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PUBLICATIONS MHny

NBSIR 86-3481

A11102 b lb S 7 2

ation of Smoke Detector

All 10261 6572 Dlogy to Quantitative

Respirator Fit Test Methodology

George W. Mulholland

Richard Bukowski

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

Benjamin Y.H. Liu

W. Szymanski

Particle Technology Laboratory

University of Minnesota

October 1986

Issued November 1986

Funded by:

QC te Occupational Safety and

200 Health Administration

• U56

#86-3481

1986

C -2

RESEARCH

INFORMATION CENTER

NBSIR 86-3481

APPLICATION OF SMOKE DETECTOR

TECHNOLOGY TO QUANTITATIVE

RESPIRATOR FIT TEST METHODOLOGY

George W. Mulholland

Richard Bukowski

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

Benjamin Y.H. Liu

W. Szymanski

Particle Technology Laboratory

University of Minnesota

October 1986

Issued November 1986

Funded by:

The Occupational Safety and

Health Administration

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

TABLE OF CONTENTS

Page

LIST OF FIGURES iv

LIST OF TABLES .... vi

Abstract 1

1 . INTRODUCTION 1

2 . LIGHT-SCATTERING TYPE SMOKE DETECTOR 4

2.1 Principle of Operation .................................... 4

2.2 Detector Sensitivity Measurements 7 2.3 Optimization of Smoke Detector Performance 11

3. CLINICAL NEBULIZERS 15

3.1 Operating Parameters and Output Rate of Nebulizers ........ 18

3.2 Droplet Size Distribution Measurement Using Oleic Acid

and Laser Optical Particle Counter 21

3.3 Droplet Size Distribution Measurement Using NaCl Aerosol

and the Differential Mobility Particle Sizer (DMPS) 26

3.4 Characteristics of the Nebulizer and Liquid Used in the

Prototype Fit Test Apparatus 31

4. DESIGN OF PROTOTYPE FIT TEST APPARATUS 36

5. OPERATION OF PROTOTYPE FIT TEST APPARATUS 45

6. SUMMARY AND DISCUSSION 48

7. ACKNOWLEDGMENTS 49

8 . REFERENCES 50

APPENDIX. TOXICITY OF CANDIDATE LIQUIDS FOR QUANTITATIVE FIT

TEST APPARATUS 51

-iii-
LIST OF FIGURES

Page

Figure 1. Schematic of light-scattering type smoke detector ...... 5

Figure 2. Monodisperse aerosol generation system ................. 8

Figure 3. Response of smoke detector L-l to monodisperse DOP . .... 10

Figure 4. Response of smoke detector L-3 to corn oil aerosol

generated by the prototype fit test apparatus .........

.

12

Figure 5. Electro Signal Lab, Inc. variable angle smoke detector 14

Figure 6. End of tape reader 16

Figure 7 . Volumetric flow rate as a function of nebulizer

operating pressure 19

Figure 8. System used to determine the droplet size distribution

of the oleic acid aerosol by means of the laser optical

particle counter ....................................... 22

Figure 9. Size distribution of oleic acid aerosol generated by

Handipak nebulizer ................ ............. ........ 24

Figure 10. Theoretical response of the PMS optical particle

counter 23

Figure 11. Comparison of the impactor measurement and ASAS-300X

measurement for oleic acid aerosol 27

Figure 12. System used to determine aerosol size distribution

from the nebulizer by means of the DMPS system ......... 28

Figure 13. Size distribution of dry NaCl particles produced by

Handipak nebulizer 30

Figure 14. Number and volume distribution obtained with the Climet

optical particle counter 32

Figure 15. Accumulative size distribution of corn oil aerosol

produced by the Hudson nebulizer 34

Figure 16. Schematic of quantitative fit test apparatus 37

Figure 17. Photograph of smoke detector L-3 in the sampling

chamber ................................................ 39

Figure 18. Power supply circuit 40

-iv-
LIST OF FIGURES (continued)

Page

Figure 19. Circuit for monitoring the protection factor 41

Figure 20. LED display on front panel of prototype fit test

apparatus 42

Figure 21. Exterior view of fit test apparatus 43

Figure 22. Interior view of fit test apparatus 44

Figure 23. Correlation between detector output and protection

factor 47
LIST OF TABLES

Page

Table 1. Characteristics and Performance of Various Commercial

Medical Nebulizers 20

Table 2. Physical Properties of Candidate Liquids for Fit Test

Apparatus ......... ............. ............ ....... ....... 33

Table 3. List of Components for Fit Test Apparatus ................ 46

-vi-
APPLICATION OF SMOKE DETECTOR TECHNOLOGY TO

QUANTITATIVE RESPIRATOR FIT TEST METHODOLOGY

•jj* G.W. Mulholland, R. Bukowski., B.Y.H. Liu and W. Szymanski

Abstract

A quantitative respirator fit test apparatus was developed based on using

a light-scattering type smoke detector for the sensing element and a clinical

nebulizer for the aerosol source. The performance of three smoke detectors

and nine clinical nebulizers considered for use in the final system are

reported. Key design features of the apparatus include the generation of a

O corn oil aerosol concentration of 500 mg/m at a flow rate of 50 Jl/min and LED

display for protection factors of 25, 50, 125, and 450. The total cost of the

component parts for the apparatus is less than $300® This apparatus is

designed to meet the need for a low cost, easy to use instrument for quantitatively monitoring a respirator's fit to a worker's face.

Keywords: corn oil aerosol, face seal, LED, nebulizer, protection

factor, quantitative fit test, respirator, smoke detector.

1 . INTRODUCTION

The use of respiratory protection devices to protect workers from harmful

air contaminants is a standard industrial hygiene practice. The effectiveness

of such devices in the actual work place is critically dependent upon the

amount of air leakage between the subject's face and the sealing surface of

the respirator. To insure that a given respirator will fit properly on a

*Particle Technology Laboratory, University of Minnesota

- 1 -
worker's face, it is necessary to perform face piece fit tests. The fit test

can either be qualitative, which depends on the worker's subjective sensation

of the presence of some substance, such as isoamylacetate (banana oil), that

has penetrated through the face seal, or quantitative, which uses instrumental

methods to detect the penetration of an aerosol through the face seal. It is

quantitative fit tests that are the subject of this study.

In the usual quantitative fit test, a corn oil aerosol is generated with

a nebulizer. A light-scattering photometer is used to measure the relative

aerosol concentration inside and outside the face mask. The test is usually

conducted with the worker wearing the respirator in a chamber or hood. The

commercially available quantitative fit test equipment, which includes an

aerosol generator, a chamber, and photometer, typically costs approximately

$10,000. In addition to the relatively high cost, the operation of the equipment requires a skilled operator for performing such operations as zeroing the

photometer, interpreting the strip chart readings, and maintaining the system.

