coated with gold
or carbon to increase conductivity.
There have been some SEM methods developed for fiber
counting'). These methods are primarily used for inorganic
man-made fibers that have larger diameter fibers than can
occur with asbestos. Thus, all the fibers are potentially visible
using the SEM.
Transmission Electron Microscopy
The transmission election microscope (TEM) is considered
the most powerful technique for counting and analyzing
fibers. It is capable of detecting the smallest fibers (carbon
nanotubes and asbestos fibrils) and can be used to determine
crystal structure from electron diffraction as well as
determining elemental composition from energy dispersive
x-ray analysis. Although TEM analysis is potentially very
powerful and accurate, the process of sample collection and
preparation and details involved in sample analysis can
degrade the quantitative accuracy of the technique. Several
other, more specialized techniques have been used for
analyzing particles and can also be applied to fibere ).
Airborne fiber samples for TEM analysis are typically
collected onto a filter, usually a polycarbonate membrane
or MCE membrane filter. For the latter filter type, the filter
is chemically collapsed to form a smooth upper surface on
which collected fibers are trapped. Sometimes the surface
is etched using a low temperature asher to expose the fibers
collected on or near the surface of the original filter. The
filter is coated with a carbon film that entraps fibers exposed
on the filter surface and the filter material is then dissolved
away. The carbon film is transferred to a TEM grid (usually
3 mm diameter) and the sample can be placed in the TEM
for analysis.
The above approach to preparing MCE filters for TEM
analysis is called the direct -transfer approach, since fibers
are transferred to the carbon film with minimum disturbance
to the way they were collected. An alternative technique is
to dissolve the entire filter in liquid, ultrasonicate the
suspension to disperse the particles, and deposit an aliquot
of the particle suspension onto a polycarbonate filter for
final transfer to the carbon film. This is called the indirect
transfer technique. With the indirect technique, the optimum
particle loading of the TEM sample can be obtained and
soluble particles can be removed from the sample. However,
the suspension process can change the apparent size
distribution of the particles and fibers by breaking apart
agglomerates or even.breaking:apart asbestos fibers into
smaller fibers or fibrils"). The breakup problem can be
PA BARON
especially severe for chrysotile.
The process of sample collection and preparation is a
complex one that can introduce biases into the final
measurement. Since only small portions of the filter are
measured when analyzing by TEM, sampled fibers that
deposit non -uniformly onto the filter due to inertial,
gravitational and electrostatic effects, will be measured
inaccurately47). Fibers that penetrate the filter surface and
are not transferred to the carbon film will be lost. If the
filter is incompletely dissolved away from the carbon film,
the sample will be difficult to analyze.
Many of the sources of bias and variability noted in
sampling and counting by PCM also apply to TEM analysis.
Fiber counting in a TEM can also introduce biases and
variability in the final result. There is a tendency to use the
high magnification of the TEM to look for the smallest fibers,
while ignoring some of the larger ones. Even so, fibers shorter
than 0.5 fun tend to be missed because they are difficult to
see in the background clutter of the sample48>. Carter et al.
foundthat TEM counting gave poorer precision than counting
the same sample by PCM49).
There are several established methods for analyzing fibers,
especially asbestos fibers, by TEM50-54>
Optical Detection
Two types of light scattering detectors are commonly used
for measuring airborne dust concentrations: the optical
particle counter (OPQ, which detects and counts individual
particles and the photometer (sometimes called a
nephelometer) that detects the scattering from all particles
in a defined detection volume. A standard OPC was used to
detect asbestos concentrations in a workplace where the
aerosol was primarily fibrous and good correlation with fiber
counts was obtained"). A nephelometer may also be used,
but is less likely to indicate fiber concentration, especially
when non-fibrous dusts are present.
Light scattering from single, well-defined fibers has formed
the basis of several fiber detection techniques. If a fiber is
perpendicular to the axis of illumination, the scattered light
is concentrated into a plane containing the illuminating light
axis and perpendicular to the long axis of the fiber.
The width of the scattered light plane has been shown to
be related to fiber length"). A number of instruments have
been developed that use the unique light scattering pattern
from fibers. In order to take advantage of this property of
fibers, the fibers must be aligned perpendicular to the
illumination .. alas: ;,
Several alignment techniques have been applied to fibers.
