p.1 

OAR Box 1811 

Prepped by Keeia Richards 

Document Number: 

29) ll-A-10 

Docket Number: 

A-84-22 

Printed 10/30/2008 1:19:24 PM Sheet 29 of 82 
P.2 

August 1984 

EVALUATION OF TRAINED VISIBLE EMISSION 

OBSERVERS FOR FUGITIVE EMISSION OPACITY MEASUREMENT 

ENVIROWIENTAL SCIENCES RESEARCH LABORATORY 

OFFICE OF RESEARCH AND DEVELOPMENT 

U.S. ENVIRONMENTAL PROTECTION AGENCY 

RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711 
P.3 

EVALUATION OF TRAINED VISIBLE EMISSION 

OBSERVERS FOR FUGITIVE EMISSION OPACITY MEASUREMENT 

by 

Thomas H. Rose 

Eastern Technical Associates 

2412 Atlantic Avenue 

Raleigh, North Carolina 27658 

Contract 68-02-3480 

Project Officer 

William D. Conner 

Emissions Measurement and Characterization Division 

Environmental Sciences Research Laboratory 

Research Triangle Park, North Carolina 27711 

ENVIRONMENTAL SCIENCES RESEARCH LABORATORY 

OFFICE OF RESEARCH AND DEVELOPMENT 

U.S. ENVIRONMENTAL PROTECTION AGENCY 

RESEARCH TRIANGLE PARK, NORIH CAROLINA 27711 
P.4. 

DISCLAIMER 

This report has been reviewed by the Environmental Sciences Research 

Laboratory, U.S. Environmental Protection Agency, and approved for publication. Approval does not signify that the contents necessarily reflect 

the views and policies of the U.S. Environmental Protection Agency, nor 

does mention of trade names or commerical products constitute endorsement 

or recommendation for use. 

11 
P.5 

ABSTRACT 

The stack of a visible emission training school smoke generator was 

modified to emit white or black snake in a horizontal direction near 

ground-level to simulate fugitive emissions. Trained anoke observers 

measured the opacity of these simulated fugitive emissions against a 

dark terrestrial background and under clear sky lighting conditions. 

They measured both white and black emissions generated at four different 

opacities — 15, 20, 30 and 40%. The observers also measured the same 

opacity of smoke plumes emitted fron an unmodified training school smoke 

generator. These vertical-flow smokestack plumes were evaluated against 

a sky background to provide reference data on the observers ability to 

measure the opacity of conventional stack plumes under the same clear sky 

lighting conditions used for the fugitive plume tests. 

The observers measured opacities of white fugitive emissions with 

accuracies similar to the conventional stack emissions when opacities 

were in the range of 15 to 20%. As opacity increased, however, the 

observers increasingly underestimated opacity. At 40% opacity, observer 

measurements were lower on average by about 8% opacity. The opacities 

of black fugitive emissions were underestimated at all opacity levels. 

Opacity was lower on average by 5% opacity at the 15% opacity level and by 

11% opacity at the 40% opacity level. It was also observed that for both 

white and black simulated fugitive emission plumes, the observers sensitivity to changes in opacity levels declined relative to the conventional 

vertical stack plumes. 

This report was submitted in fulfillment of Contract No. 68-02-3480 

by Eastern Technical ssociates under the sponsorship of the U.S. Environmental Protection Agency. The report covers the period of September 30, 

1980 to September 30, 1981 and work was completed November 16, 1981. 

i n 
P.6 

CONTENTS 

Abstract iii 

Figures vi 

Tables vi 

Acknowledgements vii 

1 Introduction 1 

2 Conclusions and Recommendations 2 

3 Experimental Design 3 

Test Location 3 

Smoke Generators 3 

Observers 3 

Observer Tests ... . 4 

4 Data Acquisition and Quality Assurance 7 

Generator Calibration 7 

Generator Calibration Error 7 

Generator Zero and Span Drift 7 

Neutral-Density Filter Specifications 7 

Strip Chart Data Record 10 

Confidence Intervals-Generator Calibration and 

Operation 10 

Observers 10 

Documentation 10 

Tests-Plume Configuration 11 

Obscuring Mechanisn 11 

5 Results 12 

References 18 
Pl. 

