Tapiw 4.—Carbon Dioxide, Oxygen Concentration and Leakage at 2-Minutes in the Drawstring and Septal Type Hoods.

Subject % C02 % Oo % Of Leakage**
Group Sex Number Sept. Drw. Sept. Drw. Sept. Drw.
Rest M 1 41 3.3 16.4 17.8 0.2 55.7
Cool 3 3.2 3.4 17.6 16.3 0.2 26.0
4 3.2 27 17.5 18.8 1.0 53.8
6 4.2 3.2 15.7 17.9 0.2 81.4
7 3.8 2.9 17.3 17.7 0.2 32.9
F 2 2.9 2.5 18.8 18.8 0.2 37.2
*39 1.8 2.3 19.0 18.2 2.5 22.8
28 2.3 1.8 18.2 19.3 1.2 41.6
*29 3.6 2.3 74 18.2 1.3 36.3
5 2.8 2.5 17.9 18.9 0.2 54.5
MEAN + S.E.M. 3.19 + .24 17.58 + .32 72 4.25
Exer. M 9 5.8 4.4 13.1 16.7 0.6 61.4
Cool 12 6.4 2.9 12.3 17.5 0.0 69.6
31 6.9 3.2 11.6 16.7 1.2 74.3
27 7.8 18 11.3 18.5 1.2 83.3
30 8.7 41 10.5 15.6 2.2 60.7
F 13 5.9 6.7 11.8 13.0 0.2 15,3
8 4.3 3.1 16.8 17.5 0.4 54.5
ret 3.1 4.3 17.8 13.9 0.2 27.6
10 4.9 2.6 12.1 17.7 0.4 63.6
36 6.6 3.3 13.8 16.9 1.0 42.2
MEAN + S.E.M. 6.01 + .51 13.11 + .76 744.21
Rest M 15 4.0 4.3 17.8 16.5 0.5 36.3
Heat 33 4.9 2.8 1.7 18.8 Ld 45.7
Ww 3.5 3.0 18.1 18.4 21 53.5
18 4.1 4.3 17.9 17.1 0.0 23.5
32 6.4 2.8 16.1 18.3 3.8 54.4
F 14 1.9 2.9 20,3. 17.6 0.3 52.7
16 3.7 2.7 17.3 17.9 0.3 53.1
*19 2.4 2.7 19.3 18.7 0.0 24.3
20 2.8 2.4 18.4 18.8 0.3 16.1
*40 2.4 21 18.8 18.7 42.9 41.6
MEAN + S.E.M. 3.74 + 45 17,88 + .48 293 + 42K
Exer. M 21 8.3 6.1 9.2 13.6 1,9 42.9
Heat 22 75 2.2 11.8 18.4 0.3 72.4
23 7.8 3.9 8.9 15.3 0.5 AL.7
24 7.2 6.7 11.0 11.0 1.0 35.0
25 7.5 3.3 7.4 17.9 1.3 81.0
F *35 6.0 O.1 13.1 18.4 1,2 79.4
34 6.1 2.2 12.4 18,2 0.9 83.9
*26 5.4 3.8 11.2 16.7 1.3 67.8
37 5.8 3.4 13.8 16.8 1.3 59.9
38 5.3 3.7 12.3 16.4 1.5 64.5
MEAN + S.E.M. 6.69 + 34 L111 & 64 L12b .18

*Indicates long hair.
**As % of Chamber Concentration (300-500 ppm)
¥#* Subject 40 (long hair) not included.

12


they had in putting on the hoods. Not surpris-
ingly, females indicated that they had some prob-
Jems getting the hoods over their hair more often
than did males, Y?(1)=4.96, p<.05. Females
were, however, superior to males in getting the
hood fully distended, as 20 of 35 women (579%)
completely inflated their hoods, while only 22 of
67 men (339%) did so, the difference being highly
significant, Y?(1)=7.81, p<.02.

Seat. Position

Incidental observations suggested that it
might be more difficult for subjects seated next
to windows to go through the procedures for
donning the hood (due to limitations in space)
than for subjects seated on the aisle. However,
comparison of “window” and “aisle” subjects on
the variables of time and the number of problems
encountered in donning revealed no significant
differences or trends. There was a difference,
however, in the number of subjects judged by
observers to have had difficulty removing the
safety hood from its packet, the “window” sub-
jects having proportionally more occurrences of
this particular problem, .v*(1)=4.09, p<.05.

IV. Discussion.

Briefing Effectiveness. The findings from this
study suggest that increasing the amount of in-
formation presented during briefings about the
use of the protective smoke hoods resulted in
several benefits. As the instructions became more
detailed, subjects tended to achieve more fully
distended hoods, have fewer problems with don-
ning hoods over glasses, and perhaps most sig-
nificantly, have more positive feelings about
using the hoods. This latter finding may have
relevance to briefings in general, since it may be
that more elaborate explanations of other safety
devices would also improve passenger feelings
about them,

Although some subjects expressed some reser-
yations about using the hoods, almost all stated
that they would use the hoods in an emergency.
The specific concern most often mentioned was
a fear of a shortage of air in the hoods, One
solution to this problem might be the inclusion
of additional information in the briefings about
the adequacy of the air supply. Feelings of
“claustrophobia” or “panic” seem to be rather
rare with this type of hood.

29

OL eee

In general, the briefing variations had little ef-
fect upon hood-donning times. The average don-
ning time of approximately 17 seconds was
comparable to donning times noted in previous
research using the Type D hoods*. It should be
noted that the times in the present study were
taken with the subjects remaining seated at all
times, and thus cannot be used as a measure of
the effects of hood-donning on overall evacuation
speed. Findings from the previous study? sug-
gest: that. evacuation times are probably not sig-
nificantly impaired by use of the hood, since
subjects are able to put on hoods while moving
toward exits. In view of the comparability of
overall donning times for subjects in this and
the previous studies, it must be expected that
hoods with the septal seal will not impede evac-
uation to any significant degree.

It is clear that subjects who encounter no
problems in opening and putting on the hood
are likely to be much more rapid than those who
do encounter problems. The major difficulty
with this type of hood seems to be finding and
spreading the neck seal in order to get. the hood
unfolded and distended. Although subjects gen-
erally were able to distend the hood sufficiently
for an adequate air supply, making the opening
of the neck seal more easily identifiable, perhaps
by outlining it in a contrasting color, might do
much to alleviate this problem. The develop-
ment of some type of automatic device to distend
the hood upon removal from its packet should
also be considered. It may also be that present
packaging procedures could be modified, perhaps
by using a slightly larger, less tightly packed
hood container, for improved hood-donning
efficiency.

Aside from modifications in the hood itself,
the findings from this study suggest that giving
the subjects some experience with the hood is
extremely effective in improving their efficiency
in use of the hoods. The number of problems
encountered, the degree of final inflation, and
the overall donning speed were markedly im-
proved when the subjects had a second trial with
the hoods. Perhaps most importantly, the sub-
jects with the poorest first trial performances
improved the most. on the second attempt. If
this finding is found to generalize to other safety
devices, changes in briefing procedures toward
giving passengers first-hand experience with
safety devices should be considered.


Chapter 5.

Effects of Variations in Safety Briefings Upon

Use of Protective Smoke Hoods*

Roger C. Smith, Ph.D.

I. Introduction.

While the protective smoke hood’ has been
shown to be effective in preventing the inhalation
of smoke, toxic gases, and flame, the utility of
the hood in an actual evacuation is largely de-
pendent upon the passenger's success in using it,
and his success, or lack of it, is likely to be a
function of the effectiveness of the preflight
safety briefing. It was the major purpose of
this study, therefore, to determine how present
airline safety briefings might be modified to best
promote successful passenger performance with
the safety hood. The following questions were
considered :

" (1) To what extent does increasing the amount
of information presented during safety briefings
influence the degree of hood-donning success (as
measured by both ease and speed of donning and
the extent of hood inflation), incidence of posi-
tive and negative feelings about hoods, and. will-
ingness to use hoods?

