On}

i
= :
¥ fie : é
| | co + ~
=
1 rs as

FIGURE 2. SwRI TRAINED ODOR PANEL


Among a number of other findings, the public opinion odor testing
resulted in a dose-response relationship illustrated in Figure 14. This
is typical of the upper portion of the usual '"'S'" type dose-response odor
curve. For a given reduction of, say, two ''D" numbers, for example,
from "D"-6 to "D''-4, the reduction in odor objectionability is from 0.9
or 90 percent to about 0. 82 or 82 percent of the participants. The overall
improvement or percent reduction is thus 0.9-0,. 82/0.9 x 100 percent or
roughly 9 percent. This is not much improvement in public opinion or
acceptance for a fairly substantial odor intensity reduction,

Another two 'D'" number reduction from, say, "D''-4 to ''D'-2,
gives a fraction of the participants who think the odor is objectionable of
0.58 or 58 percent. The overall improvement in this case is much greater
in terms of objectionability being 0.82-0.58/0.82 x 100 percent or 29
percent. Thus, the public will recognize an improvement in diesel odor
more readily if the odor intensity from the vehicle is not strong to begin
with, This is because the odor generates a subjective response that
increases less as odor strength is increased.

One use of Figure 14 is to assess the impact of the EIP kit odor
control on public objectionability. Applying the first interim inspection
results of the EIP kit to this curve (all buses and conditions averaged with
equal weight given each), a reduction of odor from a ''D'"'-5,3 to 'D"-3.5
results in an 11 percent reduction in objectionahility, The point then is

whether the expense and trouble to retrofit city buses with the improved

13


FIGURE 6. CUTAWAY OF CATALYTIC MUFFLER
(Photo Furnished by GMC)


A diesel-powered vehicle, such as a city bus, is operated on a chassis
dynamometer to simulate road operation under laboratory conditions.
Normally, to determine the performance of a control device, a series

of odor ratings are made with the vehicle or engine in standard or un-
modified condition and then, usually the next day, with the control

system operative. Each series of tests involves replicate observations

in random order of odor produced during different operating speeds and
power levels. In addition to steady state vehicle cruise and idle, transients
such as accelerations after prolonged idle, upshift-type accelerations, and
decelerations from a cruise are simulated and the resultant odor levels
determined.

Prediction of Observed Odor by Analytical Measurements

Although the trained panel method requires expensive
and complicated sampling, dilution and presentation facilities and a
trained panel of observers, the time required to perform an engine or
vehicle evaluation is rather quick, usually one working day. There has
long been a need, however, to extend the usefulness of the trained panel
method described so that more researchers could investigate the causes
and control of diesel odor.

One approach involved correlating observed odor to exhaust
emissions that are normally measured by most well-equipped diesel
emission laboratories(8), Equations were developed for the prediction

of odor from, for example, city buses powered by 2-stroke cycle GM


TABLE 2. FUEL INSPECTION DATA FOR LOCAL AND CHICAGO
AREA DIESEL FUELS

Fuel Code EM-165-F EM-166-F EM-139-F
ASTM Designation (DF-1) (DF-2) (DF -2)
Source of Fuel Local Local Chicago
Distillation:
IBP°F 330.0 396.0 360.0
10% 360.0 428.0 398.0
20% 370.0 438.0 416.0
30% 380.0 450.0 436.0
40% 390.0 470.0 460.0
50% 416.0 488.0 480.0
60% 426.0 502.0 498.0
70% 438.0 520.0 520.0
80% 448.0 542,0 550.0
90% 460.0 570.0 584.0
EP 508.0 624.0 632.0
% Recovered 99.5 99.5 99.5
% Residue 0.5 0.5 0.5
% Dist. Loss 0.0 0.0 0.0
FIA Analysis:
Aromatics, % 15.6 26.6 34,3
Olefins, % 1.4 nil 0.6
Saturates, % 83.0 73.4 65.1
Gravity, API at 60°F 44,5 36.2 35.0

Total Sulfur, % 0,00 0.07 0.48


NG
GET IT AT wy

PS Xr
oskes prea,

} ;

FIGURE 3. SwRI BUS-TRUCK CHASSIS DYNAMOMETER



FIGURE 9. SCHEMATIC OF CROWN (STANDARD) AND NEEDLE VALVE INJECTOR TIPS


FIGURE 5, EIP EQUIPPED GM CITY BUS


TABLE 3. COMPARISON OF ODOR RATINGS
{Locally Available Name Brand Diesel Fuels)

Vetuele Bua 704 Date: August 3 & 4. 1971
un oa ape
Condition Fact Aromasle  Pungent
24 mph EM-165-F (DF-1) og
900 rpm EM-166-F (DF-2) oa
1/2 toade Net Change °
U, Statiatic t
32 mph EM-165-F {DF-1) ob
1200 rpm EM-166-F (DF-2} Pad
172 load ‘Net Change 1
Us Stattatic t
40 mph EM-165-F (DF-1) og
1500 rpm EM-166-F (DF-2} wt
U2 load Net Change con
Uy Statlatic 1
Idle EM-165-F (DF-1)
EM-166-F (DF-2)
Net Change
Uy Statlotic
Idle~ EM-165-F (DF-1) 10
Acceleration EM-166-F (DF-2) 48
Net Change ~ot
G, Statletic t

Deceteration  EM-165-F (DF-1)
EM-166-F (DF-2}
Net Change
U, Statistle

‘Engine operated at a fuel rate midway between maximum and no load fuel rate,
1Ug greater than 2, no statistical difference apparent.