After all, the system is comparable in complexity to a variety of state of the

art aerosol measuring devices®

The high cost of the commercial quantitative fit test system and the

attendant operator skill needed to use such systems have limited their application to relatively large industrial firms, where the financial and human

resources needed are adequate and can be justified. For small firms, namely,

those with affected workers numbering less than 50, the cost of running such a

quantitative fit test program often becomes too expensive. The availability

of a simple and relatively low cost system would greatly enhance the appeal

for a quantitative fit test system for such industries. The increased use of

-2 -
such systems would greatly improve the effectiveness of respiratory protection

programs in general*

In a joint research study by Mulholland and Liu [1], the responses of

several commonly used smoke detectors to monodisperse aerosols were studied.

Based on this study it appears that a smoke detector might be suitable as the

basic detector element in a quantitative fit test apparatus. The fact that

smoke detectors are inexpensive as a result of mass production is another

reason for utilizing this technology. The other major component of a quantitative fit test apparatus is the aerosol generator. From our experience with

a variety of nebulizers, it appears that an inexpensive clinical nebulizer

would be adequate for producing sufficient aerosol in the appropriate size

range.

This report describes our investigation of the feasibility of developing

a low cost quantitative fit test apparatus based on smoke detector technology

and clinical nebulizer technology. The operational characteristics of light

scattering type smoke detectors are presented in section 2 together with

results on the performance of three candidate smoke detectors. The

performance characteristics of nine commercially available nebulizers

including generation rate, droplet size distribution, and maximum operation

time are reported in section 3. The overall design of a prototype

quantitative fit test apparatus based on using a smoke detector and clinical

nebulizer is described in section 4. Performance characteristics of the

prototype apparatus are also discussed. The operation of the prototype fit

test apparatus is described in section 5.

-3 -
2. LIGHT-SCATTERING TYPE SMOKE DETECTOR

There are two principal types of smoke detectors in common use, the socalled photoelectric or light-scattering detector and the ionization detector.

Mulholland and Liu [1] have shown that ionization type smoke detectors are

more sensitive to small particles with diameters less than about 0.3 ym, while

the light scattering type smoke detectors are generally more sensitive to

particles larger than 0.3 ym. For our study the light scattering detector is

the detector of choice, since the mass median diameter of the test aerosol is

expected to be about 1 ym and the light scattering type detectors have a wider

dynamic range for aerosol concentration.

2.1 Principle of Operation

As the name suggests, the scattering of light by smoke particles is the

basic physical phenomenon for the light-scattering type smoke detectors. A

schematic of such a smoke detector is shown in figure 1. Smoke detectors in

the mid-seventies utilized a variety of light sources including tungsten

filament lamps and light emitting diodes (LED's) in both the visible and the

near infra-red wavelengths. By 1985 most of the commercially available smoke

detectors utilized LED's operating in the near infra-red. Both GaAs with a

spectral peak at 940 nm and GaAlAs with a peak at 880 nm and a spectral width

of about 50 nm are used. The LED's are operated in a pulsed mode with a pulse

length on the order of 100 ys and a current on the order of 0.3 amps. The

time between pulses ranges from about a second to several seconds. The short,

intense pulse produces a good signal to noise ratio without overheating the

unit, as would a continuous, intense current to the LED.

-4 -
4> (0

-5 -

Figure

1.

Schematic

of

light-scattering

type

smoke

detector
The smoke detector housing is designed to minimize reflections so that

only scattered light reaches the detector element. The detectors are

generally silicon type with a lens preceding the detector to focus the

scattered light onto the active surface of the detector. The light scattered

by the smoke particles over a certain angular range reaches the photo-detector

causing an electrical signal to be generated. This signal is amplified and is

used to trigger an audible alarm when a certain threshold level, typically 1

volt, is reached.

In our study we have used special purpose smoke detectors which produce

an analog output proportional to the intensity of the scattered light rather

than simply an audible alarm. The detector circuitry includes a sample and

hold feature to keep the signal at its peak value until the next pulse

arrives. Other features of the smoke detector circuitry include a power

supply, a pulser for the LED, and noise filtering components. Many of the

functions are performed by integrated circuits, which are now inexpensive

since the units are mass produced at a level of many thousands.

The design constraints for a smoke detector are to some extent at cross

purposes with the optimal design of a high sensitivity detector for leak test

apparatus. In fact, if the sensitivity of the smoke detector is too high, it

may have a problem with a high incidence of false alarms. By contrast, the

ideal leak test apparatus would have a sensitivity limited only by the

Rayleigh scattering from air.

- 6-
In this study, we have analyzed the performance of three presently

available analog output smoke detectors. In addition, we have measured the

dependence of detector sensitivity on scattering angle for a particular

detector configuration. Other design modifications that could improve the

detector sensitivity are also considered.

2.2 Detector Sensitivity Measurements

Two sets of detector sensitivity measurements were made. One set was

based on the generation of a monodisperse aerosol and measuring detector

output versus mass concentration of the aerosol. The second set of measurements consisted of the analog output of the detector, as configured in the

prototype fit test apparatus, versus mass concentration of corn oil aerosol

generated by the nebulizer in the prototype apparatus.

A detailed description of the monodisperse aerosol generation system is

given by Mulholland and Liu [1]. Here we briefly describe a minor variant of

this configuration, which is illustrated in figure 2. A pneumatic nebulizer

produces a polydisperse aerosol by spraying a solution of dioctylphthalate

(DOP) in isopropanol. The alcohol rapidly evaporates from the generated

droplets leaving pure DOP droplets. The aerosol then passes through an

evaporation-condensation column, in which the droplets first evaporate in the

upper half of the tube and then condense in the lower half to form a

monodisperse aerosol. The droplet size is determined by the concentration of

-7 -
I

TO MASS MONITOR

Figure 2. Monodisperse aerosol generation system.

-8-
DOP in isopropanol (2.1 volume % produces 0.3 pm droplets; 20 volume %, 0.7 pm

droplets; 100 volume %, 1.3 pm droplets). Next the aerosol is diluted and

then finally enters the smoke detector chamber. The mass concentration of the

aerosol leaving the chamber is monitored by a quartz-crystal mass monitor.

The results for light scattering detector L-l are given in figure 3. It

is seen that the detector output minus background voltage is a linear function

O O of mass concentration from about 1 mg/nr to about 25 mg/nr independent of

droplet size. The light source is a GaAs light emitting diode with a spectral

peak at 940 nm. The nominal scattering angle is 60° as measured with respect

to the transmitted beam. The noise level of the detector was found to be

± 0.025 volts, which is approximately ± 1 a. As a measure of the relative

threshold sensitivity of the smoke detectors, we use the mass concentration

of 0.7 pm DOP aerosol that produces a detector output signal equal to twice

the noise level (2a). For L-l this corresponds to a mass concentration of

0.25 mg/rn^.

The second smoke detector tested, L-2, used the same basic components for

the source and detector as L-l but was operated in a continuous mode at 100 mA

rather than in a pulsed mode. The detector contained a feedback circuit that

increased the current to the LED if smoke were detected. This design was

intended for transient smoke detection, since continuous operation of the LED

at the high current would cause over-heating. We deactivated the feedback

circuit since we were interested in the detector response to a constant

aerosol concentration. We found the threshold sensitivity for L-2 to be

0.3 mg/rn^

.