(2) How much of the information presented
during briefings is retained, as a function of the
amount presented, and the use of demonstrations?

(3) Does practice with a safety device (the
safety hood in this case) result in performance
improvement. of practical significance?

(4) Are there differences between men and
women. in hood-donning ability ?

II. Method.

Thirty-five females (IF) and sixty-eight males
(M) between the ages of 17 and 31 who had
never flown in a commercial aircraft were used
as subjects for this experiment. In addition,

* The assistance of Sharon Bowles, Robert Lewis, and
Richard Mooney in conducting this study is gratefully
acknowledged, as are the many contributions of E. B.
McFadden, J. D. Garner, Simpson, and J. Anderson,
of the Protection and Survival Laboratory, CAMI.

25

subjects were restricted to individuals who had
no connection with the FAA and had no prior
knowledge of the safety hoods.

Twenty-two observers were trained prior to
the onset of the study for observation of the
behavior of the experimental subjects. Observers
were familiarized with the experimental proce-
dures and their duties during the experiment.
These duties included timing of the subjects’
hood donning, rating of the subjects’ perform-
ance on a variety of variables listed in the ob-
server's rating sheet. (see Appendix B, Part 3),
and administration of the post-experimental
questionnaires to the subjects.

The experiment was conducted in a mock-up of
an airplane fuselage whose interior dimensions
were comparable to those of present day com-
mercial jet airliners. The mock-up was arranged
as a normal passenger compartment except that
the aircraft seats were removed from one side of
the passenger compartment, so that the observers
could sit facing the subjects for an unobstructed
view of the subjects’ behavior. A packet con-
taining a compactly folded Type S smoke hood
(overall packet dimensions approximately 6’ x 7’”
x 114’’) was securely taped on the seat-back in
front of each subject. The packet was positioned
so that the upper portion would tear off when
a subject. pulled on one of either of two red tabs
located at the wpper corners of the packet.

Subjects were met and initially instructed
prior to their entry into the mock-up. During
the initial instructions, they were told that they
would be participating in an experiment to test
the effectiveness of airline safety briefings, and
that they would be asked to use one of the safety
devices described in the briefing. Each subject
was then assigned to an observer who escorted
him into the cabin area, seated him and obtained
basic data from him. Observers noted the sub-
ject’s age, his educational level, whether or not


The data from the interior motion picture
films were noncontributory, since the smoke com-
pletely obscured visibility during the test trials.
Exterior film shots were also nonremarkable.

Information gained from the tape recordings
indicated that the noise generated by donning
the hoods persisted for no more than approxi
ly seven seconds. While this noise might
have some short-term interference effect, there
was no evidence of difficulty in communication
betiveen the cabin attendant and passengers once
the hood had been donned.

Tn sum, it appears, that while the hood cannot
serve to increase visibility in smoke other than
by preventing eye irritation, it does protect the
individual from the respiratory effects of smoke
and provides them with an air sample which is
relatively uncontaminated and adequate for evac-
uation purposes.

The results of the studies by McKenzie, et a/.
(Chapter 1), and McFadden and Gibbons (Chap-
ter 2), clearly establish the effectiveness of the
Type S hood in preventing the penetration of
noxious substances into the air sample enclosed
within the hood. The necessity for maintaining
effective septal seals was also noted; however,
this should present no particular problem since
the hoods are not now anticipated as a “try on”
device. In sum, it may be concluded that a
passenger wearing a hood will not become in-
capacitated due to smoke, flame, or toxic fume
inhalation, should these be present in an aircraft
due to an accident.

There are certain limitations to the hood;
however, these studies have shown them to be of
little consequence when considered in terms of

the function of the hood as a “get-me-out” de-
vice. The data contirm the obvious fact that the
supply of usable air which is enclosed within a
hood is not inexhaustible. What is important is
that the supply is adequate for time which is
likely to be required in the successful evacuation
of an aireraft.

The final question, and ultimately the most
important one, is that of how effective the hood
would be if used by the inexperienced passenger
during an evacuation, The results of the various
tests which have been conducted suggested that,
even with a minimal briefing (Chapter 5), most
passengers should be able to use the hood ade-
quately enough during an evacuation. One ob-
jection sometimes raised with respect to the use
of these hoods is that they may be a “panic”-
inducing agent. There is presently no evidence
to generally support this proposition. However,
the findings from the AIA reportt and our
studies indicate that “panic” in tests where sub-
jects were wearing hoods occurred when smoke
was introduced. Since the presence of smoke
seems to be the relevant variable, it must be
concluded that the hoods as such do not induce
panic. As a matter of fact, they may prevent
panic, since respiratory distress is absent when
hoods are used in a noxious environment. None-
theless, the hoods can be improved by the in-
corporation of a self-contained oxygen supply
and carbon dioxide removal agent. Research
into such devices is being undertaken; however,
until suitable supplies of these agents are avail-
able, it should not be forgotten that the protec-
tion afforded by the hood itself is significant and
worthwhile.

REFERENCES

1, Aerospace Industries ociation, 1968: Crashworthi-
ness Development Program Technical Group Report,
AIA CDP-2 & 4,

2. Federal Aviation Administration, 1968: Smoke Hood
Evaluation Program. Special Projcet Report, Project
Number 01271.

. McFadden, BE.
G. E., 1967

B., Reynolds, H. T.. and Funkhouser,
A Protective Pa iger Smoke Hood.

Federal Aviation Administration, Office of Aviation
Medicine Report No. AM 67-4.
+. Smith, R. C., 1968: Safety Hood Briefing Study.
Civil Acromedicat Institute Memorandum.
. A. Standards Institute, 1957: American Standard
Method for the Measurement of the Real-Ear At-
tenuation of Ear Protectors at Threshold. USAST
HOA,



relatively uniform linear fashion, whereas with
the drawstring hood this tendency was inter-
rupted when the carbon dioxide concentration
reached a level which induced hyperventilation.
The increase in depth of breathing, or pumping
action, of hyperventilation characteristically
brought a gross leakage and leveling off of car-
bon dioxide concentrations, and the development:

of a plateau in both carbon dioxide and oxygen
concentrations with the drawstring hood.

A moderate exercise level was chosen so that
all subjects might tolerate it for the duration of
the experiment. However, several experiments
were terminated due to subjects complaining of
leg or other muscular cramps and exhaustion.
Hleart rates of 160-178 indicated that some sub-

% C02 % 02 % LEAK % C02 % Op % LEAK
iol 23-17 J 20 TS] 10 Jig TS [to io ts [ 10 | ,o[ TS [10 Jog TS I TD
fos lg | | |g
| ee ° | S| ase |
sr 16- Oy | ao | 80 | 8r 16 a |80r | °
| | | mle | le le :
| re | soe . 6 oo | ae & | 60 |e
| | | ore ° | 8 | |
TH halt Lt Re ne
oO
| & | re oe | ©
2b 4b 20h 2p 4b 20h
* | | | | * | [o
0 ee a lt IL! |
79° F rest tMaxr2.s 79° F exercise tMAx+ 2-2
FEMALE {e LONG HAIR MALE Oo
% _CO2 % O2 Ye LEAK | % coe. % 02 % LEAK
ol tS TO |. as [ 72 | og TS | TD ol 18 Lr ao tS | TO jo 18 | TD
0
| aed | oe |
at 16+ oo | gob | oa 16 o® Jeot | 0%
| fe | |e :
| | | lo ej | °°
6r | ie 60 | 6 eS 12+ Qo | 60F °
| 42.9) 20° @o | ee | ° |
4h “ole | 0 le wl | . 4h | o ak 40F oo
3 |" | | 3 go) Fo | i‘
© | 08 |
2F a ab | 20 | ° ab \° 4p | 20- |
) | 0 | ole! 0 Le 0 olasatel
140° F rest tMAxs3.8 140° F exercise tMAx+ 19

Ficure 3. Plots of carbon dioxide and oxygen changes and pentane leakage at two minutes after donning in

Septal (TS) and Dra’
500 ppm as pentane).

ring (TD) hoods.
NOTE:

Leakage is expressed as percent of chamber concentration
Solid circles—long-haired females.