TABLE 4.COMPARISON OF ODOR RATINGS
(Locally Available DF-1 and Chicago Area
DF -2 Fuels)

Vehicle Bus 704 Date August 4&6, 1972
Run . ape Hoe an ope
Conditven Fust Composite Burnt Olly Aromatic Pungent
24 mph EM-165-F (OF-1) 2 10 08 0.8 os
900 rpm EM-166-F (DF-2} 44 14 Ut vo 8
172 onde Net Change aT woe 3S We toa
Uy Statistic ° ° 0 1 0.5
32 mph EM-165-F (DF-1) 09 07 06
1200 rpm EM-166-F (DF-2) 13 10
142 toad Net Change 70.4 we
Us Starnsttc os 05
40 mph EM-165-F (DF-1) 31 10 os as
1500 rpm EM-166-F {DF-2} 39 12 10 0.8
12 lead Net Change 70.8 oe yoo os
Uy Statlottc 1 t os 1
ae EM-165-F (DF-1} 32 10 09 o7 05
EM-166-F (DF-2} 44 13 i 09 10
Net Chany we Jos 2 Ye ws
Us Stotretic ° ° 2 1 °
Idle EM-165-F (DF-1} 12000 10 a8
Acceleration EM-166-F (DF-2) 3 La 1a og
Net Change vt ca
U, Statlatic 1 t t t
Deceleration  EM-165-F (DF-1} 29 Lo 09 07 o4
EM. 166-F (DF-2} 27 to 08 05 93
Net Change 70-2 0 «Ot © 02 =0.1
U, Seatlette f 1 ' 1

*Engine operated at a fuel rate midway between maximum and no foad fel rate
TUp greater than 2, no etatistical difference apparent



13.

14,

15.

16.

17.

18,

19.

Springer, Karl J. and Dietzmann, Harry E., An Investigation of

Diesel- Powered Vehicle Odor and Smoke, Part IV, Final Report,

Contract No, 22-68-23, April 1971.

Springer, Karl J., Field Demonstration of General Motors Environ-

mental Improvement Proposal (EIP) - A Retrofit Kit for GMC City

Buses, Final Report, Contract No, 22-68-23, December 1972.

Springer, Karl J., An Investigation of Diesel- Powered Vehicle Odor

and Smoke, Part Il, Final Report, No. AR-644, Contract No. 86-67-72,
February 1968.

Springer, Karl J., Emissions From a Gasoline- and Diesel-Powered

Mercedes 220 Passenger Car, Report No. AR-813, Contract No. CPA

70-44, June 1971.

Springer, Karl J. and Ashby, H. Anthony, 'The Low Emission Car
for 1975 - Enter the Diesel", Paper No. 739133, Presented at the
Intersociety Energy Conversion Engineering Conference, Philadelphia,
Pennsylvania, August 13-16, 1973.

Springer, Karl J, and Hare, Charles T., A Field Survey to Determine

Public Opinion of Diesel Engine Exhaust Odor, Final Report, Contract

No. PH 22-68-36, February 1970.

Hare, Charles T. and Springer, Karl J., Public Response to Diesel

Engine Exhaust Odors, Final Report, Contract CPA 70-44, April 1971.

1?


Many of the components had been evaluated and reported on singly
but never as a total system. There is little doubt as to the effect of the
vertical stack in dispersing and diluting the odor better than the
bumper level exhaust prior to its reaching the motorist or pedestrian.
Whether merely diluting or dispersing the odor constitutes an acceptable
control method is unknown. If odor were considered in the group of pollu-
tants such as carbon monoxide, then the odor would have to be destroyed.
However, if odor is regarded only as a local nuisance, then dilution would
be an acceptable means to reduce that nuisance. Further studies of the effect
of the specific EIP vertical stack-equipped city bus on odor are in progress
at SwRI,

Odor and other emissions inspections were made five times; at
the beginning (1000 miles) and after five months (25,000 miles), ten
months (40,000 miles), 16 months (80,000 miles), and 24 months (115,000
miles), The measurements were made in three configurations; first with
stock muffler and stock 60S unit type injectors, second with the improved
60 LSN injectors, and last with the EIP catalytic muffler plus 60 LSN
injectors. This experimental design was predicated on the improved
injectors and catalytic muffler having the major aumpact. D¥F-1 fuel was
used throughout, and its effect will be discussed later in this paper. The
effect of ignition static timing on odor for the Detroit Diesel 6V-71 engine
had already been investigated(!3),

A significant reduction in odor was found when the improved in-

jectors were used in all three buses under most all conditions except idle.


