Document 6wDpMgjk4G8r3bmyBYawrzNXg
FILE NAME: Z,,
DATE: Apr 27 DOC#: ,
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UNITED STATES OEPARTMENT OF COMME~CE National Bureau of Standards
WUI'llng:on. D.C. cQ2~~
May 2, 1979
MEHDRANOUM FOR.~~l>ale Scott, CPSC
Attention: Cail Wyer
Through: William West, t\......,,\ \/ _..7
Deputy AID (Engineering Sciences)
From:
Walter G. Leight, Chie
Product Safety Technology iv s on
J~~ Sid Greenvald,
Product Safety Technology Division
r./~
.~ v~
Subj ect: Examination of Hair Dryers from ase
(07166 and '7167) for Asbestos
.:..
On March 26, 1979, the Consumer Product Safety Commission delivered t~o
hand-held bair dryers to NBS and requested an examination to answer the following questions:
Ql. Does the insulating liner surrounding the beater element contain asbestos fibers?
Al. Sc~apings from each dryer vere immediately examined by electron microscopy and vere found to be primarily cbrysotile asbestos.
Q2. Does tbe effluent air from the operating dryer
contain chrysotile asbestos fiber? (The switch
setting giving the highest air volume rate would be
used, since this vould maximize any possible
erosion from the surface of the liner material.) : .. ~ :=
Quantitative results vere not required. but it v~~~-~ f'"oo,.;
aresqbueestsotesdfitbharitlsth, eb.uin%delersa,ngoer oclfumanpys bdeetnecotteedd. s~;:?~=_~''-.; ,~, -, i]
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A2. Smail amounts of chrysotile asbestos vere detecteQ
- in the effluent from each of the hair dryers, some
eI
..
., .
in the respirable size range. However, similar
amounts and size distributions vere found on
control (blank) filters used to collect sampfes
without hair dryers.
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GI00072
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It should be noted that the results summarized in this memorandum and its attachments are:based on limited experiments with but two hair dryers, both of vhich were brand new at the initiation of this task. Obviously, results cannot be generalized for other devices, nor is it pos,ible to state at this juncture vbether degradation might occur in the course of time.
The results of the investigation are given in the attached two part memo report. The first part deals primarily with the methods used to sample the air from the two hair dryers. In addition, some brief experiments were run, noting the effect~ Rf temperature ou a typical insulating liner.
In the first sampling method used, only a very small percentage of the air coming from the hair dryer was captured by polycarbonate membrane filter. The remainder of the output escaped to the opeu air. This method was employed because of back pressure and overheating difficulties originally encountered in trying to develop a total air capture system.
Four air samples were taken in this manner, and sent to the Cas and Particulate Science Division (GPSD) for analysis.
In the second method, all of the hair dryer output was captured by a 20 X 25 em (8 X 10 inch) polystyrene filter. Four trials were run as
follows:
Trial
Dryer
Time
1
Sample A (17167)
4.5 hrs.
2
Sample B (07166)
4.5 hrs.
3
Blank
16.0 hrs.
4
Blank
4.0 hrl.
The tvo blanks were run, each in a slightly different manner, in order
to determine the asbestos background level. These would serve as the
control.
.
All four samples were sent to the GPS Division for analysis.
Throughout the air sampling procedure, every effort was made to keep the filters as free as possible from any outside contamination.
Gr00073
3
The second par:e"of this report deals with the results of the analysis made by scientists in the Gas and Particulate Science Division. The instrumentation involved both Scauning Elec~ron Microscopy (SEM) and Transmission Electron Microscopy (TEM). the !EM is considered superior for this investigation because of its ability to detect smaller fibrils due to its higher resolution capability.