-9 -
(s*ioa) dNnouDxovs—xndj.no HOJ.oaj.3a

cuO

a

a>

05u

aia.

en

<uu

3

bO

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pti

- 10-

MASS

CONCENTRATION

(mg/m
The third smoke detector, L-3, contained a special lens/light trap

geometry such that the light was focussed in a conical ring with the detector

on line with the source. The nominal range in scattering angle was 35-45°.

O The threshold sensitivity for L-3 was found to be 0.05 mg/m . Because of its

much higher sensitivity compared to the other two smoke detectors, L-3 was

chosen for use in the prototype fit test apparatus.

The response of smoke detector L-3 was measured as a function of the mass

concentration of corn oil aerosol generated by a Hudson nebulizer used in the

prototype fit test apparatus. The aerosol mass concentration was monitored by

a high sensitivity light scattering instrument, the GCA RAM-1, with five

orders of magnitude dynamic response. As seen in figure 4, the detector

output is linear with respect to aerosol concentration over more than two

decades. The apparent sensitivity of detector L-3 to corn oil aerosol is

O about 0.3 mg/m . The apparent mass concentration indicated by the GCA RAM-1

is approximately twice the true mass concentration so that the actual

O threshold sensitivity of L-3 to corn oil aerosol is about 0.15 mg/m , which is

a factor of three greater than the threshold sensitivity of L-3 to 0.7 ym

monodisperse DOP.

2.3 Optimization of Smoke Detector Performance

Up to this point we have considered only commercially available smoke

detectors. Now we address the question: What improvements in sensitivity

Certain commercial equipment and instruments are identified in this paper in

order to adequately specify the experimental procedure. Such identification

does not imply recommendation by the National Bureau of Standards, nor does

it imply that the equipment identified is necessarily the best available for

the purpose.

- 11 -
Saturation

oo ©

©s ©

© CO

o

CO

os o

oe o

(s*|oa) aNnoaoxova - inaino uoioaiao

- 12 -

0.1

0.3

1.0

3.0

10

30

100

300

APPARENT

MASS

CONCENTRATION

(mg/m

3)
might be possible with minor design changes in the smoke detector? One of the

smoke detectors studied by Mulholland and Liu [1], S-2, had a sensitivity of

about 0.03 mg/m^ for DOP aerosol. This is several times more sensitive than

L-3. The major difference in design between S-2 and L-3 is in the scattering

angle. The scattering angle for S-2 is about 20° while for L-3 is about

40°. Unfortunately, smoke detector S-2 is no longer manufactured.

In order to determine the optimum scattering angle for the corn oil

aerosol produced by the Hudson nebulizer, measurements were performed at

Electro Signal Lab, Inc. to determine the smoke detector output as a function

of scattering angle from 20° to 60° (Fig. 5). An angle of 60° corresponds to

the nominal angle used in the commercial smoke detector. As the scattering

angle is decreased, the detector output increased for the corn oil aerosol,

which has a mass median diameter of about 1 pm. This result is consistent

with Mie theory prediction for enhanced forward scattering for particle size

comparable to the wavelength of light. The relative enhancement to the

scattering intensity at 60° was a factor of 3 at 40°, a factor of 6.5 at 30°,

and a factor of 9.5 at 20°. As the scattering angle is made smaller and

smaller it becomes increasingly more difficult to shield the silicon detector

from the LED beam.

The sensitivity of smoke detectors could also be improved by modifying

the electronic design. Two of the most promising changes are detection

synchronous with the pulsing of the LED and the use of shorter, more intense

pulses of light. There is a commercially available aerosol instrument, GCA

RAS-1, based on the same generic technology as smoke detectors but is advertised to have a threshold sensitivity of 0.01 mg/m , which is a factor of 15

more sensitive than L-3.

- 13 -
-14

Figure

5.

Electro

Signal

Lab,

Inc.

variable

angle

smoke

detector.

The

shield

at

the

center

of

the

picture

prevents

the

light

beam

from

directly

reaching

the

detector.
As our last point in regard to smoke detectors, the optical assemblies of

smoke detectors lend themselves to miniaturization. The electronic industry

has taken advantage of this fact in the design of a miniature, end of tape

reader (Fig. 6). The advantage of such a design for fit testing would be to

position the detector inside the face mask so that an in situ measurement of

leakage could be made.

3. CLINICAL NEBULIZERS

This section presents results of a screening test of several commercial

medical nebulizers. The purpose of the test is to identify a low-cost

nebulizer that is suitable for use as a generator for producing test aerosols

of a stable, high concentration in quantitative fit tests of respirators.

A nebulizer is a device for producing aerosols of fine particles by the

pneumatic atomization of liquids. Either soluble or insoluble materials may

be aerosolized by nebulizing a solution or a suspension of the aerosol

material. The nebulizer is capable of producing high concentration of

aerosols with good stability. Important performance parameters of the

nebulizer include:

(a) liquid output rate, in ml /min,

O (b) aerosol concentration, in particles/cm ,

(c) droplet size distribution,

(d) aerosol volumetric output, in 1/min,

(e) maximum and minimum volumes of liquid required for operation, in ml,

(f) maximum operating time for stable operation.

- 15-
16

Figure

6.

End

of

tape

reader.

The

LED

and

the

Silicon

detector

are

located

in

line

with

the

two

holes

at

the

top

of

the

picture.
All these parameters are important in the selection of a suitable nebulizer

for face mask fit tests.

All the above mentioned parameters have been determined in the tests

reported here and are summarized in this report. Two methods were used to

determine the droplet size distribution. In one method, a pure, undiluted

oleic acid was nebulized and the aerosol produced was measured by a laser

optical particle counter (OPC, PMS-ASAS-300X) . In the second method, an

aqueous solution containing 0.1% by weight of NaCl was nebulized and the

aerosol produced was measured by the TSI Model 3932 Differential Mobility

Particle Sizer (DMPS). The first method was used because the pure oleic acid

aerosol gave the desired particle size for actual face mask testing. However,

because of the non-ideal behavior of the laser OPC in the measured size range,

the OPC measurement gave inaccurate results for the determination of the

geometric standard deviation. Consequently, the second method was used to

measure the particle size of the dry NaCl aerosol. The droplet size

distribution was then calculated from the measured size distribution of the

NaCl particles and the volumetric concentration of the NaCl in the nebulizing

solution. The actual measurement was made with a DMPS system which is capable

of giving high resolution and accurate particle size information in this size

range. Since all the droplets contained the same concentration of nonvolatile solute, the geometric standard deviation of the dry particles should

be the same as that of the droplets. In addition, the mean droplet size can

be calculated from the known concentration of solute in the solution.

- 17 -
3.1 Operating Parameters and Output Rate of Nebulizers

Most nebulizers required an operating pressure of the compressed air

supply of about 0.7 - 3.5 x 10^ Pa (10-50 psig). The corresponding volumetric

air flow rate was found to be between 4 and 23 L/min. Figure 7 shows this

relationship for seven of the nebulizers tested. Depending on the design of

the liquid reservoirs, the maximum amount of liquid that the nebulizers could

hold for stable operation varied between 5 and 25 ml. These three quantities

are shown in the first three columns in Table 1.