FIGURES 

Number Page 

1 Modified smoke generator for emitting simulated fugitive 

emission plumes of known opacities 5 

2 Conventional smoke generator for emitting verticle 

stack plunes of known opacities 6 

3 Observer opacity evaluations versus transmissometer 

measured opacities of conventional vertical white smoke 

plumes viewed against a sky background on a clear day 13 

4 Observer opacity evaluations versus transmissometer 

measured opacities of conventional vertical black smoke 

plumes viewed against a sky background on a clear day 14 

5 Observer opacity evaluations versus transmissometer 

measured opacities of simulated white fugitive plumes 

viewed against a terrestrial background on a clear day 16 

6 Observer opacity evaluations versus transmissometer 

measured opacities of simulated black fugitive plumes 

viewed against a terrestrial background on a clear day 17 

TABLES 

1 Conventional anoke Transmissometer Calibration Data 8 

2 Simulated Fugitive smoke Transnissaneter Calibration 

Data 9 

3 Test Conditions 12 

vi 
P.8 

ACKNOWLEDGMENTS 

The cooperation and assitance of William Conner of the U.S. Environmental Protection Agency is gratefully acknowledged. We are particularly 

indebted to Ken Averitte, Eugene Jackson, Jerry Clayton, David Daniel, 

Donna Quidley, Ernie Fuller, Bryant Foust, and Gary Saunders who participated as smoke readers in the field portion of the study. 

The modification of the smoke generator was designed by Mr. Willie Lee 

of Environmental Industries. Analysis of the data was performed by 

Ms. Judy Maples, Mr. David Savage and Mr. David Brande of Eastern Technical 

Associates. 

vi 1 
P.9 

SECTION 1 

INTRODUCTION 

Many types of airborne particles and aerosols are not emitted from 

conventional vertical stacks. Instead, these emissions may came fran 

windows, roof monitors, vents, conveyor belts, hoppers, storage piles, 

construction sites, roads, and a variety of other sources. Often these 

unconfined emissions originate close to the ground and move with the wind 

in a horizontal direction; however, unlike conventional smokestack plumes 

that are viewed against the sky, these emissions are usually viewed 

against a darker terrestrial background. Researchers such as Conner 

(1,2), Himil (3), and Hood (4) have long recognized that the contrast 

betwan the plume and the backgrouind have an effect on the opacity assigned 

by observers to the emissions. The introduction to EPA Revised Method 9 

states: "Studies of the theory of opacity and field studies have demonstrated that a plume is most visible and presents the greatest apparent 

opacity when viewed against a contrasting background (5)." Atmospheric 

visibility studies have reached the same conclusions and even in nature 

it is well known that the background matching ability of chameleons 

reduce their visibility. 

This study was designed to determine the biases, if any, introduced 

when a certified Method 9 snoke reader assigns opacity values to groundlevel emissions viewed against non-sky backgrounds. 

A conventional smoke generator, used in the training and certification of trained visible emission (VE) observers, was modified to emit 

snoke plumes horizontally below the eye level of the observers, who then 

viewed the smoke plumes against a terrestrial background. Tb determine 

that the observers selected for the panel were capable of making unbiased 

opacity readings of vertical-flow stack plumes under good viewing conditions, an unmodified generator was used to produce vetical plunes for 

evaluation at the same time. 
P.10 

SECTION 2 

CONCLUSIONS AND RECOMMENDATIONS 

The study indicated that the panel of snoke readers evaluated the 

opacities of simulated white (horizontal-flow) fugitive emissions with 

accuracies similar to the (vertical-flow) stack plume opacity measurements 

when opacity levels were around 15 - 20%. As opacity levels increased, 

however, the panel increasingly underestimated them; opacity was lower on 

average by about 8% opacity at the 40% opacity level. 

Black (horizontal-flow) fugitive emissions were underestimated at 

all opacity levels. At 15% opacity, the observers measured the emissions 

5% opacity low; at 40% opacity, they measured them 11% opacity low. 