6

(300—


TasLe 10.—-DRAWSTRING HOOD—MALE—NORMAL TEMPERATURE—RESTING

SUBJECT #1 Age: 25 Surface Area: 1.93 Sq. M Temperature: 26°C Hood #000282
TIME—MINUTES
0 1 2 3 4 4,43,

03 3.1 3.3 3.3, 3.3 3.4
20.9 18.3 17.8 17.6 17.6 17.6

113, 107 107 100 91 99
14 10 10 10 9 12

SUBJECT #3 Age: 19 Surface Area: 1.94 Sq. M ‘Temperature: 26°C Hood #000270
0 1 2 3 4 5 6 6.50

2.0 3.4 3.2 3.2 3.2 3.2 2.7
18.3 16.3 16.3 16.4 16.6 16.8 16.8

80 81 80 82 80 82 76
15 16 16 17 17 16 18
SUBJECT #4 Age: 27 Surface Area: 1,89 Sq. M Temperature: 26°C Hood #000380
a) 1 2 3 4 5 6 6.28

2.2 2.7 2.7 2.7 2.7 2.8 2.9
19.7 18.8 18.5 18.3 18.3, 18.3 18.3

70 71 72 70 72 70 72
14 16 16 7 17 16 15
SUBJECT #6 Age: 27 Surface Area: 1.83 Sq. M Temperature: 25.5°C Hood #000247
0 1 2 3 4 5 6 6.47

2.2 3.2 3.5 3.6 3.7 3.7 3.7
19.3 17.9 17.2 17.0 16.8 16.9 16.9

72 71 76 75 75 74 90
12 il 12 12 12 13 12
SUBJECT #7 Age: 24 Surface Area: 1.87 Sq. M Temperature: 25,5° C Hood #000252
0 1 2 3 4 5 6 6.33

.03 2.2 2.9 2.9 2.9 2.9 3.8 3.5
20.9 19.0 17.7 17.2 16.8 16.8 16.5 16.5
- 61 60 56 58 58 58 59 60
- 1b 17 19 22 23 24 23 24

44


Tasie 8.—SEPTAL HOOD—MALE—ELEVATED TEMPERATURE—EXERCISING

SUBJECT #21 Age: 22 Surface Area: 186 Sq. M Temperature: 59°C Hood #000525

TIME—MINUTES
0 1 2 2,42

- 03 6.0 8.3 8.4
- 20.9 16.2 9.2 7.5
. 136 152 144 162

- 6 14 17 34
SUBJECT #22 Age: 21 Surface Area: 1,96 Sq. M Temperature: 60°C Hood #000523
0 1 2 2.50

4.9 7.5 8.3
17.3 11.8 8.7
116 102 112

17 18 26
SUBJECT #23 Age: 22 Surface Area: 2.05 Sq. M Temperature: 62°C Hood #000489
0 1 2 2,22
7.0 7.5
8.9 8.9
122 128
15 32
SUBJECT #24 Age: 22 Surface Area: 2.12 Sq. M Temperature: 60°C Hood #000493
0 1 2 2.13

- 03 6.2 74.2 7.2
- 20.9 17.3 11.0 8.9
- 124 144 140 120

- 16 21 30 32
SUBJECT #25 Age: 21 Surface Area: 1.87 Sq. M Temperature: 60°C. Hood #000513
0 1 2 3.00

a eon enn nee 03 4.3 7.5 9.0+
- 20.9 14.6 7.4 5.5

- 98 106 112 126

ew ee nen ee -- 16 12 16 26

42


Taste 14—DRAWSTRING HOOD—-MALE—ELEVATED TEMPERATURE—RESTING

SUBJECT #15 Age: 28 Surface Area: 1.83 Sq. M ‘Temperature: 59°C Hood #000361

TIME—MINUTES
0 1 2 3 4 5 6.17

2.9 4.3 4.4 5.8 5.8 5.8
18.1 16.5. 15.9 15.3 14.9 14.6

85 84 86 90 94 94
18 13 13, 13 15 14
SUBJECT #17 Age: 20 Surface Area: 1,91 8q. M Temperature: 57°C Hood #000270
0 1 2 3 4 5 6 6.43,

+03 3.0 3.0 3.0 3.4 3.2 3.4 3.4
20.9 19.2 18.4 18.2 18.0 18.1 18.0 18.0

94 98 96 94 96 98 96 100
16 14 13 13 12 12 14 10

SUBJECT #18 Age: 25 Surface Area: 2.12 8q. M Temperature: 56°C Hood #000327
0 1 2 3 4 5 6 6.33

03 2.9 4.3 4.3 4.3 4.3 43 4.3
20.0 18.5 17.1 16.3 16.5 16.5 16.4 16.4

70 78 76 78 82 78 80 80
— 16 4 13 13 12 13 15

SUBJECT #32 Age: 22 Surface Area: 1.77 Sq. M Temperature: 60°C Hood #000252
0 1 2 3 4 5 6.08

2.2 2.8 3.0 3.6 3.2 3.5
19.3 18.3 17.9 17.8 18.2 18.2

74 74 76 78 80 82
10 cat i li il 12
SUBJECT #33 Age: 25 Surface Area: 2,18 Sq. M Temperature: 60°C Hood #000327
0 1 2 3 4 5 6 6.30

03 2.8 2.8 3.0 3.0 2.8 2.8 3.0
20.9 19.6 18.8 18.1 18.1 18.3 18.5 18.6
96 94 90 92 90 94 94 92
10 9 6 7 iL 16 15 16

48


APPENDIX B

Part 1.

We would like to welcome you aboard Inter-
national Flight #49, nonstop jet service from
Oklahoma City to Chicago. Our flying time
will be approximately 1 hour and 45 minutes
and we will be flying at an altitude of approxi-
mately 28,000 feet.

We would now like to take a moment to point
out the safety features of this aircraft. There
are two exit doors in the forward cabin and two
in the aft cabin, all equipped with slides. In
addition, there are four window exits over the
wings. Please refer to the information card lo-
cated in the seat pocket in front of you for
further information.

Individual oxygen masks are located in the
compartment above your seat. In case of any
rapid change in cabin pressure, an oxygen mask
will drop down in front of you. Extinguish all
cigarettes, grasp the cup, and pull it to your face.
Put it over your nose and mouth, and breathe
normally.

(Safety hood instructions inserted here. See
Note A for the specific wording of each group’s
instructions.)

Please fasten your seatbelts now, and observe
the no smoking sign until the captain turns it
off. Also bring your chair backs and tray tables
to an upright position for take-off.

We hope you have a pleasant flight. If we can
do anything to make your trip more comfortable,
please don’t hesitate to call upon us.

NOTE A

Group 1. Safety hoods, located on the backs
of the seat in front of you, have been provided
for your added protection in the event of an
emergency. Should an emergency evacuation be
required, please put on these hoods, as the stew-
ardess is now demonstrating, prior to departing
the aircraft. Remove the hood when you are
safely away from the aircraft.

52

Briefings Groups 1 through 5

Group 2. Safety hoods, located on the back
of the seat in front of you, have been provided
for your added protection in the event of an
emergency. ‘They are to be used only in the
event of an emergency evacuation, or upon di-
rection of a crew member. The stewardess will
now demonstrate their use. To remove the hood
from its package, pull up on either red tab. Open
the hood to its maximum size by spreading the
neck seal with your hands. Then quickly pull
the hood down over your head. Remove the
hood after you are safely away from the aircraft.