The liquid output rate, in ml/min, of the nebulizer was measured by

nebulizing a pure oleic acid liquid and monitoring the weight loss with time

of the nebulizer due to aerosolization of the liquid. Together with the known

maximum reservoir volume, the maximum operating time without refill could be

calculated for each operating condition of the nebulizers. The output rate

and the corresponding maximum operating time are shown in the fourth and fifth

columns of Table 1

.

The design and the material of construction of the nebulizers varied

greatly. Most nebulizers made use of different types of plastic materials for

the reservoirs, the nebulizing nozzles-impaction spheres, and the caps. Care

should be taken to insure that the specific plastic used in the nebulizer

construction is compatible with the aerosolizing liquid. For example, the

Cadema nebulizer was softened and partially dissolved by dioctyl sebacate.

Leaks were detected on several nebulizers between the interface of the

reservoirs and the caps. In general, these leaks were found on devices which

made use of hard plastic materials for both the caps and reservoirs. The

- 18-
VOL.

FLOW

RATE

(Ipm)

T l I r

10 20 30 40 50

PRESSURE (psrg)

Figure 7 . Volumetric flow rate as a function of nebulizer operating

pressure.

- 19-
Table

1.

Characteristics

and

Performance

of

Various

Commercial

Medical

Nebulizers

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leak-free nebulizers all had a soft and hard plastic combination at the interface. The last column, "remarks", in Table 1 contains information on the

aerosol leak and other operating difficulties encountered in some of the

nebuliziers

.

3.2 Droplet Size Distribution Measurement Using Oleic Acid

and Laser Optical Particle Counter

In the first series of tests, aerosols consisting of pure undiluted oleic

acid were generated by the nebulizers listed in Table 1 and the aerosols

produced were measured by the PMS-ASAS-300X laser optical particle counter.

Oleic acid has been considered as a candidate material for producing the test

aerosol for face mask fit testing. Oleic acid (9-octadecenoic acid, CH-^Cl^y

CH: CH(CH2 )7C02H) is a non-toxic substance with a density of 0.8935 g/ cm^ at

20 °C and refractive index of 1.4582 at X = 589 nm. Since the oleic acid was

undiluted, the measured size distribution should give the size distribution of

the nebulized droplets directly.

Figure 8 is a schematic diagram of the system used to determine the

droplet size distribution of the oleic acid aerosol by means of the laser

optical counter. The optical counter had a limited capability of counting

high particle concentration. A two stage dilution system was therefore set up

to dilute the aerosol before introducing it into the counter. The high dilution ratio, typically on the order of 10,000:1, also minimized the coagulation

of the original aerosol which had a high particle concentration of over 10^

3 particles/cm .

- 21 -
Figure 8. System used to determine the droplet size distribution of the

oleic acid aerosol by means of the laser optical particle counter.

- 22-
The measurement results are summarized in Table 1. The number median

diameter (NMD), mass median diameter (MMD) and geometric standard deviation

(a ) values were obtained by fitting a log-normal distribution to experimental

g

data using the "chi square" procedure [3]. As shown in Table 1, most of the

nebulizers gave a mass median diameter of between 1.27 and 1.4 um with a

geometrical standard deviation of 1.25 to 1.4. The number concentration

varied between about 1.6 x 10' to 4.4 x 10° particles/cm .

A typical particle size distribution shown in Figure 9 suggests the

existence of two modes which may be formed by two different aerosol generation

mechanisms. The first mode, NMD between 1.3-1. 5 um, was formed by the process

of atomization, and droplets were generated by the shattering of a liquid

stream in the fast-moving airstream. The liquid was drawn into the airflow by

the reduction in pressure in the exit region of the tube caused by Bernoulli

effect. The second mode, NMD between 0.1-0.15 um, was perhaps formed by the

agitation of air jet which created a dense foam of microscopic bubbles in the

liquid. These bubbles burst at the liquid surface and create additional fine

aerosol particles.

The geometric standard deviation from the OPC measurement was lower than

expected. This may be caused by the non-ideal characteristics of the laser

counter in the measured size range. Figure 10 shows the theoretical response

of the laser counter. It is seen that the instrument response is not a single

valued function of particle size in the size range between 0.8 and 2 um. This

non-ideal behavior causes the measured particles to be grouped into only one

or two channels of the instrument instead of the expected six to seven

channels. This would reduce the measured geometric standard deviation of the

aerosol in question.

-23 -
dQ6o-|p/ wp

"3 ® y y u Sj

BJ 3

U CO

<U CO c y

OJ i-1 bo a.

000*01

o

E

a

Q

O

0009

dQ6oip/NP

0

Figure

9

.

Number

and

mass

size

distribution

of

oleic

acid

aerosol

by

Handipak

nebulizer

at 2

x

10^

Pa

(30

psig)

operating
-I 2 3456789 2 3456789

10 I 1C

PARTICLE DIAMETER (jum)

Figure 10. Theoretical response of the PMS optical particle counter for

droplets with a refractive index of 1.45.

-25-
In addition to the above non-ideal behavior of the laser OPC, another

potential source of measurement error is that the laser OPC was calibrated

with polystyrene latex (PSL) particles, whose refractive index is different

from that of the oleic acid. However, this small difference in refractive

index is not expected to give rise to significant errors in the measurement.

Nevertheless, an impactor measurement for one nebulizer (Cadema) aerosol was

made in order to confirm the optical measurement. The result is shown in

Figure 11. Both methods are seen to give nearly the same mean particle size,

indicating the validity of the optical measurement.

3.3 Droplet Size Distribution Measurement Using NaCl Aerosol

and the Differential Mobility Particle Sizer (DMPS)

In an attempt to improve the measurement accuracy of the aerosol

geometric standard deviation, a second technique was used which involved

nebulizing an aqueous NaCl solution and measuring the resulting dry NaCl

particles. The dry NaCl particle size was about a factor of ten smaller than

the droplet size and could be measured accurately by the high-resolution,

Differential Mobility Particle Sizer (DMPS).

Figure 12 is a schematic diagram of the second measurement system. The

nebulizer was filled with 0.1% by weight of aqueous NaCl solution to about

half the maximum liquid volume and was set to the appropriate operating

pressure. Most of the output aerosol was discarded through a filter and only

a small amount of aerosol was sampled through a capillary tube flowmeter. A

dilutor was used to reduce the aerosol concentration by mixing the aerosol

with a much higher volume of particle-free air. The aerosol is diluted by a

factor of between 40 and 90 from the original concentration. The diluted

-26-
%

MASS

LESS

THAN

SIZE

PARTICLE DIAMETER (jjm)

Figure 11. Comparison of the irapactor measurement (o) and ASAS-300X

measurement (•) for oleic acid aerosol produced by a Cadema

nebulizer operated at 2 x lCr Pa (30 psig).

-27-
o

~0C

CL Hi

<o

o

&

CL

<

<

I- CL

2 > lii

llJ h N

CL >-* LU = _J

U- CQ <

U. O 2

O 2 <

1-

<

</) cn OS

2 3 LU

lii LU H*

O -J 2

2 O 3

O 3 O

O 2 O

Figure

12.