Overall, the observer panel's sensitivity to opacity changes was less for 

simulated (horizontal-flow) fugitive emissions than for conventional 

(vertical-flow) stack plumes. The change in panel opacity measurement 

per change in transnissaneter opacity measurement declined frcm near 1.00 

for stack plumes to 0.62 and 0.77 for white and black fugitive plumes, 

respectively. 

It is recommended that controlled tests of observer and transmisscmeter opacity measurements of simulated black and white fugitive 

emissions be conducted for other environmental lighting conditions, e.g., 

on an overcast day. It is also recommended that a lower opacity level 

around 5 or 10% be included in the tests. 
P.11 

SECTION 3 

EXPERIMENTAL DESIGN 

TEST LOCATION 

The field tests were conducted at a location in Raleigh, North 

Carolina where the topography of the site was well suited for the study. 

An embankment allowed the readers to be located above the fugitive smoke 

generator where they viewed the plumes against a terrestrial (vegetation) 

background. For the conventional vertical stack plume simulation the 

other generator was used and the observers moved down the embankment 

where their view was more representative of normal stack plumes with a 

sky background. 

SMOKE GENERATORS 

Two smoke generators were utilzied during each field test. The 

generators were commercially available units that are caimonly used at 

visible emission training schools. Both generators meet the EPA specifications for Method 9 training and certification as specified in the 

Federal Register (5). 

Cine generator was modified to emit a horizontal plume near ground 

level. The modification was achieved by leaving the stack in the horizontal (stored) position and installing a 90° elbow between the lower 

vertical section of the stack and the upper horizontal section of the 

stack. The elbow was caulked and shimmed to prevent leaks. This method 

of generating a horizontal plume was selected after stratification tests 

showed that the smoke remains uniformly dispersed in both vertical and 

horizontal axes near the duct exit (where a transmissometer was located) 

and in the stack exit plumes. The stratification tests consisted of 

viewing a white plume against a black velvet background at close range, 

and viewing a black plume against a white background. The appearance of 

both plumes was uniform along both axes. Tb further simulate the fugitive nature of a horizontal fugitive plume, a panel was placed in front 

of the stack end in order to block the observers* direct view of the 

emission exit point. 

The other snoke generator was set up with the stack in the normal 

upright position to emit vertical-flow smokestack plumes in the conventional manner. 

OBSERVERS 

The observers selected for the study were six inspectors from a 

state agency and two air pollution personnel fran local contractors. 

Each participant possessed a current Method 9 certification and a past 
record of accurate smoke reading, as evidenced by his ability to certify 

promptly at a smoke school. The Method 9 certification procedure is 

described in the Federal Register (6). The participants ranged in age 

from 26 to 38 years old with an average age of 31. Three possessed 

college degrees, three had associate degrees and the other two had same 

education beyond high school. Their experience at reading visible 

emissions ranges from one to eight years, with an average of 4.1 years. 

Since the test session was relatively long, observer fatigue was of 

concern. The general concensus of the observers, however, was that no 

fatigue problem was apparent despite the fact that they were required to 

read emissions for six hours, three in the morning and three in the 

afternoon. 

OBSERVER TESTS 

Both black and white simulated (horizontal-flow) fugitive emissions 

and (vertical-flow) stack plumes were tested under clear sky conditions. 

The vertical-flow plumes were tested to confirm that the observers were 

able to assign unbiased opacity values to conventional stack plumes. 

During each test, the observers were required to observe for 12 minutes. 

Within that 12-minute period, there was a period of just over six minutes 

of steady opacity smoke. The average of 24 consecutive readings by an 

observer during this six-minute period was the observers EPA Method 9 

evaluation of the snoke opacity. The opacity levels selected for the 

study were 40%, 30%, 20%, and 15%. The observers were exposed to the 

same levels from each generator, but in random order. Observers were 

given no review of emission opacities prior to testing and were given no 

instructions except how to complete the field test form and to read on 

signal. Opacity values were recorded on computer compatible data forms 

in bound books. The observers were instructed to read by a prerecorded 

tape at 15-second intervals to assure Method 9 compatibility and standardization of the time reference. At the same time, the data logger made a 

reference mark on the transmissometer strip chart record. 