TABLE 1. OVERALL SUMMARY OF ODOR EVALUATIONS,
TWO-YEAR FLEET TEST OF GM-EIP KIT
(Bus 704)
“D" Compose | “B" Burnt “Ouy | “A” Aromat “PTM Pangent
Sc Yet me | conten ifiesvons_| Modifications fications | Modifications | Modifications
won | Hours) te juration TSN [ESN + Cat | USN ]LSN + Cat | USN [USN + Cat | LSN [LSN + Cat [ USN [LSN + Cot
zamer | 1973] 98| 91770 | stocks | 4s] 45 | 1s] r4@ [12] 12 | 10] 10 | os) o8
900 rpm 9f15,9/1470| Modiicaon| 24] 29 | o9| 10 | o7| 09 | 07] 09 | 02] o2
172 toad Necchange }-21| 16 |[-os| -o4 |-o5] -03 |-03| -01 |-06| -06
vse | oo} o }o} o fos) + is} 1s |e] o
25,193] 2063] syi671_| Swck,s | 44] 44 rif tr [of 10 | os} os
4n4,41371| Modification | 27) 27 to | oz] 06 | oz] 03
Net Change |-17] -17 o1| -o01 |-03] -04 |-06] -05
Usiune | 0 | 0 1 is |o} o Jo 1
42a7a] 3267] yao | Stocks | a8} 48 a2] 12 fof 10 | tof 10
7128, 721M1| Modficavon | 34) 29 10] 09 | 07] 06 | os] 04
Netorange {-t4] -19 o2| -03 |-03| 04 |-05| -06
Useune | o | 0 o}| o Jo] « Jo] o
79.n22| 6.125] 22472 | Stocks | 40 12 WW 10 09
223772 | Modificavon | 21 08 08 04 on
Net Change | -19 04 03 06 08
U,Stanste | 0 0 1 ° 0
117606] 8.381] uaja2 | stocks | 46 16 " 09 09
tin | Modicavon | 28 10 10 06 04
Net Change | -18 ~06 01 3 -05
U,Sunsue | 0 0 > 0 0
32moh | 1973] 98| sn7m0 | swck,s | si] 41 | 13] 13 | 12] 12 | 10} 10 | 06) 06
1200 rpm 915,9/1470] Modfiaton| 22] 24 | 08] 08 | 07) 09 | o6| o8 | o1f o8
W2lead NetCange |-19] -07 |-0s| -os |-05] -03 |-os] -02 |-05] -05
usuise | 0 | o |o | o Jo} os | o 1 o| «
25,193] 2063] ape | Stocks | 47] 47 | us} as [ut] at ] sof 10 | os] 09
4n4,4n3M) Modticoron! 33) 31 | ar} aa fro) so | or} 07 | os) oa
NerChange |-14] -16 |-va] 04 |-o1] -01 |-03] -03 |-04/ -05
U,Sanne | 2 {2 1 is f2] + +| os | 15
a2ana|3z6a| noon |sioces | «sf as |rs} as | utp at {rol 10 | ro) 10
sna,227m| Meafeon| 32] 32 | 10] 12 | 10] 09 | 038] 06 | oa] 05
Ne Change |-13] -13 |-os} 3 |-01] -02 ;-02] 08 |-06] -05
Dsante | o | * os} ¢ is} ¢ os} os Jo | o
yaq22) 6:28) pam | socks | 44 1s wW 19 03
223712 | Modvicanon} 20 09 07 04 o
Net Change | -24 06 -08 06 -08
U,Sieuse | 0 ° ° 0 °
117606] 8,351] 1172772 | Stock,s | 45 1s 12 08 10
1ipgrz | Moddficavon | 31 "1 10 08 05
NetOhange | —14 04 02 0 05
U,Statste | 0 0 0 . °
4omph | 1.073] 98) 9717770 | sucess | 43} 43 | 13] 13 | tof 10 } 10) 10 | 08] 08
1500 rpm 905,9/14/70| Modan] 31{ 29 | 10] 09 | o9f o9 | o9] a6 | 03| 04
172 load Netchange |-12| -14 |-03} -o4 |-o1] -o1 |-o1] -04 |-0s| -o4
WSsuune | o} o |of 4 2} 6 2f oo [o] us
2593] 2063] apis | Stoce,s | 40] 40 | 12f a2 | 10] 10 | 10} 10 | os) 09
4f14,4/13/71] Moddeanon] 34] 41 | 11f 13 | 10] 10 | o8] 09 | os] 08
Net Change }-06] 401 |-01f 402 | 0 | 0 |-o2] -o1 |-o4} -o1
U,Sutsne | o | * o | fe oloe *| oe fe .
42274] 3267] 773071 | stocks | 4s] 45 13] 13 | uf oat | sof ro | taf to
718, 1727M1| Modfeaon| 31] 40 | 10] 12 | 09] 10 | 07] 09 | os! os
NeCuange |-14] 05 | -03) -01 |-02] -01 |-03] -01 |-o5] -02
Ysame | o} 2 jo} *¢ is} * Jo] 2 [a 2
79,722] 6125] 2724772 | Stocks| 4s 16 nn 10 09
2723712 | Modshcation| 25 10 07 07 03
Net Change | -20 -06 -048 03 05
Uy Sanne | Oo 0 0 ° 8
117,606] 8381] 12/2772 | Stocks| 4 13 09 09
L/if2 | Modificanon| 3's 10 08 06
Net Charge | -10 03 -01 -03
U,Sanste | 0 1s . 0