System

used

to

determine

aerosol

size

distribution

from

the

nebulizer

by

means

of

the

DMPS

system.
aerosol was allowed to pass through a drying chamber before being introduced

into the differential mobility particle sizer (DMPS). The DMPS is based on a

bipolar charging-mobility analysis technique for size distribution measurement. The size range covered by the DMPS is from about 0.01 to 0.5 um.

Figure 13 shows the measured number size distribution of the dry NaGl

particles produced by the handipak nebulizer. Both the number size distribution and the cumulative number distribution are shown. The values of NMD and

a for the dry particles are found to be 0.056 pm and 1.95, respectively.

From these parameters, the droplet size distribution parameters can be

calculated. Since every droplet had the same solution concentration, the

geometric standard deviation of the droplets distribution should be the same

as that of the dry particles distribution. The droplet NMD was calculated

from the known dry particle NMD and known solution concentration using the

following equation

3 3 DC = D p d p

where C is the NaCl concentration by weight in the aqueous solution. Dp is the

dry NaCl particle size, D^ is the droplet size, and p is the density of the

NaCl particle which was assumed to be the same as the bulk density of NaCl,

O 2.165 g/cm. Knowing the droplet NMD, the MMD of the droplet size distribution can also be calculated from the measured geometric standard deviation.

g

ln(MMD) = ln(NMD) + 3(lncr ) g

2

-29-
NUMBER CONC VS PARTICLE SIZE

AC

Hi

ffi

m

h

<

mJ

111 Ct

6

3

0

001 0.04 0.1 0.4 1.0

PARTICLE DIA. (micrometers)

CUMU NUMBER VS PARTICLE SIZE

h

Z

Ul

u

QC

Ul

CL

0.01 0.04 0.1 0.4 1.0

PARTICLE DIA. (micrometers)

Figure 13. Size distribution of dry NaCl particles produced from aerosol

generated by Handipak nebulizer at 2 x 105 Pa (30 psig)

.

“ 30-
The calculated droplet size distribution parameters are listed in Table

1. For the convenience of comparison, the parameters obtained in the first

method are also tabulated. The DMPS measurement gives a much more reasonable

geometric standard deviation than that from the laser OPC measurement. The

calculated droplet size from the NaCl aerosol is generally larger than that

from the oleic acid aerosol while the number concentration of the oleic acid

aerosol is higher than that for the NaCl aerosol. These differences are to be

expected considering the significant differences between the viscosities of

the two liquids which affect the nebulization process. There is also the

possibility of error in the case of NaCJl, since the dried residue is measured

rather than the droplet itself.

3.4 Characteristics of the Nebulizer and Liquid Used in the

Prototype Fit Test Apparatus

The Hudson nebulizer was chosen for use in the prototype quantitative fit

test apparatus. An operating pressure of 1.0 x 10^ Pa (15 psig) was used for

the nebulizer and corn oil was chosen as the aerosol source liquid for reasons

discussed below. The size distribution was obtained using a Climet optical

particle counter (model 208), which was calibrated with monosized polystyrene

spheres. The calibration curve was corrected for the difference in refractive

index from 1.59, the value for polystyrene spheres, to 1.45, the value for

corn oil, based in part on theoretical calculations by Cooke and Kerker [4].

Unlike the laser optical particle counter discussed above, the Climet, which

has a white light source, has a single valued response for the particle size

range 0.4 to 3 pm [4]. The aerosol volume distribution plotted in figure 14

has a peak near 0.5 pm and a second peak near 1.2 pm. Data obtained with the

Climet also clearly show that the Hudson nebulizer produces smaller droplets

than does the Retec nebulizer (Fig. 14).

-31 -
CO

I o

Cl, Q

CD

o

~o

~o

Par t i c [ e D 1 ame ter D,

co

rL.

a. Q

CD

O

“O

"O

Particle Diameter D

n [am]

r

Figure 14. Number and volume distribution obtained with the Climet optical

particle counter for corn oil aerosol.

- 32-
The cumulative distributions plotted in figure 15 show that the mass

median diameter obtained with the Andersen cascade impactor, 1.1 ym, is larger

than the volume mean diameter obtained with the Climet, 0.7 ym. About 80% of

the mass of the corn oil aerosol has a diameter less than 2 ym based on the

impactor data while about 95% has a diameter less than 2 ym according to the

Climet. The quantity a obtained from a straight line fit to the Climet

&

results plotted in figure 15, 1.9, agrees well with the values obtained with

the Andersen impactor, 2.0, and with the differential mobility particle sizer,

2 . 0 .

The nebulizer can be operated continuously for one hour at 1.0 x 10^ Pa

(15 psig) with corn oil before the liquid reservoir requires refilling. When

the output from the nebulizer is diluted to a total flow of 50 H/min, the

O aerosol concentration was found to be 485 mg/m . One problem with this

nebulizer as well as a number of others is the leakage between the main

housing of the nebulizer and the cap. The leakage of aerosol was greatly

reduced by placing teflon tape at the interface of the housing and cap.

A literature survey was made to determine the best liquid for use in the

nebulizer in regard to both physical properties and toxicity. We have

obtained data on the following seven candidate liquids: glyceryl

trioctanoate, glyceryl trioleate, glycerol, oleic acid, di(2-ethylhexyl)

sebacate, corn oil, mineral oil, and polyethylene glycol. The physical

properties of these liquids including density and viscosity are given in Table

2. Corn oil is currently the liquid recommended by the National Institute for

Occupational Safety and Health (NIOSH) for respirator quantitative fit testing

[5], It appears that glyceryl trioctanoate would be a better choice than corn

- 33 -
3ZIS NVH1 SS3"1 SSV1AI %

PARTICLE

DIAMETER

(pm)

Figure

15.

Accumulative

size

distribution

of

corn

oil

aerosol

produced

by

the

Hudson

nebulizer

based

on

measurements

with

the

Andersen

impactor

(o)

and

the

Climet

optical

particle

counter

().
co

03 1 HI CO1

rs, co 00 • O 1 m 1 1 vO E co • co CM 1 CM 1 03 3-i o CM CO *—=} vO co CM

-C HI Z 1 1 00 1 1 CM

CJ 03 00 CM 1 CM co 3

CO CM vO CM «—4 u~> m m P“H »—4 CM

CO3

hi

(Q

(h

COO,

a, <

jj

03

a> H

•u

•pH feMO

Oh

03 "S

•H3

O”

pHJ

0)

CO •o

•HT3C

CO CJ

4-1O

03

0)u

cuao

3-i Oh

COO

03Ss SZ

euo CM

03 i—I

J2

CO H

0)>

•H CM ^s PS

HI

X 00 CJ 00 CJm

a 00

m LO

y a) ° vO o (S. o 00 vO

CO "O HJO <r o <r o < u c • CM • CN • CM c 0 © <4H M

0) 05

—( '—r

v-' —l v-P

CJ o >> o /s p“s CJ

HI V-P /—V S'?