Att.achments
cc: Y. Porter - CPSC S. ~arshaw - NBS J. Small - NBS S. Toner - NBS H. Rook. - OS J. Hodgeson - NBS
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G100074
REPORT ON HAIR DRYERS TEST METHOD DEVELOPMENT
Prepared by .-. Samuel D. Tauer, Div. 763
April 27, 1979
On March 26, 1979, two haud-held hair dryers were delivered by the Consume~ Product Safety Commission. These dryers were said to contain a thermal insulating material composed, at least in pa~t, of asbestos. -The insulation in question was a cylindrical sleeve of paper-like material inserted in the section of -the dryer barrel surrounding the heating element. NBS was requested to determine, if possible, whether asbestos fibers and/or fiber bundles are released from the insulating material and emitted into the air stream of the dryer during operation. In addition, estimates of the range of size of fibrils and bundles was desired~
For the purposes of this report, the two commercially available hair dryers are identified as Sample A (CPSC 07167) rated at 1200 watts, and Sample B (CPSC 07166) rated at 1000 watts. A third dryer, Sample C, produced by the manufacturer of Sample A, was obtained from the NBS Product Performance Engineering Division. These three dryers were sent to the NBS Fluid Engineering Division for measurements of the air flow capacity. These measurements were made using a Th~rmo-Systems Inc., Ionflo Meter, SIN 074, Range 0 - 150 cubic feet per minute
i). The results obtained at maximum air flow capacity were as follows: Sacple
A, 35.5 CFM; Sample B, 28.0 CFM, and Sample C, 25.0 CFM.
Insulating Material
There is some concern" that, during the life of a dryer, any binder present in the insulation might be decomposed by the heat generated during normal use, thus possibly leading to an increase in the number of fibers that might be released into the air stream. Consequently~ the insulating liner was removed from a new dryer identical to Sample C. When a piece of this material was subjected to a bunsen burner flame, charring occured immediately, indicating the presence of a binder. A few minutes of additional heating burned off ;he char, leaving the paper brittle and friable. A section of the insulation was dried to constant weight in a circulating air oven at l10C. After one hour the material exhibited a weight loss of O.~%and after an additional 0.5 hour at 110C, exhibited a total weight loss of 0.38%. The specimen was then placed in a circulating air oven for 4 hours at 300C. On removal, the material exhibited some slight discoloration, but no eYideoce of charring, and an additional weight loss of 2.78%. The specimen was reexposed for an additional 6 hours at 300C, after which time the total weight loss was 2.88%, based on the constant weight after conditioning at 110C. There was no apparent additional discoloration of the material. There was no apparent evidence that the insulation had become friable, a condition which might result in release of larger quantities of fibers with continued usage.
Thermal measurements were then conducted on Sample C, by placing a ~ ~rmocouple against the inner surface of the insulating material, and measuring ~he temperature rise during normal operation of the dryer, with the controls set
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G100075
-'
2
for ~ximum temperature and highest flow rate. The temperature of the insulation
surface did not exceed operation, for periods
38C, of up
achieved during the first 2 - 3 minutes to 30 minutes of continuous operation.
of When
the
,
dr ro
ye se
r
t
was t o SO
u
r -
n
ed 5S
o C
f
f o
t
v
e
th r
e th
s e
urface next
te 20
m -
per 30
atur sec
e o
o nd
f. s,
t
he an
d
i
n t
s.ul hen
at c
ion ool
e
s d
u
rfa to
c a
e m
rapid bient
l
y
temperature this dryer,
in approximately 10 minutes. Temperatures in the air stream of measured at random points just inside the protective grill, were
observed to be in the range of about 65 insulation used in this dryer were typical
80C. to the
It was concluded that. if the dryer industry, then thermal
decompositon of the binder due to dry haat alone was considered unlikely.
Test Method Development
were
Although several potential methods for collecting emitted considered, it appeared desirable to attempt to develop a
fiber,
sy~tem
if in
any. which
all clo
s
of ed
-
t s
h y
e st
air em
t
emit echn
te iq
d u
e
by th was
e e
dryer xpecte
p d
as to
s
ed mi
throug nimize
h p
a ot
filter ential
l
medium. oss of
r
e
Su sp
ch ira
a b
l
e
fibers and fiber bundles, and to provide a better assessment of the amount and
range of sizes of the fibers.
The NBS fiber filter
Gas and Particulate medium suitable for
Science Division (GPSD) provided a polystyrenecollecting respirable asbestos fiber and also
amenable to further sample preparation procedure required prior to analysis by
means of the electron microscope.