FIGURE 12, SNIFFMOBILE USED IN ODOR TESTING SURVEY


about the effect of fuel composition on diesel odor; but studies to date(11)
have shown the effect of a kerosene-type ASTM DF-1 grade of fuel to
produce about the same overall intensity as an ASTM DF-2 with a notice-
ably lighter, less pungent, acrid, penetrating, and lasting odor than the
heavier DF-2 fuel. This is one major reason why most of the 25, 000 city
buses operating in the U.S. use the more expensive DF-1 fuel. There
are a number of unresolved questions regarding the influence on perceived
odor of the sulfur in the fuel both in quantity and composition,

A number of odor maskant-type additives have been tried with
all failing to have any substantial effect on the odor intensity. Some new
odors would be introduced that would attempt to hide the predominantly
burnt-smokey and pungent odors but to little avail. Occasionally, a bus
transit system will use a maskant with reported success due generally
as much to the public announcement and public relations activity as to
the additive itself. This is not to say an additive could not be found to
mask the odors, but careful research to date has revealed only slight
or technical improvement,

Oxidation catalysts have, for many years, been considered a
standard method for reduction of diesel odor. In many instances, this
is true; but the city bus application has been the most difficult. To date,
precious metal catalysts, with greater activity and efficiency, are preferred
over less expensive, mostly ineffective copper oxide coatings that have been
proposed for bus ase(1), The city bus poses difficult conditions for a cat-

alyst, possible the most difficult since odor is many times associated

6


Detroit Diesel engines, one group of vehicles thus studied. For

brevity, only the ''D" odor intensity equation is listed on Figure 3.

This curve indicates the ability of the equation to predict observed odor.
Its precision is either good or not good depending on the end use of the
data. Although recommended for research, such predictions may not be
good enough for use in complying with an odor standard. One fundamental
fact is clear, that no matter how good the instrument or analysis it can
never be better than the panel in its precision. The panel in itself is not
particularly precise relative to other laboratory instruments.

Thus the dilemma and one stumbling block to odor research is the
lack of a relatively simple but precise indicator other than the nose. The
prototype A, D, Little instrument! 9) promises to do as well or better
than the prediction equations; but at this writing, there is insufficient data

on which to evaluate the instrument's performance with diesels in general.

ODOR CONTROL
Over the years, a number of strategies have been investigated
for the controi of diesel exhaust odor. Fuels, fuel additive treatment,
engine make and type, type of aspiration, oxidation catalysts, dilution,
fuel injector design, and engine power derating are some of the techniques

tried! 10-14),

Most odor control methods are directed to the city bus;
and, therefore, this has usually been the primary test vehicle.

To summarize the past seven years of control technology evaluation,

only a few ideas have shown merit; most have not. Not enough is known


FIGURE 1. U.S, PHS (EPA) DIESEL ODOR QUALITY -INTENSITY STANDARDS


more have an influence singly and their combination and optimization
have too long overlooked or neglected exhaust odor as an important

design factor.

Example of Diesel Odor Control

As a specific example, SwRI and the San Antonio Transit System
recently completed, on behalf of EPA, a two-year demonstration of several
city buses equipped with General Motors Truck and Coach Division's En-
vironmental Improvement Proposal (EIP), a kit of parts costing about
$1200 and an equal sum to instali(!4), Figure 5 is a rear view of one of
the buses equipped with the kit. The demonstration has national importance
since the kit was destined for some 25,000 in-service buses as a retrofit,

Claims for the kit included reduced odor, smoke, hydrocarbons,
oxides of nitrogen, carbon monoxide, interior noise, and vibration. The
components of the kit that were intended to reduce odor may be categorized
as vehicular (catalytic muffler, vertical stack) engine (1mproved injectors,
retarded injection timing) and operational (higher up and down shift auto-
matic transmission shift speed and DF-} fuel). Figure 6 is a cutaway of
the catalytic muffler while some of the used catalyst is shown in Figure 7.
Figure 8 is a cutaway of an LSN unit injector, and Figure 9 is a schematic
of a standard 60S and a needle valve tip assembly, The dark shaded area
under the valve represents the volume of fuel free to enter into the com-
bustion chamber at odd moments during the cycle. The reduction of this
residual fuel has been shown by the engine manufacturer to have substantial

impact on exhaust emssions(12),


ba Bhs 6

FIGURE 7. COPPER OXIDE ON ALUMINA TYPE OXIDATION CATALYST - USED


CONTROL OF DIESEL EXHAUST ODORS

by
Karl J. Springer, M.S., Manager
Emissions Research Laboratory
Southwest Research Institute
San Antonio, Texas

and
Ralph C. Stahman, B.S., Branch Chief
Test and Evaluation Branch
Environmental Protection Agency
Ann Arbor, Michigan

PAPER NO. 26

Presented at
Conference on Odors: Evaluation,
Utilization and Control

The New York Academy of Sciences
New York, New York

October 1-3, 1973


The local DF-1 and DF-2 fuels resulted in total odor ratings
("D" +"B" +O" + "All + "Pl") that were mostly the same. This is
shown by the first two bars of each group on Figure 11. Table 3 isa
summary of the specific ratings in which there was a statistical dif-
ference noted only in a few cases. Referring to the third bar in each
group, in Figure 11, the Chicago area super premium DF-2 fuel gave a
noticeably higher odor than that of either San Antonio fuels. A direct
comparison of the two DF-2 fuels is made on Table 4; and in practically
all instances, the difference was significant.