C CJ 0 •H CJ CJ CO CD O 0 m

CO CM CM o /^S o CO 3 H

O CM

O QJ -H -H 00 CJ 00 s-p o HI CM V.P a y p=H t—) • o co • 03 3 VP

CD • • ON • • ON pH 3 pH

©

m

•H o m ON o -h ov ON

—i

o" o CM o > CO CM MT 'w' CM 'w' -H CO 03 00 (=*«=!

>s HTO

O PS /-V P'S, •H E Mf CJ ON CJ CO CJ so- CJ

m vO

co

y

m o OV 0 (“4 0 vO o 00 co e 03 O 00 O 03 O CM O ON 03 p”4 a « • CM • • CN • CM © • • o VP O ,w o v-/ p-H V-P o o pH y

>•, •H o

HI

a '• HI

Sh

H o y

QJ rH 03y pH pQ

<JH “H HI fH pH CD 03

CO *Q sz °H JZ o CO HI S 3 b£ C >s 3 >s Sh °rt CO

f=H pH °H tiH ti

M pH pH

H pH o •H pH O 03 O 0) >s °H H co y

CO c 03

W > CD > JZ

C c > (H

p-s PS

<u CJ CJ

l-l 0 0 p-s 3 00 ov CJ

03 CM rs o

03 <—

h

O

y o —p

O

3-i o CM

Oh

p E v—

p

CO

g E 1=

sh

y o m E a o O CM

CO 9 • e > o o U

CO pH3 HI O .£ o a) s s c

•Ho

Op 0 0 o o 0 bo CJ O m 00 m O c ° H • m m

•pH r-. 1 I HI —H

pHyS y

HI bO c c H bO o o o y O 2 O vO o vO Sh OH Mr E rs. cm m rs m E H cm E \\ M M '

T3

bo E . 1 o o 0 o o y C ~s- CO m o O CM vO O O o

•H CJ CO co —» 03 00

m

m co Sh hH O •H CM CM CS3 CM —i CM CO CM X> O

CO PS r^. pH pH

Ss Ss X X

y

yy

y

HI j: s: c y i-H rH y o y Ss Ss y rH rH C pH HI rH J3 y J= HJ Ss >> y >v y O HI HI hi y JC

~a 3h HI shy IH

y

y

y rH HI iH

•H

y

y

y pH

y i y I yy o 3 y o y o y cm y CM JZ Ss y

cr So -H 5s

H Ss

w

w HI rH SS

•H iH )H pH 3h tH •h

y

H SZ

O rH

bO hj bO hi bO -a 03 ~a a. a, bo

mineral

oil >

370°C

nil

0.86

8012-95-
oil for several reasons. First it is a pure compound with well defined

properties unlike corn oil, which is a mixture of fatty acids (predominately

linoleic acid), sterols, tocopherols, antifoaming agents, and antioxidants

such as butylated hydroxyanisol (BHA). Secondly, it does not become rancid

upon long exposure to air as does corn oil. Thirdly, while there is no

definitive result at this time, it would appear that the toxic effects of

glyceryl trioctanoate would be less than those of corn oil. A short

discussion regarding our findings on the toxicity of the seven candidate

liquids is provided in the appendix. Some of the undesirable characteristics

of the corn oil would be removed if a major pure component of corn oil such as

triolein were used instead of the corn oil. In any event, we have chosen to

use corn oil in our study since it is the currently recommended liquid for

respirator fit testing.

4. DESIGN OF PROTOTYPE FIT TEST APPARATUS

To test the concept of a fit test apparatus based on a smoke detector and

a clinical nebulizer, we have assembled a prototype. The overall design of

the apparatus is illustrated in figure 16. The diaphragm pump, which serves

as a compressor and as a vacuum source, provides 1.0 x 10^ Pa (15 psig) to the

nebulizer. The bypass valves on the outlet and inlet to the pump are adjusted

so that the outlet pressure is 1.0 x 10 5 Pa (15 psig) and so the sample flow

rate from the face mask is 2 2,/min. The constancy of the pressure assures a

constant output from the nebulizer.

The corn oil aerosol produced by the nebulizer is diluted with air from a

blower to a concentration of about 500 mg/m^ at a flow rate of 50 Jl/min. This

-36-

flow is directed into the hood type exposure chamber where the excess flow

leaks out around the subject's shoulders.

The amount of leakage around the face seal is determined by drawing

2 2,/min of air from within the face mask into the cylindrical chamber

(0.45 i) containing the smoke detector (Fig. 17). The response time of the

smoke detector positioned in the chamber is about 15 seconds.

The smoke detector operates off a 20 V DC power supply. The electrical

diagram for the power supply is given in figure 18. A ten light LED display

is used to monitor the face seal leakage. Each LED corresponds to a protection factor and the successive LED's are on a logarithmic scale. The protection factor is the ratio of the concentration of test aerosol in the hood to

the concentration in the face mask. The higher the protection factor the

better the fit. The signal from the smoke detector is off-set from the background signal and is inverted to a positive voltage by the electrical circuit

shown in figure 19. This circuit also filters the smoke detector signal with

a time constant of about 5 seconds to prevent rapid transients from affecting

the LED display. The overall gain of the circuit is adjusted so that a 10 V

output lights the first LED, which corresponds to a protection factor of 25.

Provisions are made for adjusting both the gain and the off-set as indicated

in figure 19. The protection factors (25, 50, 125, 450) corresponding to four

of the LED's are indicated on the front panel (Fig. 20).

For ease in maintenance, the smoke detector/ chamber , the blower, and the

LED display with associated electronics are attached to the front panel of the

chassis. Figures 21 and 22 present exterior and interior views, respectively,

-38 -
figure

17.

Photograph

of

smoke

detector

L-3

in

the

sampling

chamber.
> >

>

o

o

CM

LO

CM

nrrv^

o

<

>

LO

Figure

18.

Power

supply

circuit

for

fit

test

apparatus.
Figure

19.

Circuit

for

monitoring

the

protection

factor

provided

by

the

face
Figure

20.

LED

display

on

front

panel

of

prototype

fit

test

apparatus.
Figure

21.

Exterior

view

of

fit

test

apparatus.
Figure

22.

Interior

view

of

fit

test

apparatus

illustrating

the

attachment

of

the

smoke

detector

chamber,

blower,

and

LED

display

to

the

front

panel.
of the prototype fit test apparatus. As shown in figure 21, the nebulizer is

mounted on the exterior of the instrument for ease in refilling the liquid

reservoir. A listing of the components is given in Table 3. The total cost

of these components was about $300.

5. OPERATION OF PROTOTYPE FIT TEST APPARATUS

The intended operating procedure for the prototype fit test apparatus is

as follows

:

1. Fit mask per ANSI Z 80.2-1980.

2. Don the hood assembly.

3. Fill nebulizer with corn oil and insert nebulizer into tee connection.

4. Turn on blower and smoke detector with one switch and compressor with

a second switch. (The compressor will not activate unless the blower

is on so that high aerosol deposition in the tee assembly is minimized.)

5. Observe the protection factors indicated by the LED display as the

subjects undergo the exercises specified in ANSI Z 80.2-1980.