To minimize any potential bias effects that may result frcm observer 

fatigue or change in the sun angle, the vertical generator was operated 

for only a few runs, then the horizontal generator was operated. This 

cycle was repeated throughout the six-hour test. Consequently, observers 

were required to shift their observation positions between those illustrated in Figures 1 and 2. 
P.13 

^^S^^~ 

Figure 1. Modified smoke generator for emitting simulated fugitive 

emission plumes of known opacities. 
P.14 

.•.•—'.•.•.•.•••••• r : .•.-!*.*:•" ••-:••;*.••. 

; ?" '•'; *.•-.•*-'.""• :•'-•• V*. ".•-V: •?.•.•?• 

tl'.i.'jl- •-'••V'.«;*>.'-'J:.''V- ; .:'V; : . 

:••"••".••:i*i'.*:*.vv*.-Vw;.v.;*.-_-

^ . •".•. :":.-r.*.-r* .*.*•-• •*»«.V5:.- J 

V;•••-•-••;-•• •:•;..•••':-.•.•.V>*V>"--:.'-1.i •-

:.'-.\.vH'. 

"^.•..•..*.f ...*. ^ :..••*•/.>.•.•.*•.>.«p.v.*ij/—: 

Figure 2. Conventional smoke generator for emitting verticle stack 

plumes of knovm opacities. 
P.15 

SECTION 4 

DATA ACQUISITION AND QUALITY ASSURANCE 

All transmissaneter data were accumulated on a strip chart recorder 

operated at one inch per minute. The recorder unit was connected to the 

transnissaneter of each of the generators during its phase of operation. 

In addition to the continuous strip chart trace of the opacity levels, 

the observation times were also marked on the charts. 

Each VE observer was provided a bound book of data forms adequate to 

last over the test period. The forms were designed for ease in data 

reduction and to provide information on the test type, test nunber, 

position of the observer in relation to the sun, and the viewing conditions. 

GENERATOR CALIBRATION 

Both generators were span calibrated after allowing a minimum of 30 

minutes warmup by alternately producing simulated opacities of 0% and 

100%. The stable 0% and 100% opacity values of each generator were 

verified by alternately switching the power to the light source on and 

off while the snoke generator was not producing smoke. This procedure 

was performed prior to conducting the laboratory calibration error tests 

described below, and the actual field session of the fugitive emissions 

study. j 

f 

i 

GENERATOR CALIBRATION ERROR , 

The error between the actual response and the theoretical linear 

response of the snoke meter was measured by inserting a series of three 

NBS traceable neutral-density filters of nominal opacity of 20, 50, and 

75% in the smoke meter pathlength. The calibration error for the 

transmissometer in each generator was determined by the filter insertion 

procedure described in the Federal Register (5). The calibration results 

are shown in Tables 1 and 2. 

GENERATOR TRANSMISSCMETER ZERO AND SPAN DRIFT 

Zero and span checks of the transnissaneters were performed periodically to measure the amount of opacity drift from the generators. This 

procedure was conducted at the end of every two tests. 