Group 3. Safety hoods, located on the back
of the seat in front of you, have been provided
for your added protection in the event of an
emergency. They are to be used only in the
event of an emergency evacuation, or upon di-
rection of a crew member. The stewardess will
now demonstrate their use. To remove the hood
from its package, pull up on either red tab.
Open the hood to its maximum size by spreading
the neck seal with your hands and shaking it
out as the stewardess is now doing to fill it with
air. Then quickly pull the hood down over your
head. Remove the hood after you are safely
away from the aircraft.

Group 4. Safety hoods, located on the back
of the seat in front of you, have been provided
for your added protection in the event of an
emergency. They are to be used only in the
event of an emergency evacuation, or upon di-
rection of a crew member. The stewardess will
now demonstrate their use. To remove the hood
from its package, pull up on either red tab.
Open the hood to its maximum size by spreading
the neck seal with your hands and shaking it
out as the stewardess is now doing to fill it with
air, Then quickly pull the hood down over your
head as you would a shower cap. Remove the
hood after you are safely away from the aircraft.

Group 5. Safety hoods, located on the backs
of the seats in front of you, have been provided



Taste 6—SEPTAL HOOD—MALE—ELEVATED TEMPERATURE—RESTING

SUBJECT #17 Age: 20 Surface Area: 1.91 Sq.M Temperature: 58°C Hood #000523
: TIME—MINUTES
0 1 2 3 4 5 5.45,

+03 2.2 3.5 6.1 8.3 9.0+ 9.04
20.9 20.0 18.1 15,1 12.6 10.4 10.2

96 96 82 88 90 96 90
16 4 12 8 10 13 16
SUBJECT #15 Age: 28 Surface Area: 1,83 Sq. M Temperature: 56°C Hood #000499
0 1 2 3 3.90

2.6 4.0 5.8 71
19.6 17.8 15.9 14.5

— 80 84 87 90
— 7 8 12 14
SUBJECT #18 Age: 25 Surface Area: 2.12 Sq. M Temperature: 56.5°C = Hood #000527
0 1 2 3 4 5.08

2.1 4.1 TA 7.9 9.04
19.4 17.9 13.8 14 9.5

74 72 74 78 82 :
12 12 il 12 14 ,
SUBJECT #32 Age: 22 Surface Area: 1.77 Sq. M Temperature: 59.5°C Hood #000525
0 1 2 3.03

03 3.1 6.4 6.4
20.9 18.4 16,1 14,4

76 80 70 76
— 10 9 9
SUBJECT #33 Age: 25 Surface Area: 2.18 Sq. M Temperature: 57°C Hood #000527
0 1 2 3 3.13

3.0 4.9 6.2 6.8

19.8 15.7 11.9 10.8
84 82 88
13 il 17

40




Retention of Information. ‘The overall reten-
tion rate of the safety information presented
was a respectable 73%, while the retention rate
for specific questions ranged from approximately
30% to 100%, It seems significant that demon-
stration of items did not seem positively to in-
fluence the amount of information retained.
This suggests that either present techniques of
demonstration could be improved, or that the
passive attitude of the passenger in receiving
the briefing information limits retention, It is,
however, more important to consider the rela-
tionship between retention of information and
subsequent performance. It may be assumed
(perhaps incorrectly) that subjects who do not
retain much of the information will not be able
to function well with the safety devices. How-
ever, it is not clear that retention of information
about the device will result in adequate perform-
ance with it. In fact, subjects were almost. per-
fect. in their responses to the question about how
to distend the hood fully; but, as noted above,
this activity was a main source of inefficiency in
hood-donning. In other words, retention of spe-
cific bits of information per se is probably of
little significance in evaluating briefing effective-
ness. Instead, there is a trend for greater under-
standing of what kinds of experience have the
greatest influence upon passengers’ subsequent

30

performance with safety devices, whether they
be briefings or practical exercises.

Finally, it appears that women have greater
success than men in donning hoods. This is a
replication of previous findings' and might be
accounted for by prior experiences with bathing
caps and hair nets, activities foreign to most
men. There have as yet been no suggestions
about how to share this experience with males.

Recommendations. In sum, the following rec-
ommendations would seem warranted on the
basis of the data obtained in this experiment:

(1) General safety briefings should probably
contain more information about use of safety
devices.

(2) The portion of the briefings dealing with
safety hoods should include some mention of the
adequacy of the air supply.

(8) The opening in the hood’s elastic neck
seal should be modified to make it easier to find.

(4) Consideration should be given to using a
larger, less compact hood package, with possible
enclosure of self-distending devices.

(5) Further consideration should be given to
developing practical ways in which passengers
could obtain first-hand experience with safety
devices.



LIST OF CONTRIBUTORS

Patsy R. Fowler, M.S. Physiologist, Stress Physiology Research
Physiology Laboratory
Civil Aeromedical Institute

Harry L. Gibbons, M.D. Chief, Aeromedical Research Branch
Civil Aeromedical Institute

Mark F. Lewis, Ph.D. Chief, Visual Processes Research
Psychology Laboratory
Civil Aeromedical Institute

Ernest B. McFadden, M.S. Chief, Survival Equipment Research
Protection and Survival Laboratory
Civil Aeromedical Institute

Jess M. McKenzie, Ph.D. Chief, Stress Physiology Research
Physiology Laboratory
Civil Aeromedical Institute

James M. Simpson Human Factors Technician
Protection and Survival Laboratory
Civil Aeromedical Institute

Roger C. Smith, Ph.D. Chief, Clinical Psychology and
Learning Processes Research
Psychology Laboratory
Civil Aeromedical Institute

Jerry V. Tobias, Ph.D. Chief, Communications Processes Research
Psychology Laboratory
Civil Aeromedical Institute


SECTION III
OPERATIONAL CONSIDERATIONS


I

TaBLE 5.—Time required for Carbon Dioxide Concentration to Reach 5% in the Septal Hood, Carbon Dioxide within
the Drawstring Hood and Oxygen Concentration, Percent of Leakage for Both Types of Hoods at this Time is also
Presented.

Subject Time To % CO» In % Oe % Leakage
Subject Area 5% COz DRW At

Group Sex Number  (M?)_—s'In Sept. This Time Sept. Drw. Sept. Drw.
Rest M 1 1.93 3.18 3.8 14.0 17.6 0.4 62.4
Cool 3 1.94 3.55 3.2 13.5 16.1 0.5 50.1
4 1.89 4.32 2.7 13.8 18.3 1.0 73.8
6 1,83 3.18 3.5 13.2 17.2 3.0 46.4
7 1.87 4,50 29 13.9 16.7 0.4 62.1
F 2 1.71 4,32 2.6 14,2 18.7 0.9 66.8
#39 1.44 5.00 4.4 15.7 15.0 6.6 42.8
28 1.51 4.32 1.8 14.6 19.2 1.5 87.3
29 1.57 2.92 3.0 15.5 17.5 3.6 57.5
5 1,56 4.47 2.8 13.1 18.5 0.2 74.7

MEAN + S.E.M. 3.97 & .23 14,15  .28 1.81 + .64
Exer. M 9 1,89 1.83 4,1 14.0 17.0 0.6 87.7
Cool 12 1.99 1.43 2.8 15.5 17.9 0.0 59.8
31 1,83 1.70 2.8 13.5 16.7 1.2 69.0
27 2.01 1.50 1.5 14,6 19.1 1.2 71.4
30 1.91 1.03 2.6 16.2 17.7 1.2 70.4
F 13 1.69 2,08 6.7 11.5 12.7 0.2 15.3
8 1.73 2.87 3.1 15.1 17.6 0.2 60.8
ul 1.61 2,52 4.7 15.1 12.6 0.2 32.7
10 1.64 2.12 27 11.7 17.6 0.4 63.6
36 1.56 1.67 3.0 13.8 17.7 1.0 27.1