With the assembled apparatus, we have recorded the detector output as a

function of time as the corn oil aerosol is being diluted in the chamber. The

numbers on the graph on figure 23 indicate the correspondence between protec-

-45-
Table 3. List of Components for Fit Test Apparatus 3

1. Chassis - 43 x 28 x 24 cm steel with removable front

and rear panel

2. Hudson nebulizer - 6 Jl/min output at 15 psi

3 © Cerberus RM 91 analog smoke detector

4. Thomas Compressor - 107 CA 183 up to 12 2,/min at a working pressure of 20 psig

5. Dayton Blower 2C782, 115 VAC squirrel cage blower

6 © NSM 3915L LED Display - 10 LED display based on logarithmic gain

7. Hoke needle valve

8. Gelman pleated membrane filter (2 pm pore size)

9. Chamber for detector fabricated with 8.9 cm (3-1/2")

diameter PVC pipe

10. T connector fabricated from brass to fit blower

outlet and Hudson nebulizer

11. 20 volt power supply

12. Circuit for LED display

13. MSA Comfo Hood

aCertain commercial equipment and instruments are identified in this paper in

order to adequately specify the experimental procedure. Such identification

does not imply recommendation by the National Bureau of Standards, nor does

it imply that the equipment identified is necessarily the best available for

the purpose.

-46-
4.5

oo

(0

in

— ^

LU

2

K

— oo

(S1IOA) lfldino aoioaiaa

Figure

23.

Correlation

between

detector

output

and

protection

factor
tion factor and smoke detector output. As shown on the figure, a protection

factor of at least 450 and perhaps as large as 900 may be discriminated from

the background reading. Field testing will ultimately be required to define

the highest protection factor that can be measured during routine testing.

6. SUMMARY AND DISCUSSION

By utilizing an analog smoke detector and a clinical nebulizer, both of

which are mass produced, we have developed an inexpensive quantitative fit

test apparatus with component parts costing less than $300. The apparatus is

easy to use, and the design is such that a person should be able to test

himself without an operator. One simply turns on the instrument and reads the

protection factor indicated by the LED display. In contrast, the presently

available quantitative fit test apparatuses require zeroing of the photomultiplier, interpretation of strip chart recordings, and skilled maintenance.

The instrument manuals for these apparatuses are similar in complexity to

state of the art aerosol instrumentation manuals. An equipment operator is

always required for testing.

We anticipate that our newly developed fit test apparatus will be

adequate for most routine applications. For very high protection factors or

for special applications where small changes in the protection factor must be

monitored, a more sensitive quantitative fit test apparatus such as the

Dynatech Frontier apparatus should be used.

We have discussed several design changes in the smoke detector section

including use of a smaller scattering angle and the use of shorter, more

-48-
intense LED pulse that could improve the smoke detector sensitivity to corn

oil aerosol by a factor of 10 or more. This could increase the maximum

protection factor measurable by the apparatus to 5000. We also indicated that

the sensing element can be very small, as small as a penny, allowing the

possibility of in situ monitoring of aerosol in the face mask itself.

In our apparatus we have used corn oil but with several reservations

explained in section 3. Based on reviewing the literature and contacting

toxicity experts, we recommend that glyceryl trioctanoate be considered a

candidate liquid for quantitative respirator fit testing.

7 . ACKNOWLEDGMENTS

This study was funded by the Occupational Safety and Health

Administration. The authors thank S. Steele for his design of the power

supply and circuitry for the LED display, T. Maher for his assistance in

fabricating the quantitative fit test apparatus, and D. Chamberlain for his

review of the toxicity data for various candidate liquids for use in the fit

test apparatus.

-49-
8. REFERENCES

[1] Mulholland, G.W. and Liu, B.Y.H., Response of smoke detectors to

monodisperse aerosols, J. Res. Nat. Bur. Stand. (U.S.) 85(3 ) :223-238,

May-June 1980.

[2] Lee, T.G.K., An instrument to evaluate installed smoke detectors, Nat.

Bur. Stand. (U.S.) NBSIR 78-1430, February 1978, 34 p.

[3] Kapadia, A., Data reduction techniques for aerosol size distribution

measuring instruments, Ph.D. thesis, Dept, of Mech. Eng., Univ. of

Minnesota, June 1980.

[4] Cooke, D.D. and Kerker, M. , Response calculations for light-scattering

aerosol particle counters, App. Optics 14(3) 734-739, March 1975.

[5] Schad, P.J. and Yarkin, R.J., Alternatives to di-2-ethyl-hexyl phthalate

("DOP") respirator quantitative fit testing, Nat. Inst. Occup. Safety

Health DHHS (NIOSH) Pub. No. 83-109, March 1983, 31 p.

[b] Dictionary of organic compounds, 5th edition, V. 4, Chapman and Hall,

New York, p. 4358.

[7] Registry of toxic effects of chemical substances, 1980, No. RK0895000,

National Institute of Occupational Health and Safety, V. 2:206, 1982.

[8] Krauskopf, L.G., Envir. Health Perspect., 3:61-72, 1973.

[9] Patty's industrial hygiene and toxicology, 3rd edition, V2A, G.D. and

F.E. Clayton, eds., John Wiley and Sons, New York, NY, 1981, p. 2346.

[10] Timof ievskaya, L.A., Ivandva, N.I., and Balyniva, E.S., Toxicology of

esters of ortho phthallic acid and hygenic standards for them, Inst.

Ind. Hyg. Occup. Dis., Acad. Med. Sci. USSR, Moscow, USSR. Trans.

Zabol, Iss. 3, 25-28 (1980) (CA/081/000401D)

.

[11] Carcinogenisis bioassay of di(2-ethylhexyl)phthalate, DHHS Publ. No.

(NIH) 82-1773, National Toxicology Program, National Institutes of

Health, Bethesda, MD (1982).

[12] Patty's industrial hygiene and toxicology, 3rd edition, pp. 2331, 2338.

[13] Stulta, F. and Kwon, B.K., Pulmonary pathology from inhalation of a complex mineral oil mist in dogs, rats, mice, and gerbils, Am. Ind. Hyg.

Ass. J. 39:393-399, May 1978.

[14] Sax, N.I., Cancer causing chemicals, Van Nostrand Reinhold Co., New

York, NY, 390-391, 1981.

[15] Registry of toxic effects of chemical substances, 1980:350, 1982.

-50-
APPENDIX

SUITABILITY OF CANDIDATE LIQUIDS FOR QUANTITATIVE FIT TEST APPARATUS

Glyceryl Trioctanoate (trioctanoin)

The use of trioctanoin, also known as tricapryln and glyceryl

tricaprylate , was suggested by W. Kluive from the National Institute of

Environmental Health Studies because it is bland, is readily metabolized, and

does not undergo oxidation to gummy products in ambient air.

Trioctanoin, the triester of glycerol and n-octanoic (caprylic) acid is a

naturally occurring component of many seed oils, such as palm oil, that are

extensively used as food oils, in pharmaceutical products, and cosmetics. It

is also used as a carrier for drugs that are under evaluation for their

pharmacological effects.