The panel judged the DF-1 fuel to be somewhat less harsh, pene-
trating, and lasting and thus less objectionable than the local DF-2 fuel.
The panel also rated the Chicago DF-2 fuel much more acrid, nauseating,
and objectionable than the local DF-2. Whether the increased sulfur is
the reason is unknown. It is probable that the type of sulfur in the fuel
is as important, if not more so, than the total sulfur content,

To conclude this odor control example, DF-1 fuel and improved
fuel injectors were definite recommendations from the EIP study along
with increased upshift speeds as methods to reduce city bus odor. The
Urban Mass Transit Administration, of the Department of Transportation,
announced on January 18, 1972 it would assist transit systems in retro-
fitting buses with the LSN injector and, on a lower priority, the other com-
ponents of the kit exclusive of the catalytic muffler. More data and
detailed discussion of this example of odor control from diesel buses is

contained in Reference 14,

ll


As an example, Figure 10 illustrates the odor results for one
of the three buses, The height of each bar is the sum of "D" +'"'B" +
"Oo" +"A" +'"'P" ratings and directly compares the stock, stock plus
catalytic muffler and catalytic muffler plus improved fuel injectors.
Shortly after the third inspection, the catalytic muffler was deleted from
the test program due to its general ineffectiveness.

In summing the observed intensities, about equal weight or impor-
tance is arbitrarily given to the 'D" diesel intensity and to the four qualities
combined, Table 1 lists the specific ratings for Bus 704 for each
inspection. These are reduced, average, data from the replicate runs
by the 10 trained panelists. The presence of asterisk values for the Us
nonparametric statistical test for difference indicates the net change to
be within the spread of the experimental data and not statistically dif-
ferent, There 1s no doubt the improved LSN injectors did an excellent
job, were mainly consistent, and most reductions were not only substantially
but statistically different. The catalytic muffler had little or no overall
net positive effect and occasionally a more penetrating pungent, sour odor
was found. This has, in the past, been attributed to partial conversion
of less smelly compounds into more odorous combustion intermediates.

The effect of fuel on diesel odor was studied on Bus 704, asa
part of the EIP demonstration(1 4), Inspection data for the three fuels,
two locally available name brand DF-1 and DF-2 fuels and a name brand
super premium DF-2 marketed in the Chicago area, are shown on Table 2,

The only gross difference in the two DF-2 fuels was total sulfur content.
10


1.0f-

0.9

0.8

07 -

Found Odor Objectionable

Fraction of Participants Who

05 -

0.4

oheny i It J ! !

2 3 4 5 6
Nominal “D” Rating of Odor Presented

FIGURE 14. ODOR DOSE - PUBLIC RESPONSE TO BUS-LIKE DIESEL EXHAUST ODOR


Next, a series of different odor levels will be presented. Please check the appropriate box under the figure which best expresses your feeling.

Pleasant Neutral

Unpleasant

Very
Unpleasant

Unbearable

Test 1 im im im

C]

~ O O

mw Oo Oo

Are any of these odors so bad that someone
should take steps to reduce them?

No—None of them ia

Yes—Test | im
Yes—Test 2 im

Yes—Test 3 C]

FIGURE 13.

How often do you experience odors like these?

Very often im
Fairly often im

Occasionally im
Never im

1969 SURVEY MULTIPLE ODOR TEST QUESTIONNAIRE - BACK SIDE


with exhaust temperatures from the 2-stroke diesel engine that are below
the catalyst activation temperature. Where mostly steady state, high
exhaust temperature, operation is involved, certain commercially-
available catalysts using precious metals can do an effective job of
reducing odor and eye irritants.

Engine derating, the intentional lowering of an engine's power
output by reducing fuel delivery, has little influence on perceived odor.
Diesel odor is probably best considered a product of incomplete com-
bustion much the same as carbon monoxide, hydrocarbons, and oxygenates,
such as aldehydes and acrolein, At high odor intensities, unburned HC in
the exhaust has been shown to be the simplest and best indicator of odor(8)
with acrolein,aliphatic aldehydes and formaldehyde, all odorous materials,
also helpful in the prediction equations. Other indicators of combustion
efficiency, such as CO2 and NO, have been helpful since exhaust odor gen-
erally is less as these increase,

From this, itis not surprising that engine and combustion chamber
variables can be important, Odor data from a variety of engines have been
reported(6-17) which show that most engines do produce noticeable odor but
that a few do not under almost every test condition, Why these latter engines
have essentially little or no noticeable odor, even at 100:1 dilution, is not
clear, It is not simply a function of design choice between pre-chamber versus
open chamber combustion, two-stroke versus four-stroke cycle, or turbo-

charging versus normal aspiration. Nor is it an obvious association with unit

or jerk type fuel injection systems or with types of injector design. Ali these and