MEAN + S.E.M. 1,85 4 .15 14.10 + .49 62 + .15
Rest M 15 1.83 3.80 5.8 14.5 15.5 0.5 53.6
Heat 33 2.18 2,10 2.8 15.3 18.7 Ld 45.7
17 1.91 2.48 3.0 16.1 18.2 0.0 54.9
18 2.12 2.60 4.3 15.7 16.5 0.3 32.7
32 1.77 2.37 2.9 15.3 18.0 3.8 56.8
F 14 1.84 2,92 2.9 17.3 17.3 1.8 65.3
16 1.76 3.07 3.1 15.4 17.3 1.8 60.2
#19 1.32 3.08 3.8 16.9 17.9 0.0 36.6
20 1,52 4.08 2.8 14.9 18,1 2.3 38.5
*40 1.54 4,00 3.4 15.3 17.4 20.9 67.4
MEAN + S.E.M. 2.94 + .22 15.71 + .30 1.29 4 . 426
Exer. M 21 1.86 0.78 3.9 17.7 17.8 0.0 20.1
Heat 22 1.96 1.37 2.3 16.4 18.4 0.0 37.2
23 2.05 1,22 3.0 12.6 17.2 0.3 32.4
24 2.12 0.95 3.3 17.6 16.7 0.3 10.7
25 1.87 1.23 3.2 12.3 18,2 1.0 63.0
F 435 1.74 1.58 1.4 15.0 17.8 1.2 71.3
34 1,63 1.57 2.2 14.8 18.8 0.9 73.7
#26 1.65 1.77 3.4 13.0 16.8 1.3 61.9
37 1.73 1.65 3.3 13,2 17.8 1.3 52.8
38 1.43 1.83 3.4 15.7 16.8 15 64.5

MEAN + S.E.M. 1.40 + 11 14.83 + 64 78 4.18

*Indicates long hair.
*#* Subject 40 (long hair) not included.

13


SECTION II
SENSORY EFFECTS



pected to provide absolute protection and life-
support for indefinite periods. For example, the
data in Table 5 indicate that a carbon dioxide
concentration of 5% was reached in Type S hoods
within 14 to 4.0 minutes, depending on the
temperature and degree of physical exertion. A
projection of these data to 8%, the generally
accepted maximum allowable concentration, is
shown in Table 7.

Apparently, work output and, to a smaller
degree, ambient temperature are important fac-
tors modifying the time available to an eyacuee
wearing this hood. Little information is avail-
able on the effects of low concentrations (1%-
8%) of carbon dioxide on psychomotor efficiency
or on the incidence in the flying population of
idiosyncrasies to the gas. An exhaustive search
of the medical literature yielded no information
of this type. Reports of experiments with CO,
concentrations above 8% are available; these in-
dicate a compromise of psychomotor efficiency.
This concentration of carbon dioxide, therefore,
should be taken as the maximum acceptable con-
centration for the hood.

TaBLE 7.—Time to Reach 8% CO2 (Min.)*

Conditions Rest Exercise
Cool. - 6.4 3.0
Heat _ - 4.9 2,2

*Calculated from mean time to reach 5%

No data are available on the metabolic rates
of semi-hysterical people attempting to escape
a burning aircraft, but there is no reason to
expect that oxygen consumption under such con-
ditions would exceed those of our exercising
subjects. Therefore, the 8% tolerance time of
approximately 120 seconds obtained for this
group seems a conservative estimate of the time
during which the average evacuee could benefit
from the hood.

It is concluded, on the basis of the data ob-
tained with pentane, that the wearer of the Type
S hood is given excellent fume protection. This
type of extrapolation is commonly employed by
those who evaluate such devices, but a few small
caveats are worth noting. Practical considera-
tions dictated that. these tests be confined to the
study of a single substance as a leakage “model”
and pentane was chosen as a compromise between

15

eee

gases of higher and lower molecular weight, fat
solubility, and other chemical properties, and
because it is reasonably safe for tests at concen-
trations up to 1.4% (flammability limit). How-
ever, toxic gases with greater diffusion potentials
than pentane may occur in aireraft fires (e.g.,
HCN, CO, aldehydes, HCL); these findings
must therefore be considered only as approxi-
mations of safety limits.

It should also be noted that, even with the best
manufacturing controls, maintenance, etc., a de-
vice may occasionally fail to give protection.
That this may occur with the best of designs is
illustrated by an incident which occurred during
an earlier test. An experienced investigator,
wearing approved (Bureau of Mines) full-face
regalia with air supply, became incapacitated by
a leakage of lachrymator gas while serving as a
safety man for another investigator who was
wearing a Type S smoke hoood. The man
equipped with the hood discovered the accident
and led the visually incapacitated “safety man”
from the chamber. Such experiences with ap-
proved rescue equipment are rare, but serve to
point up the possibility that even the best. devices
may occasionally fail.

Furthermore, aside from a slight risk of leak-
age, individuals who, for various reasons, are
abnormally insensitive to carbon dioxide, may
suffer from insidious hypoxia when the oxygen
is consumed; normal individuals will be forced
to remove the hood by the sensation of suffoca-
tion which carbon dioxide normally evokes.
Although a few accidents due to carbon dioxide
hyposensitivity have been reported (e.g., in
underwater swimmers), medical reports on the
subject indicate that the incidence of dangerous
hypoxia in those wearing the hood would be
rare; in the present studies none of the 40 sub-
jects exhibited any clear-cut signs of hypoxia.

The small risk of hypoxia becomes smaller still
in comparison to the alternative of breathing a
super-heated atmosphere containing mixtures of
highly toxic gases. Those who are not killed
outright by such an environment, risk pulmonary
damage leading to a permanent debilitating
respiratory distress.

It is concluded that the Type S hood is a
simple, effective device which will increase the
probability of survival from an aircraft fire.





*%& HOOD
SAMPLE

kk

DRAWSTRING
HOOD ON

Occ PENTANE
INJECTED

+
|

Ficvre 5.
D hood and exposure.
of 824 ppm. Rev

Stars denote hood samples.

celerate exponentially as equilibrium was ap-
proached. A simple evaluation of detector sensi-
tivity, however, demonstrates the minor signifi-
cance of this possibility. As the effect of wearing
perfumes, after-shave lotions, etc., on detector
response was unknown, 1-2 microliters of “Royal
Secret” bath perfiune were placed into a clean
hood and the air inside subjected to analysis.
This amount of perfume, significantly less than
the amount estimated to be worn by the average
young lady, produced detectable responses, It

sed to provide left-to-right reading.

10

4

3
TIME (MIN.)

Scale copy of sample record of ionization detector responses to pentane in alternate samples from Type
Note progres

PLR PRA

4

4

~

tt HOOD OFF

ve leakage to near chamber concentration

was concluded from this, as well as from cali-
bration data, that any leakage of practical sig-
nificance would be detected and that any
absorption by the body of concentrations below
those levels would not be significant. To avoid
artifacts due to perfumes, ete., all subjects were
instructed not to use these substances on the day
of the tests.

All hoods were numbered and an attempt was
made to distribute them in a random fashion
throughout all four experimental groups. As



TasiLE 16.—DRAWSTRING HOOD—MALE—ELEVATED TEMPERATURE—EXERCISING

SUBJECT #21 Age: 22 Surface Area: 1,86 Sq. M Temperature: 59°C Hood #000239

TIME—MINUTES
0 1 2 3 4 5 6 6.18

«03 4.9 6.1 6.6 6.7 6.7 6.7 6.7
- 20.9 17.0 13.6 12.3 11.8 12.3 12.3 12.3
154 152 154 162 164 166 176

12 13 18 24 24 26 36
SUBJECT #22 Age: 21 Surface Area: 1.96 Sq. M Temperature: 61°C Hood #000247
0 1 2 3 4 5 6 6.33

-03 2.4 2.2 2.2 2.8 2.8 2.8 2.8
20.9 18.9 18.4 18.3 18.1 17.8 17.5 17.5
108 124 122 122 126 122 126 136

_—_ 18 19 17 18 19 19 20
SUBJECT #23 Age: 22 Surface Area: 2.05 Sq. M Temperature: 62.5°C Hood #000282
0 1 2 2.80

2.8 3.9 6.5
17.5 15,3 13.5
108 128 140

12 16 26
SUBJECT #24 Age: 22 Surface Area: 2,12 Sq. M Temperature: 60°C Hood #000380
0 1 2 3 4 4,53

6.7 6.7 6.7

16.4 11.0 9.0 8.9 8.9
126 134 142 160 164
20 29 37 40 42

SUBJECT #25. Surface Area: 1.87 Sq. M Temperature: 60°C Hood #000361

0 1 2 3 4 5 6 6.25

03 3.2 3.3 3.9 3.3 3.3 3.3 3.3

20.9 18.7 17.9 17.7 17.4 17.9 18.1 17.6
106 108, 120 122 128 134 140 144
16 4 9 9 13 12 12 22

50




Chapter 4.