Kenneth Dooley from the National Center for Toxicological Research (NCTR)

reported that trioctanoin is used as a carrier for injection studies. In

three successive control studies with trioctanoin, the first resulted in no

tumors (in mice or rats), the second resulted in one tumor in 24 animals, and

the third study resulted in no tumors among the test animals. Since tumors

occur occasionally in nonexposed animals, the trioctanoin was evaluated as

quite safe. Gerd Reznik, an inhalation toxicologist with a special interest

in pathology, stated that trioctanoin exposure by the usual routes (i.e., oral

and i.v.) causes no damage to the liver. It was his opinion that there would

be no adverse effects on tissue in the airways and lungs.

- 51 -
Glyceryl Trioleate (triolein)

Triolein is a major component of many vegetable and seed oils® It is a

triester of glycerol and oleic acid, which is an 18-carbon straight-chain

molecule with a double bond between the ninth and tenth carbon atoms. There

is no data suggesting that triolein would cause any adverse effects. It does

undergo a slow oxidation at the double bond at ambient temperature in the

presence of air. This oxidation produces a gummy or resinous product that can

result in clogging.

Glycerol

Glycerol is a water soluble, hygroscopic liquid that is a component of

many naturally occurring vegetable oils including the two discussed above.

Glycerol is metabolized as a food, has a pleasant taste, and is not irritating

to the skin. One possible adverse effect of the substance was reported by

Tyson Tilden of the University of Maryland Medical School. For those rare

individuals who lack the enzyme glycerol kinase, glycerol is a neurotoxin.

Our estimated maximum body load of 35 mg was of concern to Tilden. He

suggested that the local instantaneous concentration at the cellular level in

the lung could be high enough to cause problems for susceptible individuals.

He indicated that there would be no problems for normal individuals.

While glycerol may be relatively safe, its hygroscopic nature is undesirable for a test aerosol. Also, the high viscosity of glycerol may affect the

performance of an aerosol generator using this liquid.

-52 -
Oleic acid

Oleic acid is a major component of olive oil, which has been used as a

control substance for many studies involving the exposure of mice and rats by

i.Ve, i.p., subcutaneous, and oral routes. According to Elizabeth Weisburger

of the National Cancer Institute, no problems have arisen that were attributed

to olive oil. However, no inhalation studies have been made.

While oleic acid is not reported to be harmful, the methyl ester (methyl

oleate) is reported to be an experimental tumorigenic agent [6,7].

Di(2-Ethylhexyl)Phthalate , (Dioctyl Phthalate)

Krauskop [8] reported that dialkyl phthalates are relatively harmless by

ingestion. The LD50 for rats by oral exposure is reported as about 30 g/kg by

Patty [9]. Timof ievskaya _et_ al [10] conclude that dioctyl phthalate is nontoxic and nonirritant when inhaled or topically applied. In studies with mice

and rats sponsored by the National Toxicology Program, dioctyl phthalate was

found to be a confirmed carcinogen [11]. Therefore, it seems prudent to

eliminate dioctyl phthalate from the list of candidate aerosol liquids.

Di(2-Ethylhexyl) Sebacate, (Dioctyl Sebacate)

Both dioctyl phthalate and dioctyl sebacate are widely used as

plasticizers. Dioctyl sebacate has a low level of toxicity by oral, intravenous, and inhalation routes for various test animals [12]. There is no

direct indication that it may be a carcinogen. It is currently being studied

- 53 -
as part of the 1983 FY study program for the National Toxicology Program.

There is, however, indirect evidence that it may be a carcinogen. It has been

reported that 2-ethyl-l -hexanol is a mutagen for certain Salmonela bacterial

strains. It is thought that the carcinogenic behavior of di(2-ethylhexyl)

phthalate and of di(2-ethyhexyl)adysate arises from the alcohol part of the

molecule. Dioctyl sebacate has the same alcohol group, and thus one suspects

that it will also turn out to be carcinogenic.

Another undesirable feature of dioctyl sebacate was that the Cadema

nebulizers are attacked by dioctyl sebacate.

Corn Oil

No toxicity data were found for corn oil. One objection to corn oil is

its susceptibility to air oxidation. The buildup of rancid oil in the

plumbing of the fit test apparatus will necessitate cleaning. The fact that

corn oil is not a pure compound is another disadvantage, since its properties

may depend on the source or even the batch for a particular source.

Mineral Oil

Mineral oil is used as a carrier for oral ingested medicines. However,

in the form of a mist at high concentration (100 mg/m ), mineral oil causes

permanent changes in the lungs including vacuoles of entrapped oil and oilcontaining macrophages [13]. Mineral oil studies gave results that were

"suggestive" of a carcinogenic effect [14]. Philip Albro of NIEHS was

strongly opposed to use of mineral oil, saying that it is absorbed by the body

-54 -
in greater extent than heretofore believed, and that it accumulates in the

lymph nodes. As with corn oil, mineral oil has the disadvantage that is a

mixture of compounds that may vary from one source to another.

Polyethylene glycol

Polyethylene glycol is a water-soluble synthetic polymer that is widely

used in various pharmaceutical, food, and cosmetic products. Recent tests

[15] indicate that polyethylene glycol may be carcinogenic.

-55-
NBS-114A (REv. 2-80

U.S. DEPT. OF COMM. 1. PUBLICATION OR 2. Performing Organ. Report No. 3. Publication Date BIBLIOGRAPHIC DATA

REPORT NO.

NOVEMBER 1986 SHEET (See instructions) NBSIR 86-3481

4. TITLE AND SUBTITLE

Application of Smoke Detector Technology to Quantitative Respirator Fit TestMethodology

5. AUTHOR(S)

George W. Mulholland, Richard Bukowski, B. Y« H. Liu, and V. Szymanski

6. PERFORMING ORGANIZATION (If joint or other than N 8S, see instructions)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7c Con tract/Grant No. MOR-B9F20017

S= Type of Report & Period Covered

Final Report

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City . State, ZIP)

Dr. Ching Bien

Technical Support, OSHA

Department of Labor

gOO^Cgn^g^lution Ave,NW

Washington, DC 2Q21Q

10. SUPPLEMENTARY NOTES

| | Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bi bliography or literature survey, mention it here)

A quantitative respirator fit test apparatus was developed based on using a light-scattering type smoke detector for the sensing element and a clinical nebulizer

for the aerosol source. The performance of three smoke detectors and nine clinical

nebulizers considered for use in the final system are reported. Key design features

of the apparatus include the generation of a corn oil aerosol concentration of

500 mg/m-3 at a flow rate of 50 2,/min and LED display for protection factors of 25, 50,

125, and 450. The total cost of the component parts for the apparatus is less than

$300. This apparatus is designed to meet the need for a low cost, easy to use instrument for quantitatively monitoring a respirator's fit to a worker's face.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) corn oil aerosols; face masks; nebulizers; occupational safety; protection factor;

quantitative fit test; respirators j smoke detectors

13. AVAILABILITY

[X3 Unlimited

I | For Official Distribution. Do Not Release to NTIS

i I Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

X~1 Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

62

IS. Price

$11.95

USCOMM-DC 6O43-P80