NEUTRAL-DENSITY FLTER SPECIFICATIONS 

National Bureau of Standards (NBS) traceable neutral-density filters 

of nominal opacity of 20, 50, and 75% were used to calibrate the snoke 

generators. These filters were calibrated within +2% . 
P.16 

TABLE 1. CONVENTIONAL SMOKE TRANSMISSOMETER FILTER CALIBRATION DATA 

Reading 

Number 

Transmisscmeter 

Reading 

Filter 

Value 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

72 

22 

46 

72 

22 

46 

72 

22.5 

46 

72 

21.5 

46 

72 

21.5 

46 

23.5 

46.5 

72.5 

73 

23.5 

47 

73 

23.5 

47 

73 

23.5 

47 

73 

23.5 

47 

73 

23.5 

47 

23.5 

47 

73 
TABLE 2. SIMULATED FUGITIVE SMOKE TRANSMISSOMETER FILTER CALIBRATION DATA 

P.17 

Reading 

Number 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

Transmissometer 

Reading 

80.5 

52 

18.5 

80.5 

52 

18.5 

80.5 

52.5 

20 

1 80.5 

52 

18.5 

80.5 

52 

19 

21.5 

53 

80.5 

Filter 

Value 

80 

52 

19 

80 

52 

19 

80 

52 

19 

80 

52 

19 

80 

52 

19 

19 

52 

80 
STRIP CHART DATA RECORD 

Each test was recorded on strip chart paper by a continuous trace of 

the opacity and listing the following information: * - start point, + -

stop point, test number, test type, each reading number and point at 

which a reading was made. Calibration error checks included filter 

value - percent opacity, measured value - percent opacity, calibrated by, 

date of calibration, location, generator, and filter set nunber. 

CONFIDENCE INTERVALS - GENERATOR CALIBRATION AND OPERATION 

Statistical analysis was conducted to determine the 95% confidence 

interval. Information necessary for this evaluation were (1) filter 

calibration error (from manufacturer), (2) filter calibration error check 

(actual filter value vs measured filter value), (3) plume configuration 

tests - one test for each of the four levels was verified for each study. 

The quality assurance coordinator recorded the 48 readings per test from 

the strip chart. An auditor independently read the same 48 readings per 

test frcm the strip chart for data validation and reduction purposes. 

OBSERVERS 

Qualified observers meeting the specifications of Federal Reference 

Method 9 were utilized as visible emissions evaluators. Meeting Method 9 

specifications means that each observer's maximum average deviation on 

white and black snoke did not exceed 7.5% opacity and no single error 

exceeded 15% opacity during their certification test. The participants 

were instructed prior to each study not to discuss their readings for the 

tests. The observers were not shown any plumes for reference opacities 

on the days of the studies. Eight readers participated in the study. 

DOCUMENTATION j 

Strip Chart Data 

Calibration error, strip charts for each test, and strip chart data 

forms were kept on a bound book. Each data form includes a test type, 

test number, participant number, reader position, background conditions, 

48 fifteen-second interval readings, and strip chart data reduction 

(person and date). 

Participant Data 

Each reader received a bound book containing a participant data form 

(individual's background information), field test coding form, and field 

test data forms. Each field test data form includes the following: test 

type, test number, participant nunber, reader position, background conditions, 48 fifteen-second interval readings, and the participant's signature. 

10 
P.19 

Generator Operator Log 

A generator data form, ccranents sheet, and plume configuration curves 

for all tests were in bound book format to assist the generator operator 

in providing accurate opacity levels for the tests. The generator data 

form includes a test number, test type, flat trace opacity percent, time 

period for flat trace opacity, generator operator, generator type - ETA 

for horizontal or EPA for vertical, time of test, recorder chart speet, 

and catments. 

TEST-PLUME CONFIGURATIONS 

Emissions were generated at four different opacity levels. The 

levels were selected at randcm by die tossing. Each test was conducted 

over a 12-minute period (48 readings at 15-second intervals). The timing 

of the test and reading intervals were verified by stopwatches. During 

this time period, a six-minute period for the selected flat trace opacity 

was generated for the required 24 readings at 15-second intervals. Flat 

trace opacity percent levels for both black and white smoke were (1) 15%, 

(2) 20%, (3) 30%, and (4) 40%. 

OBSCURING MECHANISM 

An obscuring mechanisn (plywood board) was used to prevent the 

readers fran directly viewing the emission point from the horizontal 

stack of the generator. This was done to make the plume more analogous 

to a fugitive plume. 

11 
P.20 

SECTION 5 

RESULTS 

To observe the effect each smoke color and mode of emission had upon 

the observers when they evaluated fugitive emissions, observer results 

were plotted against actual transnissaneter values. All tests were 

conducted on a clear day between 9 AM and 3 EM. 

Table 3 presents a matrix of the test conditions and a list of the 

corresponding figures where the data are shown. 