The
A new dryer, identical to Sample C, was used dryer vas attached to one end of a section of
in developing rigid, 2-inch
the test method. inside diameter
tube. A water-filled manometer was attached to the tube as a means any changes in the air flow capacity of the dryer that miZht result
of monitoring from the air
impinsinz on the filter medium. Since the techniqes required to prepare a sample
for the
the electron microscope are simplified first attempt simply involved coverinz
by use of a small collection filter, the open end of the tube with a piece
of the filter. 2
The is
available surface area case. back pressure in
of the filter was the tube, created
appr~tely 25.2cm2 by the l~ air flow
(3.9 rate
in ). In th through the filter,
caused
rapid
overheatinz
of
the
dryer
with
subsequent
activation of seconds. The
the thermal overload switch. This event occurred in about 7 - 8 test equipment was then modified to accept a larger filter. about
73.6 cm2 (11.4 in2) to some extent, the
in area. operating
Although the back pressure problem was alleviated time prior to activation of the thermal overload
switch filter
was increased by to about 171 cm2
only 6 - 8 (26.5 in2)
seconds. Further increase in the size of in area did not result in a significant
the
improvement in the attachment
the procedure. of a sectiou of
Additional modification of the equipment involved 2-inch tube on the downstream side of the filter;
a DC motor and fan assembly, removed sealed into the open eud of the tube
from a dryer in an effort
identical to induce
to Sample C, was a nezative pressure
on the downstream side of the pressure on the upstream side
filter of the
as a potential means of balancing filter. This did not result in a
the significant
improvement over the preceding methods. ~-ver motor/fan assembly also failed to
Substitution of vacuum pump for the solve the back pressure problem. Pa~t
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GI00076
3
the problem seemed to be due to the difficulty in obtaining air-tight seals
on the downstream side of the filter in this temporary set-up, and part
appeared to be due to the of a sufficient nature to
difficulty in achieving a off-set the pressure drop
do~tream
across the
air flow filter.
capacity
At this point, ~Drk tecporarily abandoned at
on the closed-system collection technique was
the request of crsc staff members, in favor of
a
different collection procedure. Stipulations vere made that by placing a filter in the air stream of the dryers, Samples
tests A and
be
a,
conducted in such a
manner that the portion no effect on the normal
of the emitted air impinging on the filter would air flow capacity of the dryers, i.e.,.vould not
have
result in any back The hair dryer vas
pressure on placed in a
the dryer. These tests vere conducted as hood capable of providing a positive flow
follovs. of
filtered air into approximately 60
the dryer intake vents. The dryer was pointed downward from the horizontal position. A filter holder, containing
a
polycarbonate such a manner
membrane that the
filter, vas placed filter surface vas
in the air stream of approximately normal
the dryer in to the direction
of to
air the
flow and about 3 cm from filter holder provided a
the end of the dryer pressure drop across
barrel. A vacuum pump attached the filter. The effective
collection area of the filter surface Dryers A and B were each operated for
was of the continuous
order of two-hour
5.0 cm2 (0.78.in2). periods, using membrane
filters with staff of the
a maximum pore size of CPS Division indicated
0.1 the
micrometer absence of
(~). When an analysis by any asbestos fiber, Sample
the A
was then operated for p~-e $i~e of O.S ~.
a
continuous
a-hour
period
using
a
membrane
filter
with
a
For
Developmental vork these-'procedures, a
vas then resumed on a closed-system collection technique. high speed air sampling fan equipped with a filter holder
was used. _ The sampling fan vas approximately 120 and 200 ClM.
reported to have The accompanying
ai~ flow capacities of filter holder required
a
nominal
8 x 10 inch piece of the polystyrene collecting area of 420 cm2 (65 in2).
filter, and After some
provides an preliminary
available surface tests vere conducted,
it vas manner
found that the sampling fan/filter combination could be that the back pressure problem, previously noted, could
used in such a be solved. Thus
the The
tests final
could be conducted with the test set-up is described as
dryer functioning in follovs: hair dryer
its normal use mode. - tube, manometer,
cover plate assecbly - filter and filter (operated from a variable transformer).