Per Cent Cases Observed

100

90

80

270

60

w
°

-
o

w
°

20

10

"D" = 3.75721

+0. 46503 (ppm Acrolein)

e -0.00065 (ppm nitric oxide)
+0,00052 (ppmC hydrocarbons)
-0.09918 (percent carbon dioxide)
+0.00020 (ppm carbon monoxide)
-0.01377 (ppm formaldehyde)
+0.00794 (ppm aliphatic aldehydes)

i i _1 1 J

$0.5 $1.0 #1.5 $2.0 $2.5
"D" Residual Distribution

FIGURE 4, "D' VALUE PREDICTABILITY FROM EQUATION
GENERATED FROM A 25-BUS CORRELATION STUDY


oD EB! EON + AN eR
Nw aD oO

‘Stock Muffler 7] ‘Stock Muffler
6OLSN Injectors

GOS Injectors

nV
N

NOD OD vy Oo

ERS

Q} Catalync Muffier
S GOLSN Injectors

CN EN

"D4 1B" + HO" 4 HAM ER
oP aos wo

FINN

5 10
900 rpm, 24 mph, 1/2 toad

No aD 1 Oo

5 10

9200 rpm, 32 mph, 1/2 toad

"D4 BE MO" + AN 4 ORT

5 10 16
1500 rpm, 40 mph, 1/2 load

KSS

ONES

Idle

S|
A
SI

=

SSS

NSsg

2 Sw 1

LN LN

5 10 1
Idle-Acceleration

a

5 10
Deceteration

FIGURE 10. ODOR EVALUATION COMPARISON - BUS 704
TWO YEAR SUMMARY


detection, most recent work has been at suprathreshold intensities with
odor realistic of actual public encounter.

Most research on diesel exhaust odor control has utilized the En-
vironmental Protection Agency Diesel Odor Quality-Intensity Rating System'4),
better known as the Turk Kit after its originator, Dr. Amos Turk. The kit,
shown in Figure 1, consists of 28 plastic squeeze bottles, each partially
filled with a different intensity or odor, The kit includes an overall "D"
diesel odor in twelve steps in increasing concentration, Each concentration
is double the preceeding in order to parallel the non-linear human response
to odor, The "D" odor is made of four sub-odors or qualities. These com-
prise burnt smokey "B", oily 'O", aromatic 'A", and pungent "P" qualities
each in a 1 through 4 intensity series, 4 being strongest.

Special odor sampling, dilution, and presentation facilities(5, 6)
were developed about seven years ago by Southwest Research Institute
(SwRI) on behalf of the EPA using design criteria obtained 1n field studies
of atmospheric dilution of bus and truck exhaust, Horizontally-directed
exhaust, at bumper height from a city bus, was found to be diluted to a
minimum, reasonable level of 100:1 before being experienced by an
observer. This finding was confirmed by a later project by General
Motors Research(7), Vertically-directed exhaust from trucks was found
to be diluted 700 times as a reasonable minimum before being noticed by
the observer.

The trained panel shown in Figure 2 routinely evaluates simul-

taneously-presented dilute exhaust in terms of the Turk Kit of standards.


injector 1s justified for the seemingly small improvement in acceptance.
The answer has been an emphatic ''yes"; because until the odor intensity
is reduced, additional control measures will have difficulty in measurably

improving the acceptance of city bus exhaust odor.

SUMMARY

This paper has attempted to describe diesel exhaust odor control
efforts over the past seven years. Odor measurement and public acceptance
are necessary considerations to any discussion of odor control. A number
of odor control methods have been evaluated by the Environmental Protection
Agency 1n its continuing program of research on diesel exhaust emissions.
Examples such as improved fuel injectors for city buses are bright spots
among many failures that testify to the difficulty of odor control. More
can and is being done by manufacturers to design and develop engines with
low, essentially negligible exhaust odor. Before justifying a substantial
commitment, however, most manufacturers and other researchers will
require a less complicated measurement procedure as well as a specific
goal to work toward. Ultimately, it will require the coordinated efforts

of government and industry to remove the diesel engine as a source of odor

complaint.

ACKNOWLEDGEMENT
This paper is based in part on work performed by Southwest
Research Institute under Environmental Protection Agency Contract

PH 22-68-23.
14


7

10.

ll.

12.

Springer, Karl J., Field Demonstration of General Motors Environ-

mental Improvement Proposal (EIP) - A Retrofit Kit for GMC City

Buses, Final Report for Environmental Protection Agency, Contract
No. PH 22-68-23, December 1972,

Dietzmann, Harry E., Springer, Karl J., and Stahman, Ralph C.,
"Diesel Emissions as Predictors of Observed Diesel Odor", SAE
Paper No. 720757, National Combined Farm, Construction & In-
dustrial Machinery and Powerplant Meetings, Milwaukee, Wisconsin,
September 11-14, 1972, Also SAE Transactions.

"A Diesel Exhaust Odor Analysis System", A. D. Little, Inc.,
Cambridge, Massachusetts, Jamuary 26, 1973, Developed under
CRC-APRAC Project CAPE -7-68.

Springer, Karl J. and Hare, Charles T., "Four Years of Diesel Odor
and Smoke Control Technology Evaluations - A Summary", an ASME
Publication No, 69-WA/ APC-3.

Springer, Karl J., An Investigation of Diesel-Powered Vehicle Odor

and Smoke, Part Il, Final Report, Contract No. 22-68-23, October
1969.

Ford, H. S., Merrion, D. F., and Hames, R. J., "Reducing Hydro-
carbons and Odor in Diesel Exhaust by Fuel Injector Design", SAE
Paper No. 700734, Presented at Combined National Farm, Construction,
and Industrial Machinery and Powerplant Meetings, Milwaukee, Wis-

consin, September 14-17, 1970,

16


major cause of complaint about diesel odor, though it is, of course, not
the only cause of traffic odor nor is it the only source of diesel odor.