Industrial Health 2001, 39, 39-50
MEASUREMENT OF AIRBORNE FIBERS: AREVIEW
Timbrell investigated the magnetic alignment properties of
fibers and found that many asbestos fibers aligned- either
parallel or perpendicular to the magnetic field"). He applied
the field to fibers collected on a filter and suspended from
the surface of the filter in a liquid"). When the liquid dried,
the fibers remained aligned on the cleared filter surface. The
scattering intensity and pattern from the filter surface could
then be related to fiber type and concentration. A commercial
instrument was developed using this approach, but was not
successful because the scattering intensity depended too much
on fiber type and could not be readily correlated with fiber
counts for a variety of samples").
When a sufficiently conductive fiber is placed in an electric
field, the fiber will polarize and align parallel to the electric
field. The conductivity of the fiber does not have to be very
high since the alignment only requires moving a few electrons
several micrometers along the length of the.fiber. Thus,
asbestos is quite conductive on this basis, even though it is
normally considered an insulator. Glass fibers are
intrinsically non-conductive, though at high enoughhumidity
levels (about 50% RH), the water adsorbed on the surface
provides enough conductivity to allow electrostatic
alignment. The fibrous aerosol monitor (Model FM -7400,
MIE, Inc. BedfordMA) was developedusing the electrostatic
alignment technique and applies a field that aligns and rotates
individual fibers in a laser beam. This allows specific
detection of fibersfi0) and may even be used to measure fiber
length")
Fibers will align parallel to the flow direction in a gradient
flow field. Thus, laminar flow through. a tube can be used
to establish aparabolic flow profile (Poiseuille flow). Fibers
will align with their long axis very nearly parallel to the
tube axis64, though the fibers will periodically flip 180053).
An instrument was developed using flow alignment of fibers
and electrostatic deposition, with optical scattering detection
of the deposited particles"). Although promising, the
instrument was not commercialized. Hirst and coworkers
developed an instrument coupled with a neural network
algorithm to identify light scattering patterns from flow -
aligned fibers, but this instrument also was not
commercialized"). Figure 3 shows scattering patterns from
12 ,um long SiO2 micromachined fibers. Sachweh and
coworkers used a similar instrument with multiple angle
scattering detection for laboratory studiesb6). Another device
that uses flow alignment and multiangle scattering detection
is commercially available (FibreCheck, Casella, Bedford
UK). A field comparison of the FibreCheck and the FM -
7400 measuring.man-made mineral and chrysotilefibers-
indicated that both. instruments tended to underestimate fiber
U
0.5
0
0.1
5 0.05
c
0
0
0.01
E
$ .0.005
ag
0,001
45
0.2 0.4 1 2 4 10 20 40
Production Nominal Fiber Size - pm
Fig. 3. Relationship between measured average exposures, ex-
pressed as fiberslce (determined by phase contrast microscopy), and
nominal diameter of fiber manufactured (Copyright American In-
dustrial Hygiene Association).
concentration compared to phase contrast microscope
counting67). Although the correlation between all these
methods was good for man-made mineral fibers, the
FibreCheck had especially poor detection capability for small
diameter chrysotile fibers.
Optical techniques can easily detect well -formed > 1 ym
diameter fibers. When curved or more complex fibers are
detected, these methods may become less efficient. Since
fiber detection instruments are usually compared with the
filter collection/PCM counting method, it can be difficult
to calibrate such an instrument for all types and sizes of
fibers.
Fiber Separation by Diameter
The aerodynamic diameter of fibers is dependent primarily
on fiber physical diameter and fiber density, with a minor
dependence on fiber length"). Several -devices have been
used to measure or separate fibers by diameter. A spiral
centrifuge was used to separate fibers and reference spherical
particles•to.estimate=fiber. aerodynamic diameter69). It was.
found that the aerodynamic diameter was directly
46
Fig. 4.
(a) Experimental scattering profile recorded from a signal 12,im
silicon dioxide fire (image capture in 2 ,1s).
The horizontal scattering implies close alignment of the particle with
the vertical sample airflow.
(b) Experimental scattering profile recorded from a single 12 lim
silicon dioxide fiber (image capture in 2 ps).