holder - a slotted tube-sampling fan See the accompanying figure. The hair
dryer dryer
was placed in the hood supplying filtered air. All to the slotted tube were sealed to provide a closed
components from the hair system. The slotted
tube between the filter holder and the fan vas critical to the success of this
technique. of drawing
When the fan vas operating more air ~hrough the filter
at the 120 CFM flow rate, it was capable than the air flow capacity of the dryer
alone. The slotted tube, downstream from the filter. alloved some the syst,m so that the negative pressure on the downstream side of
air the
to enter filter
approximately balanced the pressure caused by the air flow the upstream side of the filter. Coarse adjustment of the
rate size
of of
the the
dryer slot,
on
coupled allowed
w;hiethafiirnefloawdjursattme enthtrooufghthethefanfilstpeered tobybme ebaanlsanocfedthesovtahraiatbtlhee trnaengsaftoirvme er,
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G100077
4
pressure of water
on the downstream side of pressure greater that the
the filter was only of the positive pressure produced
order of 1 by the air
-
2 mm
flowing Samples
from the dryer. Subsequently, tests were conducted
A and B were;1ndividually subjected to 4.S hours of
on the dryers. continuous operation.
Control tests to determine the conducted. One of these tests
presence of acy background was conducted for a period
asbestos were of 16 houri.
also In this
test the dryer was replaced with an extension tube and a so that the air flow impinging on th. filter surface was
linear air flow intermediate to
meter, that
of Samples A and B. the cover plate was
The second not used so
test that
was the
conducted for four hours. In this.. test., entire available surface" of the filter
was exposed sent to the
to the flow of filtered air GPS Division for subsequent
emitted by the hood. All analyses for the possible
filters were presence of
asbestos.
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GI00078
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u.s. DEPARTMENT OF COMMERCE
NATI~ au,.u.u 0,. STANDARDS
W~IHGTON. D.c::. IOI.M
-' ... . REPORT OF ANALYSIS
of Electron Microscopy
on Lining Materials from Hair Dryers
and Filter Samples
Submitted by Sid Greenwald, Division 763
Laboratory Nos.:
Proj ect No. :
Requisition NO.:
Analysts
:
553 39024 - 39029 763-1411 763-0936 . . John A. Small and Eric B. Steel
Request: The laboratory was requested to analyze the lining material from two hair dryers and determine if the material contained asbestos. In addition, the laboratory was also requested to determine if eight filter samples, four polycarbonate and four polystyrene, contain asbestos and to qualitatively estimate fiber loading and fiber size for each sample.
Samole Preparation:
Lining material. Each dryer was disassembled, and a piece approximately S mm2 was removed from the insulating sheet. These pieces were placed in separate vials. Approximately 2S rnl of ethyl alcohol was added to each vial. The vials were sealed and shaken both by hand and ultrasonically for a period of about 10 minutes, in order to free some of the fibers from the piece of insulating sheet.
Next, 200 mesh Cu TEM grids coated with 10 nm carbon foils were dipped into the solutions. After drying, one grid from each sample was investigated with a transmission electron microscope (TEM). The TEM was operated at 125 kV accelerating potential.
Polycarbonate filters. The polycarbonate filters were coated with approximately 20 nm of carbon. After coating, two 5 mm2 portions were cut from each filter and placed in a Jaffewick washer. One of the S mm2 sections from each filter'was placed in the washer with the carbon side up; the other was placed with the carbon side down. Once the filter material was cleared, the grids were investigated with the TEM.
\
._...._.._._------_....._-- -_....-_...-. GI00081
Polystyrene filters. One-fourth of eac~ 8ft x 10" polystyrene filter was dissolved in approximately 500 ml of xylene. \~en the filter had completely dissolved, the solution was
filtered through a 0.2 urn polycarbonate filter, which was
backed with a teflon filter. After filtration, the filter was washed with an additional 2S ml of xylene and allowed to air dry.