Smoke Hood Tests: Acoustic Attenuation®

Jerry V. Tobias, Ph.D.

I. Introduction.

During aircraft evacuation studies, the ques-
tion arose of the protective smoke hood’s possible
interference with speech. If the hood blocks
much sound, passengers will have difficulty hear-
ing instructions from the aircraft crew. A study
was done to determine the extent to which the
smoke hood acts as a barrier to the transmission
of sound.

II. Method.

The procedure followed American Standard
Z24,22-1957, “American Standard Method for the
Measurement of the Real-Ear Attenuation of Ear
Protectors at Threshold,” * except that thirty
subjects (men and women between the ages of
21 and 50) were given two experimental trials

*The a ance of R. Lance Christie during the con-
duct of this study is gratefully acknowledged.

o -10
Uv
c
c
i) ie}
=
3 4
2
c
2
= 10
a
2 3 100 2 5 1000 a 5 10000 2
Frequency in Hz
Fieure 1. 30 subjects’ free-field threshold is plotted as zero line. Standard experimental variation in audiometric

experiments is plus or minus five decibels,
the smoke hood on, as compa

23

‘The curve represents the free-field threshold of the 30 subjects with
ed to their threshold without it.


APPENDIX B
Part 5. Briefing Questionnaire Part II
1. Do you think that the instructions given you would tend to raise your anxiety or make you feel
uneasy prior to an actual flight?
Yes _______No
If you answered yes to question 1, what was it about the instructions that would have that effect?
(Check as many as are applicable)
(a) The language of the instructions.
(b) The pointing out of possible emergencies.

(c) The amount of material presented.
(d) Other factors? (Please explain below.)

2, Have you ever flown in any aircraft before? _________Yes _______No

If the answer to question 2 is yes, please answer the questions under (a); if the answer is no,
please answer those under (b).

(a) For those who have flown before.

(1) What were your reactions prior to your first flying experience? (Please mark the point
on the scale below which best describes your feelings.)

Extremely Moderately Some anticipation Moderately Completely
tense and tense and and excitement. at ease at ease
uneasy uneasy but no fear and relaxed and relaxed

(2)Do you want to fly again?

Will never Would not Don’t care if Would like Will fly

fly again like to T fly again or to fly again again
fly again not
(3) How do you think you would feel prior to your next flight if it was to be on a commercial
airliner?
Extremely Moderately Some anticipation Moderately Completely
tense and tense and and excitement at ease at ease
uneasy uneasy but no fear and relaxed and relaxed

(b) For those who have not flown.

57


OO

(c) Pull cover open, lift the top and bottom parts in and set it aside.

(d) Pull the cover open on the top, pull the red handle inward and up, and holding the bottom
of the window, lift it in and set it aside.

9. In a water landing you are supplied (G6 only)

(a) A life jacket.

(b) A flotation cushion.

(c) A life raft.

(d) A life jacket and flotation cushion.

10. To put on a life jacket (G6 only)

(a) Put it around your body and snap the neck fasteners.

(b) Pull it over your head.

(c) Put it around your waist and fasten the top straps.

(d) Put it over your head and fasten the rear straps to the front.

11. To inflate the life jacket. (G6 only)

(a) Pull the red handle.
(b) Put it on, it will inflate automatically in the water.
(c) Pull the two black knobs.

12. To take out the flotation cushion (G6 only)

(a) Tilt the seat back, then pull the front up.
(b) Pull up on the front and rear at the same time.
(c) Take hold of the rear of the cushion and pull it forward.

13. Individual oxygen masks are for use if

(a) There is a crash.

(b) There is fire and smoke.
(c) The cabin loses pressure.
(d) Your stomach gets upset.

14, If an oxygen mask drops in front of you, you should
(a) Extinguish all cigarettes, grasp the cup, pull it to your face, place it over your nose and
mouth, and breathe normally.
(b) Pull the cup to your face, put it over your nose and breathe normally.
(c) Pull the cup to your face, place it over your nose and mouth, and breathe normally,
(d) Wait for a stewardess to give instructions.

15. Safety hoods are located

(a) Under your seat.

(b) In the compartment above your seat.
(c) In your headrest.

(d) In the back of the seat in front of you.

59


16. Safety hoods are for use

(a) When oxygen level drops.
(b) When an emergency evacuation is required.
(c) When you feel airsick.

17. To remove the hood from its package and open it you (G2 thru G6 only)

(a) Pull the red tab and unfold the hood.

(b) Pull the red tab and spread the neck seal with your hands.

(c) Pull the red tab and put the hood over your head quickly.

(d) Pull the red tab, unfold the hood, pull it quickly over your head.

18. To fill the hood with air you (G3 thru G6 only)

(a) Pull it quickly and hard over your head.
(b) Unfold it and blow in it.

(c) Put it over your head and fluff it out.

(d) Shake it out.

19. If you wear glasses the easiest way to put on the hoods is (G5 & G6 only)

(a) To pull it over your chin, then back over your head.

(b) ‘To stretch the seal as far as it will go pulling it over your head.

(c) To put it on the back of your head, then pull it over your glasses by stretching it with your
hands.

(d) By putting it on like a shower cap.

20. You should wear your hood, if needed, until

(a) The stewardess tells you to take them off.
(b) You can barely breathe.

(c) You can no longer see any smoke.

(d) You are safely away from the aircraft.

21. When taking off you should
(a) Fasten your seatbelt, put out your cigarettes, and bring your chairback and your tray tables
upright.
(b) Fasten your seatbelt, and bring your chairback and tray table upright.
(c) Fasten your seatbelt, put out your cigarettes, and bring your tray table upright.
(d) Extinguish your cigarettes, and bring your chairback and tray table upright.

60


runs to reduce fogging. For four of the subjects,
four additional runs were made at the conclusion
of the test session in which the subjects were
instructed to view through the aluminized por-
tion of the hoods.

Ill. Results.

Table 1 shows the optical transmission of the
smoke hood samples; each value is the average
of four determinations made by each of four
observers for each test: patch.

Figure 1 shows the frequency of correct re-
sponse for all subjects as a function of the deci-
mal acuity required to identify the test targets
under emergency illumination with and without
hoods. These data indicate the acuity is reduced
under emergency illumination to 0,68; with clear
smoke hoods (Type S), acuity is further reduced
to 0.55; and with aluminized hoods (Type D),
reduced beyond the measurement capacity of the
tests employed.

TaBLE 1.—Optical Transmission of Test Patches

Test Patch Transmission Density Comment

Lees eee 79.7% 0.0985 Patch from edge of
uncoated sample.
Qe 30.3% 0.0953 Patch from center
of uncoated sample
Beeeeeee ee 80.1% 00964 Patch from edge of
uncoated sample.
Ale 76.2% 0.118 Clear area from
aluminized sample.
Blo... 75.1% 0,124 Clear arca from
aluminized sample.
om 11.1% 0.955 — Aluminized pateh.
D 11.3% 0.947 Aluminized pateh.