TABLE 3. TEST CONDITIONS 

Plume Configuration 

9moke 

Color Background Figure 

Conventional stack plume 

Conventional stack plume 

Simulated fugitive plume 

Simulated fugitive plume 

White 

Black 

White 

Black 

Clear Sky 

Clear Sky 

Dark terrestrial 

Dark terrestrial 

3 

4 

5 

6 

The test results of VE observer measurements of (vertical-flow) stack 

plumes under blue sky conditions (Figures 3 and 4 for white and black 

plunes, respectively) shew that panel (averaged observer) opacity measurements and their regression lines were close to the 1 to 1 line of agreement with the smoke generator transmi sscmeter opacity measurements over 

the range of opacities used in the study. Slopes of 1.17 and 1.01 were 

observed. The between-observer variation of the data as evidenced by the 

confidence intervals of the means was more than expected and previously 

observed for the method (2,3). The reason for this increased variation 

was not investigated but may have been due to the procedure of alternating 

the observers betwen the smoke generators during the test. The betweenobserver variation is not the focus of this study. It is the panel 

(averaged observer) opacity readings when viewing the conventional and 

simulated fugitive plumes that are compared to determine any bias in 

Method 9 trained VE observers when evaluating fugitive plumes. 

12 
P.21 

60-

5 0-

% 0 

o B 

p $<° 

a E 

c R 

i v«-

t E 

y R 

20-

10-

20 

i MEAN • 95% 

CONFIDENCE INTERVAL 

*"—**<—-<—~ REGRESSION LINE 

30 40 

—r50 

TRANSMISSOMETE R 

% opacit y 

6'0 

Figure 3. Observer opacity evaluations versus transmissometer measured 

opacities of conventional vertical white smoke plumes viewed 

against a sky background on a clear day. 

13 
P.22 

60 

7o 

0 

P 

a 

c 

i 

t 

0 

B 

$ 4 0 

E 

R 

V 3 0 

E 

y R 

CONFIDENCE INTERVAL 

REGRESSION LINE 

TRANSMISSOMETE R 

% opacit y 

6 0 

Figure k. Observer opacity evaluations versus transmissometer measured 

opacities of conventional vertical black smoke plumes viewed 

against a sky background on a clear day. 

14 
P.23_ 

The simulated fugitive emissions test results for white plumes on a 

clear day (Figure 5) indicate no systematic difference (bias) between 

observers and transmissometer values for opacities around 15 - 20%. At 

higher opacities Figure 5 indicates an increasing negative observer bias. 

At 40% opacity, this bias resulted in observer panel readings around 8% 

opacity lower than the transmissometer values. The black simulated 

fugitive emissions test results (Figure 6) indicate lower observer panel 

values at all opacity levels. At 15% opacity they were 5% opacity low, 

and at 40% opacity they were 11% opacity lower than the transmisscmeter 

values. The data also indicate that the observer sensitivity to opacity 

changes, as evidenced by the slopes of the curves, declined for both the 

white and black fugitive emission plumes. The change in observer measured 

opacities per change in transmissometer measured opacities declined from 

near 1.0 for the conventional verticle stack plume measurements to 0.62 

and 0.77 for the white and black simulated fugitive plume measurements. 

15 
P.24 

1 

1 0 

1 

2 0 30 

«^~—.—--.- REGRESSION LINE 

1 i 

4 0 50 6 

TRANSMISSOMETE R 

% opacit y • 

Figure 5. Observer opacity evaluations versus transmissometer measured 

opacities of simulated white fugitive plumes viewed against 

a terrestrial background on a clear day. 

16 
60 

5 0 -

% 0 

o B 

p $- ° 

a E 

c R 

i V " 

t E 

y .R 

2 0 -

1 0-

TRANSMISSOMETE R 

% opacit y 

Figure 6. Observer opacity evaluations versus transmissometer measured 

opacities of simulated black fugitive plumes viewed against 

a terrestrial background on a clear day. 

17 
P.26 

REFERENCES 

1. Conner, W.D. and J.R. Hodkinson. Optical Properties and Visual 

Effects of Smoke-stack Plumes, U.S. Public Health Service Report No. 

999-AP-30. NTIS PB 174-705, Springfield, Virginia, 1967. 89 pp. 

2. Conner, W.D. A Conparison between In-Stack and Plume Opacity Measurements at Oil-Fired Fover Plants, In: Proceedings of the Fourth 

National Conference on Energy and the Environment, Dayton Sect. An. 