Next, the filters were carbon coated, and a S mm2 portion of each fil~~r was removed for scanning electron microscopy (5EM) analysis. The remainder of the filter was prepared on a TEM grid with a condensation washer. The grids were then
analyzed at 125 xV with the TEM. There was no evidence of particle loss due to the condensation washing.
The 5 mm2 portions removed for 5EM analysis were mounted
on aluminum stubs with double-sided tape and carbon coated
with approximately 10 nm of carbon. The 5tH was. operated at7.5 kV accelerating potential.
Resul ts: The samples used in the TEM were scanned at about ._ 5,000 to 20,000 times magnification for fibers. Those used in the SEM were scanned a't about l, 000 to 10,000 times magnification for fibers. Fiber identification was based on morphology and selected area electron diffraction in the TEH,
and morphology and energy-dispersive x-ray analysis in the 5EM. Detailed analyses were not done on all fibers. Representative
fibers from each sample were chosen at random for detailed
analysis, and the remaining fibers were identified by morphology only.
Lining material. The lining material was analyzed by TEM only. The results are shown in Figures 1 - 4. Figures 1 and 2 shOW fibers with the characteristic morphology associated
with chrysotile, very thin fibers (less than 50 nm wide) with hollOW tubes running down the center. Figures 3 and 4 are selected area electron qiffraction images of representative
fibers. These images show the slurring of the diffraction spots which is also characteristic of chrysotile.
Nuclepore filters.
Sample
1 2 3 4
Label
CP5C 7167, 8 hr. test, 0.8 urn filter CPSC 7167, 2 hr. test, 0.1 urn filter CPSC 7166, 2 hr. test, 0.1 urn filter CPSC 7167, 1 hr. test, 0.8 urn filter
The TEH and 5EM results from these filter samples were inconclusive . A few fibers were seen on the TEM and identified as chrysotile. However, there were not enough fibers present on any of the samples to conclude that the loading was above blank values.
Delbaq filters.
,Sample
5
6
7 8
Label
CPSC 7166, 4.5 hr. test CPSC 7167, 4.5 hr. test Blank for Background Asbestos, Blank for Background Asbestos,
16 hr. 4 hr.
test test
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GI00082
All the samples and blank~ showed the presence of small
amounts of chrysotile, the fiber loadinq on Samples 5 and 6
was not significantly hiqher than on Samples 7 and 8.
The results from the SEM analyses are shown in Figures
5 - 8. The x-ray spectra show that the fibers contain Mg
and Si. These two elements are the major constituents of chrysotile. In several of the fibers, however, the ratio of Mg to Si is, to a first approximation, higher than expected for chrysotile. This can be attributed to several factors such as the possibility of a binder material mixed with the chrysotile or residue from the filter dissolution. As before, the fiber loading on Samples 5 and 6 was not signifi.cantly higher than the loading on Samples 7 and 8.
Conclusions: From the results of the microscopic analyses, the following conclusions can be drawn.
1. The lining material in both the dryers is primarily chrysotile.
2. The po1ycarbonate and polystyrene filters, both samples and blanks, contain small amo~nts of chrysotile.
3. TEM and SEM analyses indicate that the polycarbonate
and polystyrene filters from CPSC 7166 and 7167 do not' -
contain a significantly higher loading of chrysotile than the blanks (polystyrene filter 7 and 8).
4. Based on the qualitative analysis, there was no apparent difference in the fiber,size distribution
'ft.. betw~eesanmple and blank.
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J- ~ '-L< I; . 74- .
Gt'ohn A. Small, Research Chemist
/ ,:t(,/],,,WI.r/ . /" ' "
Harry ~ Rook
Acting Chief
.
c:..--
Gas & Particulate Science
Division ..
Eric B. Steel Research Chemist
Directo Center for Analytical Chemistry
Robert W. Burke Service Ana~ysis Coordinator Center for Analytical Shemistry
79-92
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GI00083
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F1Sure 7: seconcary electron 1~se CPSC , 7166
Figure 8: Enerhy ~ispersive x-ray ~n~lysis of fi~er sh~~n ln iiiurc 7
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GI00084
'Fi;ure one: n:!! lC:l;a of insulating ~aterial fro~ CPSC !J 7166
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