Table 2 shows the decimal acuity of each
subject under all conditions, For each subject,
acuity was reduced under emergency illumination
and progressively reduced with clear and
aluminized smoke hoods.

o—o No hoods n=l2

%—% Clear hoods n=12

e--e Aluminized hoods n=ll

SN

N == S§
pve---g---- eee

8 1.0 1.2 1.4

DECIMAL ACUITY

w Or &
2)
Zz
fo)
a
wn L
wy 8
x
—
0 e
Wd
we -6F \
oe \
ro) \
oO \
uo L \
o -4t \
\

3 \
Zz \
W =
we .2
Co
uJ
a
w

T T

2 4 6
Fiore 1.

Frequency of correct test target identifications for all subjects with and without hoods under emergency

illumination.

20


The Development of a Protective Passenger Smoke Hood

Ernest B. McFadden, M.S.

Introduction

Investigation of a number of recent transport.
aircraft accidents has indicated the need for pro-
tection of passengers and crew from the effects
of toxic fumes, smoke, and flame. Of paramount
importance is the protection of the human
respiratory system and maintenance of the occu-
pant in a conscious and mobile state so that
evacuation may be accomplished before elevated
temperatures render the cabin uninhabitable.
This report describes the evaluation of a “get-
me-out” device designed to provide protection
of the respiratory tract from the effects of toxic

Type D (drawstring) protective hood.

Fieure 1.

ELASTIC
POLYURETHANE
SEAL

Ficcre 2. Type S (septal) protective hood.
smoke and fumes. In addition, the device, a
polyimide hood which encloses the head, provides
some degree of flame protection. A report on a
preliminary version of this hood has already been
published*; therefore, the concern of this report
is with subsequent evaluations of this device.
Studies carried out by the Aerospace Indus-
tries Association’, as well as the FAA Flight
Standards full-scale evacuation tests’, revealed
specific design deficiencies in the original proto-
type (Figure 1). Although aluminization of the
polyimide surface provided excellent radiant heat




%*& HOOD
SAMPLE

Bethel ind bed bd End edd dled dd edie

SEPTAL ERE RE PEE PEPE EP EDI PED ED EDT a
HOOD ae t + Ft F

lOcc PENTANE 2 8 4 HOOD OFF

INJECTED TIME (MIN.)

Ficure 6. Scale copy of sample record (reversed to facilitate reading) of detector response to pentane in exposure
chamber and Type S hood. Note absence of leakage in presence of 324 ppm.

11


SECTION I
ENVIRONMENTAL PROTECTION


Chapter 2.

Smoke Hood Effectiveness in a Toxic Environment

Ernest B. McFadden, M.S.
Harry L. Gibbons, M.D.

I, Introduction.

The primary purpose of this study was to
determine the effectiveness of the Type S pro-
tective smoke hood in preventing inhalation of
toxic substances similar to those produced in the
combustion of aireraft fuel and cabin interior
materials. This report describes an experimental
procedure wherein subjects were subjected to a
toxic environment. resulting from combustion of
JP-4 and water-soluble oils. The test exposed
subjects to an environment filled with heavy
black smoke consisting of significant quantities
of carbon monoxide and soot particles. Since
the affinity of blood for carbon monoxide is well
known (being several hundred times greater for
carbon monoxide than for oxygen), and it is
more easily passed through membranes due to
its relatively small molecular size, it is especially
important that the hood prevent inhalation of
this gas. By blood samples, following exposure,
it will be possible to determine the capability of
the hood to protect the wearer from this type of
toxic gas.

Il. Methods.

Dense black smoke was produced in a large
generator from the combustion of JP-4 and
water-soluble oils. Carbon monoxide concentra-
tions ranged from 450 to 950 ppm. Combustion
was controlled by limiting the amount of oxygen
available in order to produce these concentrations
of carbon monoxide. Output of the generator
was forced into a specially constructed smoke
chamber (Figure 1). An octagonal maze was
constructed, which consisted of eight separate
lanes. The maze was designed to increase physi-
cal exertion and task complexity, so that per-
formance under smoke conditions could be
quantified and evaluated. At the end of each
maze a switch and switch box were located.
Each subject donned a Type S smoke hood,

W

entered the maze, and was required to locate the
first switch to his left in the dark black smoke
and complete an on-off switching cycle. The
subject then proceeded to the next station and
completed a similar switching operation, pro-
gressing around the octagonal maze in a clock-
wise direction. In this way, external and internal
safety observers could follow the subject's pro-
gress and be aware of his location in the smoke
chamber at all times. The subjects continued to
traverse the mazes until they had been subjected
to at least a ninety-second exposure to the en-
vironment while wearing the hood.

Seven adult volunteer subjects (four male,
three female) participated in this study. Due
to the hostility of the environment, all subjects
were exposed only while wearing hoods.

UI. Results.

‘There was no evidence of change between blood
carbon monoxide concentrations in five of seven
subjects, as is shown in Table 1. Subject 6
smoked a cigar shortly before the tests (although
all subjects were requested to refrain from smok-
ing for one hour prior to the tests), and it was
determined during a post-exposure interview
that his pre-exposure blood sample was taken
shortly after his smoking the cigar. Since his
blood carbon monoxide level was /ower following
the experiment than before it, it would appear
that he had eliminated a considerable amount of
carbon monoxide during both the pre-test. wait-
ing period and the test itself. One female sub-
ject showed an increase in carbon monoxide
saturation; however, the change was slight and
of no significance as far as the final degree of
saturation achieved. Furthermore, there was no
subjective evidence of significant hood leakage,
as she could not recollect smelling smoke or
fumes within the hood when questioned follow-
ing the experiment.



te

AM 70-20

PROTECTIVE SMOKE HOOD STUDIES
Edited by
Ernest B. McFadden, M.S.
Roger C. Smith, Ph.D.
Approved by Released by
°o
Bhat Rte (UV Skgek 0
J. Roserr Diniz, M.D. P. V. Stecer, M.D.
Crier, Crvin ArromEpICAL Frorrat Air Surcron
InstTITUTE

December 1970

Department of Transportation

FEDERAL AVIATION ADMINISTRATION
Office of Aviation Medicine


Tasie 2.—SEPTAL HOOD—MALE—NORMAL TEMPERATURE—RESTING

SUBJECT #1 Age: 25 Surface Area: 1.93 Sq. M Temperature: 26°C Hood #000489
TIME—MINUTES
0 1 2 3 4 4.18
2.5 4.1 47 5.6 5.8
18.5 16.4 14,2 12,0 1.8
dit 97 111 92 114
i 9 12 16 18

Surface Area: 1.94 Sq. M

‘Temperature: 26°C

Hood #000513

1 2 3 4 4,20
2.0 3.2 5.2 5.6 5.7
19.7 17.6 14.7 12.6 12,3
80 75 78 89 95
4 4 13 16 20

Surface Area: 1.89 Sq. M

‘Temperature: 26°C

Hood #000493

1 2 3 4 4.32
17 3.2 4.0 4.5 6.5
19.5 17.5 15.7 13.8 16.9
72 72 74 74 72
4 14 14 15 18

SUBJECT #6 Age: 27 Surface Area: 1.83Sq.M Temperature: 25.5°C Hood #000527
0 1 2 3 4 4,20
Bl 42 490 58 8
182 15.7 18.5 11.2 10.8
72 i 78 87 90
u u 12 4 18
SUBJECT #7 Age: 24 Surface Area: 1.87 Sq.M Temperature: 25.5°C Hood #000482
0 1 2 3 4 4,50
+03 2.4 3.8 4.2 4.7 5.0
20.9 19.0 17.3 15.9 14.3 13.8
61 58 55 58 60 62
ul 16 18 19 20 20

36



approximately the tenth to eleventh rib. The
impedance pneumograph provided a method of
continuously monitoring the respiratory rate,
and gave estimates of relative tidal volume.