Inst, of Chem. Eng., Dayton, Ohio, 1976. pp. 478-83. 

3. Hamil, H.F., R.E. Thomas, and N.F. Swynnerton. Evaluation and Collaborative Study of Method for visual Determination of Opacity of 

Emissions fron Stationary Sources, NTIS PB 257 948/OBA, Springfield, 

Virginia, 1975. 70 pp. 

4. Hood, K.T., and A.L. Caron. The Relationship between Particulate 

Mass Borassion Rate and Observed Plume Appearance frcm Kraft Recovery 

Furnaces, Paper 74-AP-08, presented at PNNIS-APCA Meeting, Boise, 

Idaho, November 1974. 

5. Federal Register Vol. 39, No. 219:39872-39875, November 12, 1974. 

6. Federal Register vol. 39, No. 247:24877, December 23, 1971. 

18 
P.27 

TECHNICAL REPORT DATA 

(Please read Instructions on the reverse before completing) 

1. REPORT NO. 2. 3. RECIPIENT'S ACCESSION NO. 

4. TITLE ANO SUBTITLE 

EVALUATION OF TRAINED VISIBLE EMISSION OBSERVERS FOR 

FUGITIVE EMISSION OPACITY MEASUREMENT 

5. REPORT DATE 

6. PERFORMING ORGANIZATION CODE 

7. AUTHOR'S) 

Thomas H. Rose 

8. PERFORMING ORGANIZATION REPORT NO. 

9. PERFORMING ORGANIZATION NAME ANO AOORESS 

Eastern Technical Associates 

2412 Atlantic Avenue 

Raleigh, North Carolina 27658 

10. PROGRAM ELEMENT NO. 

CDTA1D/11 - 0409 (FY-84) 

1 1. CONTRACT/GRANT NO. 

Contract 68-02-3480 

12. SPONSORING AGENCY NAME AND ADDRESS 

Environmental Sciences Research Laboratory - RTP, NC 

Office of Research and Development 

U.S. Environmental Protection Agency 

Research Triangle Park, North Carolina 27711 

13. TYPE OF REPORT AND PERIOD COVERED 

Final 10/1/80 to 10/1/81 

14. SPONSORING AGENCY CODE 

EPA/600/09 

15. SUPPLEMENTARY NOTES 

16. ABSTRACT 

A smoke generator was modified to emit white or black smoke in a horizontal direction near ground-level to simulate fugitive emissions. Observers were 

placed at a slightly higher elevation than the smoke generator and were then 

shown smoke plumes at four different opacity values against a dark terrestrial 

background. They read the opacities of the smoke and recorded their observations. 

The observers also evaluated smoke plumes from a conventional vertical emitting 

smoke generator under the same clear sky lighting conditions to determine that 

the observers had no bias when viewing normal plumes. 

For the white smoke, the observer's opacity readings of the simulated fug- . 

tive emission plumes were not significantly different than the opacity readinas 

of the conventional plumes for opacities around 15-20%. Above 20% opacity, the 

observer readings of the white fugitive plumes become increasingly lower than 

the vertical plume readings. At 40% opacity, they were lower on average by 

about 8% opacity. For the black smoke, the observer readings of the simulated 

fugitive plumes were lower at all opacity levels. At 15% opacity, they were 

on average lower by about 5% opacity, and at 40% opacity, they were lower 

by about 11% opacity. For both white and black simulated fugitive emission 

plumes, the observers sensitivity to changes in opacity levels declined 

relative to the conventional verticle stack plumes. 

17. KEY WORDS AND DOCUMENT ANALYSIS 

DESCRIPTORS b.IDENTIFIERS/OPEN ENDED TERMS c. COSATI Field/Group 

18. DISTRIBUTION STATEMENT 

RELEASE TO PUBLIC 

19. SECURITY CLASS (This Report) 

UNCLASSIFIED 

2 1 . NO. OF PAOES 

20. SECURITY CLASS (Thispage) 

UNCLASSIFIED 

22. PRICE 

EPA Form 2220-1 (Rev. 4-77) PREVIOU S EDITIO N IS OBSOLET E