Its proximity to large numbers of people, because of the nature of op-
eration in both center city and residential areas, has made its exhaust
odor one of the chief air pollution complaints. Although the odor itself
has not been positively found a health hazard(2), it does qualify as a
nuisance emission as it is an annoyance and thereby affects public welfare.
The 1965 amendments to the Clean Air Act of 1963, Public Law 88-206,
as amended by Public Law 89-272, identified odor and smoke from diesel-
powered vehicles as of concern. It was the language in those amendments
which accelerated efforts to learn more about diesel odor and ways to

control it,

METHODS OF MEASUREMENT

Contrary to some other odor sources, the compounds which com-
prise diesel exhaust odor are so numerous and complex as to defy their
complete classification and direct measurement by chemical-instrumental
methods, The analytical methods that have been proposed for diesel odor
measurement rely on the human nose for calibration,

Most diesel odor research has used a trained panel of observers
to relate the intensity in mainly hedonic scales(3), More highly-trained
observers also evaluate the odor in terms of quality or character to

better describe the odor. Although initial studies involved threshold


FIGURE 8, CUT-AWAY OF LSN UNIT INJECTOR
PHOTO FURNISHED BY GMC


CONTROL OF DIESEL EXHAUST ODORS

Karl J. Springer, M.S.
Southwest Research Institute

San Antonio, Texas

Ralph C. Stahman, B.S.
Environmental Protection Agency

Ann Arbor, Michigan

INTRODUCTION

Diesel engine exhaust does not have to have a noticeable odor, yet many
diesel engines do under some conditions, The control of diesel odor, as with
other air pollutants, depends on three ''musts''. First, there must be a
way to measure and express the odor in simple, understandable, and
repeatable terms, Second, there must be a way to effect a reduction in
the odor that is feasible economically, Finally, the reduction in odor
must do something positive as far as the public 1s concerned. Work has
been in progress by government(!), industry, and independent laboratories

on all of these "musts".
This paper will briefly review the major work done in these areas
and then report on some recently-completed, unpublished results of odor

control for municipal buses, It is the city bus that has seemed to be the


TABLE 1. (Cont.) OVERALL SUMMARY OF ODOR EVALUATIONS,
TWO-YEAR FLEET TEST OF GM-EIP KIT

(Bus 704)
“D" Compose | “BTM Bumt “on ouy | “tat Aromane |“? Pungent
remain | Test Emirs) Tee | conigenuon|-Mosicatins | Modifeavons_| Nodifations | Modifiatons_|_Modvcrtions
figuration sy TLSN + Cat [LGN LSN + Gat ESN [USN + Gat [USN [LSN + Cat | USN JLSN + Cat
te tora] 98] onzmo |stoce.s | a7] 47 foes} us [anf on 14 | 09] 09

t
o} o9 | 08] 07
1

98,9140] Modsfcrtion| 40] 37 | 11] 12 | 10] O8
2 |-01) 02

1
1
NerChange |-07] -10 |-04) -03 |-o1] -03 |
2

U,Statisic | 0 ° 0 1 . . . . .
25,193] 2063 | 4/6771 Stock, S 39| 39 [12] 12 | 10] so | o9] o9 | 08) 08
44,4f13771 | Modifeation| 38] 31 | 11] 10 | 09] to | 09] 08 | 09) Os
Nevcrangs }-01} -08 |-o1| -02 |-v1] 0 o { or |+ot| -03
U,Sutste | is fe . . . ° . . .
42274| 3267 7730/71 | Stock, S a7] 37 [att 11 fof 10 | os] o9 | 07) oF
78,7127! | Modification | 44) 37 | 13) 11 | at] 10 fro] o8 | a9] oF
NetChange {+07{ 0 |402/ 9 Jason} 9 aor} -o8 |+o2] oo
Upsiarisue | 0 . 1 . . . . . . .
79,722) 6125 | 2para | stack, S as uw 10 iT) 06
213772} Modification | 28 iW 08 08 0s
Net Change | -07 ° 02 02 ot
U,Saristic | 0 * os ' .
117,606 | 8,351} 11/2/72 | Stork, S 40 13 rT 10 08
NAM | Meaveauon | 35 10 10 09 OT
Net change | -0.5 03 aT a1 -o1
. ° . . °
Wie-Accel| 1,073) 975] 9/1770 so | 20] 20 | ref 16 | 12 13) 43
9ns,9nafo 3a [ua] a3 | aif 10 | io 1o] 07
-22 |-06 7 |os} +26 |-02 -03| -06
Uy, Statishe ° a a ° 0 0 0 0
2saga| 2063] aneni_| stocks sal 64 [ar] oar [aap ae [rel ae | ast as

4n4.4n3n| Modifcavon | 44] 47 | 14] 17 | ro} 12 | 10} 10 | 99) 09
Net Change |-20] -17 {-07/ -04 |-07] -os |-01 1 |-06} -06
UySunsic | 0 0 0 1 ° 0 .