In this case the conic section form of the scattering implies a particle
orientation approximately 10° clockwise to the vertical in the plane
orthogonal to the laser beam axis, and 15° tilted forward (towards the
laser) in the plane of the beam axis .(Reprinted from J Aerosol Sci 23,
Kaye, PH, Hirst E, Clark, 7, and Micheli, F. Airborne particle shape and
size classification from spatial light scattering profiles. 597-611
Copyright (1992) with permission of Elsevier Science).
proportional to physical diameter, proportional to the square
root of the fiber density, and proportional to fiber length to
the 116' power. For mineral fibers having a density of about -
3 g/cm3, the aerodynamic diameter was approximately three
to five times the physical diameter of the fiber. Behavior of
glass fibers in a cascade impactor -was investigated by Burke
and Esmen"). A small correction to the aerodynamic diameter
PA BARON
was developed to take into account interception of longer
fibers with the impaction surface. An inertial spectrometer
was used to measure fiber aerodynamic diameter and good
diameter separation was achieved"),
As with most airborne dusts, fiber settling will reduce
the number of larger diameter fibers in a distribution as the
distance from the source ofthe dust increases. Esmen showed
that average fiber concentration in workplaces decreased
exponentially with an increase of fiber diameter, indicating
that the larger diameter fibers settled out more quickly than
smaller diameter fibers (Fig. 4)1>. Cyclones, impactors and
Porous foam classifiers were evaluated for efficiency of
removing airborne fibers not likely to deposit in the 1ungs131.
Fiber Separation by Length
Since the health effects of fibers are strongly correlated
with fiber length, there have been many efforts to separate
fibers by length. These efforts included bulk separation
techniques and aerosol separation techniques. Spumy used
a liquid sedimentation technique that provided some length
classification and also suggested that sonic generation could
provide size -classified aerosol"). A proprietary liquid
suspension separation technique was used for an inhalation
toxicity study"), Hanton et al. found that by compressing
glass fibers at high pressure, the fibers could be broken to
give a length mode in the 1020 ym range").
Myojo described a technique for classification of airborne
fibers by passing them through sieves". This allowed
measurement of the fiber length distribution. However, the
technique did not provide high resolution and was limited
in output because of particle loading on the sieves.
Chen et al. electrically charged monodisperse -diameter
carbon fibers and separated them by length in a mobility
analyzer78l. Chen indicated that the separation was achieved
by a combination ofthe charging and electrophoresis process.
Lipowiez suggested that this separation technique -was
effective because the fibers were being separated by
dielectrophoresis") and provided the theory for a
dielectrophoresis-based classifier8°1. Baron and coworkers
developed such a classifier (schematic in Fig. 5) and were
able to obtain length distributions with standard deviations
of about 10-20%81.821. This classifier separated fibers by
placing them in a gradient electric field, which polarized
the fibers, aligned them parallel to the electric field, and
caused them to drift toward the higher field electrode. The
drift velocity was proportional to the fiber length squared.
.This classifier was used.•taprovide small quantities: (up to l
mg per day) of monodisperse -length material for toxicity
Industrial Health 2001, 39, 39-50
MEASUREMENT OF AIRBORNE FIBERS: A REVIEW
Clean art sheath flown Annular aerosol region
Outer Inner i
Longer fibers deposit
firrd on central cylinder
Fibers attracted to
central cylinder
Shorter fibers
deposit last
axElh�mp 'low
*" eYttscts
hors fibers
and compact
particles
High Voltage Classified flbera exiting In sheath
air near central cylinder
Fig. 5. Schematic of dielectrophoresis classifier showing the sheath
and input and output aerosol flows.
Fiber motion toward the inner electrode is caused by induced polarization
of the fibers and the higher field closer to the inner electrode. The inner
electrode is coated with oil to prevent resuspension. An ac electric field
is used to reduce deposition ofparticles with a net charge.
assay0•117. It was also demonstrated that the dielectrophoresis
classifier could be used to measure bivariate fiber
distributions. when combined with an aerodynamic sizing
instrument such as the Aerosizer (TSI, Inc. Minneapolis)s4).
The instrument is not commercially available and is difficult
to scale up for production of larger quantities of fibers.
Conclusions
The capability for measurement of fiber size distributions
is available through microscopy and to a much lesser extent,
through direct -reading instrumentation. The traditional
methods of microscopy are relatively inaccurate when
compared to many chemical analysis methods because of
the many sources of error in the sampling and analysis
procedure. Further work is needed in automating fiber
counting through improved image analysis of microscope
images and through improved direct -reading instrumentation.
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