42,274 | 3,267 Stock, $ 63| 63 | 20] 20 j 19] 19 we fius} as

a0
TAB, IAIN | Modificaon| 46/ 42 | 14] 12 | 12/ tt

1
1
NetChange |-17/ -21 |-06| -08 |-o7] -o8 |-o1] -03 |-05] -07

Us Stansuc | 0 a 1 ° 0 0 . a °
79,722} 6125] 22am} stock, S ag Ww 3 10 ine
2723/72 | Modification} 39 a 09 09 10
Nez Change | -10 6 048 1 -O1
U,Stansne | * ° os . .
117,606 11/2/72 | Stock, 50 1B 12 09 12
111/72 | Modification | 35 10 " a7 07
Net Change | -15 08 or 02 05
Uy Starsie | 0 a ° . fy
Decel 1o73| 98] 9/17/70 | stock, 5 so] $9 aaf aa Paap az] rapa

9ns,9/14770| Modifcauon| 26] 36
NetChange |-33] -23
uysaume | 0 | 0

-os| -04 |-07] -03 |-08] -06

25,193{ 2,063] 4/16/71_| Stock, S so} so | 20] 20 | 14f 14 | ta} ta fas} 43

474,437] Modifaton| 28) 30 | 10] 11 | 10f 10 | o6| os | 02) 03

Netcuange |-31] -29 |-10] -09 |-04] -04 |-o6/ -07 |-12/ -10

UsStanse | 0 0 ° 0 0 ° 0 0 ° °

42274] 3,267} 730/71 | stock,S sa} ose | 9] 19 fous] na | oaa} oar | a3} a3

7728, 7727/71| Modifcanon| 27| 32 | 10/ 10 | o8| 09 | 07] 06 | oz} os
NetChange |-31| -26 |-09] -09 | -o6] -0s |-o4/ -os |-11/ -08

U,Sinsne | 0 ° ° 0 ° 0 o 0 ° fy
79,722| 6125| 272a772_| Stock, 43 14 a 10 10)
272372 | Modifcatwn| 27 09 o8| 08 03
Net Change | -16 -05 -03 02 -07
UsSiarmuc ] 0 0 15] . °
117,606) 8351] 11/2/72 | Stock, S 50 17 12] an at
1p | Motifeawon| 28 10 09) 06 04
NetChange | -22 -07 03 0s 07

Usui | 0 ° 0 ° °



Sum of Four-Run Average "D' + "B' + "O" + "A" + "PI

10.0

EM-165-F EM-166-F EM-139-F

No. | Diesel Fuel No. 2 Dnesel Fuel No. 2 Diesel Fuel (Chicago Area)

_ DV

aS
24 mph 32 mph 40 mph Idle Tdle-Accel Dece
900 rpm 1200 rpm 1500 rpm

FIGURE 11. ODOR FROM BUS 704 OPERATING ON THREE DIFFERENT FUELS


PUBLIC ACCEPTANCE OF DIESEL ODOR

To learn more about the third "must"', a study of public objection~-
ability to diesel odors was made. The approach was to obtain an individual's
reaction to a dilute sample of diesel odor presented to him in the same way
as the trained odor panel described earlier. A mobile odor-measuring
facility, the Sniffmobile, was prepared, capable of simultaneous present-
ation of known intensities of diluted city bus-like odor to 10 participants
under controlled conditions. An exterior view of this facility is shown in
Figure 12,

A unique rating scale was devised which relied on facial and bodily
reaction to the odor, This cartoon scale is shown in Figure 13 and was
quite successful in eliciting the opinion of people with widely different
ethnic and socio-economic backgrounds, The trained SwRI panel was used

to calibrate the odor levels in terms of the Turk Kit and thereby remain
compatible with control technology measurements. Two surveys were
made; the first in 1969 involving over 3000 quota sampled individuals in five
cities(18), The cities were San Antonio, Chicago, St. Louis, Phila-
delphia, and Los Angeles. Another survey, involving 2100 quota sampled
individuals at five sites in San Antonio, was made in 1970(19), The 1970
survey differed from the 1969 survey in that only one odor intensity was
presented to the participant, whereas the earlier survey presented a

series of increasing odor strengths of nominal "D"-2, 'D"'-4 and "D"'-6

intensities.

12


LIST OF REFERENCES
Somers, Joseph and Kittredge, George, "Review of Federally-
Sponsored Research on Diesel Exhaust Odors", Air Pollution

Control Association Journal, Volume 21, No, 12, December 1971.

Styles, H. E., Vrebos, J,, and Lawther, J., 'Public Health

Aspects of Air Pollution From Diesel Vehicles", World Health

Organization.

Springer, Karl J, and Ludwig, Allen C., Documentation of the

Guide to Good Practice for Minimum Odor and Smoke From Diesel-

Powered Vehicles, Final Report to the U.S. Public Health Service,
Contract No. CPA 22-69-71, November 1969.

Turk, Amos, "Selection and Training of Judges for Sensory Evaluation
of the Intensity and Character of Diesel Exhaust Odors", U.S. De-
partment of Health, Education, and Welfare, Public Health Service,
1967,

Springer, Karl J, and Stahman, Ralph C., "An Investigation of Diesel-

Powered Vehicle Odor and Smoke", National Petroleum Refiners As-
sociation, FL 66-46 presented at the Fuels and Lubricants Meeting,
Philadelphia, Pennsylvania, September 15-16, 1966,

Stahman, Ralph C., Kittredge, George, and Springer, Karl J., ''Smoke
and Odor Control for Diesel- Powered Trucks and Buses", SAE Paper
No, 680443, Mid-Year Meeting, Detroit, Michigan, May 20-24, 1968,

Also SAE Transactions.

15