All electrical apparatus were grounded.

Oxygen consumption and carbon dioxide pro-
duction were measured continuously by drawing
a stream of gas from the hood and passing it
through a Beckman Infra-Red Carbon Dioxide
Analyzer, Model LB-1, and a Beckman Oxygen
Analyzer, Model F3M3-1A3A. The ECG, im-
pedance pneumograph, and carbon dioxide sig-
nals were recorded on an E and M Physiograph
Six Recorder using appropriate pre-amplifiers.
Oxygen concentrations were recorded on a Brown
Electronik, Series SY strip chart recorder.

Calibrations of the infra-red carbon dioxide
and paramagnetic oxygen analyzers were con-
ducted before and after the day’s tests and when-
ever chamber temperature was changed.

The system for measurement of hydrocarbon
concentration is also illustrated in Figure 1. The

PARAMAGNETIC

technical aspects of this system will be presented
in a later report.

Loss of air during the experiment can be
computed from the flow through the respiratory
gas analyzers (132.1 ml/min) and flow into the
hydrocarbon analysis system. As the total flow
through the latter was shared equally by hood
and exposure chamber, loss from the hood during
each test was 132.1 + 42.25, or 174.35 ml/min.
During a six-minute experiment, for example,
an approximate volumetric change of 1046 ml,
or 5% of the starting hood volume (approxi-
mately 20 liters), was obtained.

Iii. Results and Discussions.

Heart rate and respiratory changes seen during
these tests were consistent with those known to
be induced by exercise and/or carbon dioxide
accumulation (see Appendix B, Tables 2-17).
Heart and respiratory rates generally increased
significantly during exercise, but as anticipated,
the most marked change in respiration was the

OC VACUUM
PUMP

SAMPLING LOOP
Pa

PHYSIOLOGICAL
MONITORING

EXPOSURE CHAMBER

Fieurr J.

HOOD SAMPLING LINES SAMPLING
L VALVE
—TM —~ >
Oe &>
3-WAY SOLENOID vonizarvon )
vane DETECTOR
CHAMBER SAMPLING LINE (Ha FLAME)

SAMPLING
LOOP

NITROGEN TANK

The experimental set-up for measuring physiological changes, respiratory gases, and hydrocarbon leak-
age during exposure to pentane fumes of human subjects wearing protective hoods.
system, samples of air from hood or chamber enter the gas train alternately via the

In the pentane detection
Way solenoid valve. The

sampling valve, operating simultaneously, turns 90° to switch sampling loops from the sample-vacuum pump

line to the nitrogen detector line.


Chapter 1.

Evaluation of Leakage in Protective Smoke Hoods

Jess M. McKenzie, Ph.D.

Ernest B. McFadden, M.S.

James M. Simpson

Patsy R. Fowler, M.S.

I. Introduction.

This report. presents the results of experiments
designed to answer two important questions re-
lating to the smoke hood: (1) what are its life
support capabilities with respect to quality of
the contained air supply and to the metabolic
rate of the wearer; and (2) which of two styles
of neck seal is more efficient in preventing
leakage?

II. Methods and Procedures.

The two types of protective hoods evaluated
were essentially identical except for the neck
seal: Type D hoods possessed a drawstring seal,
while the Type S hood had a septal (membrane)
seal of heat-resistant urethane which fits closely
but not uncomfortably about the neck. Ten*
hoods of each type were tested. Each was used

Tasxe 1.—Conditions of the Experiment
Physical Exertion

‘Temperature
Rest Exercise
26° C 5 Male 5 Male
(78. 8° F) 5 Female 5 Female
60° C 5 Male 5 Male
(140° F) 5 Female 5 Female

at least once and some were used as many as six
times in order to evaluate the effect of multiple
use. All hoods were obtained directly from the
G. T. Schjeldahl Company and were not worn
prior to testing.

* One Type S hood (#482) was destroyed after only
one trial; another new hood replaced it. Thus, eleven
hoods of this type were used (see Table 2).

Conditions for the tests were varied according
to a block design (Table 1).

The twenty male and twenty female subjects
(described in Appendix A, Table 1), none of
whom had any previous experience with the de-
vice, were divided equally among the four groups
(see Table 1). Each received, shortly before the
experiment, essentially the same instructions per-
taining to the experimental procedure, donning
and removal of the hood, etc.

Exercise was performed on a Godart bicycle
ergometer, equipped with a magnetic eddy cur-
rent. brake resistance which was set at a constant
load, so that 45 watts (0.06 hp) of power were
generated at 45 rpm. This exercise, which may
be considered as light to moderately heavy, was
performed by all subjects in the appropriate
groups. Subjects who did not exercise during
exposure (rest groups) sat quietly in a chair for
several minutes prior to donning the hoods and
remained seated during the experiment.

Safety considerations dictated that exposure
of subjects to high temperature be limited to
140 degrees F.

Each subject was prepared for physiological
monitoring prior to entering the test chamber.
Adhesive electrodes were affixed to the chest. in
the usual manner. The ground was located over
the sternum in a direct: inter-nipple line, with
one electrode being located approximately 6 to 8
cm directly below the left nipple. This provided
an excellent heart rate signal with minimum
interference due to extraneous bioelectrical po-
tentials developed during exercise.

Impedance pneumograph electrodes were
placed on each mid-axillary line of the chest at


=

Tasie 15.—DRAWSTRING HOOD—FEMALE—ELEVATED TEMPERATURE—RESTING

SUBJECT #40 Age: 26 Surface Area: 1,54 Sq. M Temperature: 60°C Hood #000252

0 1 2 3 4 5 6 7 8 9 9.53

03 1.2 21 3.1 3.4 3.8 4,1 3.4 3.2 3.4 3.4
20.9 19.6 18.7 17.7 17.4 17.4 17.4 17.6 18.2 18.2 18.2

80 78 86 86 84 84 90 94 92 94 94
14 — — 18 16 16 16 18 17 7 il
SUBJECT #20 Age: 27 Surface Area: 1,52 Sq. M Temperature: 60°C Hood #000252
0 1 2 3 4 5 6 6.40

03 1.7 2.4 2.8 2.8 2.8 2.8 2.8
20.9 19.8 18.8 18.3 18.1 18.1 18.1 18.1

86 86 86 83 90 90 94 92
—_ iu 13 13 13 13 12 12
SUBJECT #19 Age: 21 Surface Area: 1.32 Sq. M Temperature: 59°C Hood #000360
0 1 2 3 4 5 6 6.22

.03 2.2 2.7 3.8 3.8 3.8 3.8 3.8
20.9 20.0 18.7 17.9 17.6 17.6 17.3 17.3
106 104 102 100 100 100 100 116

— 13 ll 1 15 15 16 26
SUBJECT #16 Age: 28 Surface Area: 1.76 Sq. M Temperature: 57° C Hood #000329
0 1 2 3 4 5 6 6.28

+03 2.7 2.7 3.1 3.1 3.1 3.1 3.1
20.9 18.6 17.9 17.3 17.2 17.3 17.3 17.3

— 98 80 92 90 91 90 96
—_ 13 14 13 4 13 4 16

SUBJECT #14 Age: 40 Surface Area: 1.84 Sq. M Temperature: 55°C. Hood #000360
0 1 2 3 4 5 6.05

2.2 2.9 2.9 3.0 27 2.8
19,2 17.6 17.3 17.3 17.8 17.8
81 79 79 81 80 88
22 18 17 18 15 18

49


In addition, sound recordings were made by
means of a tape recorder, with the effective
microphone being placed in the middle of the
cabin.

The slide was in place, inflated, and the door
was partially open in order to reduce the vari-
ability induced by crew members’ actions in per-
forming these tasks, and to allow comparison
between individual tes

A protective smoke hood folded in a single
vertical fold was inserted in the seat-back pocket
of each seat prior to passenger boarding. ‘The
Type D hoods were used in this experiment.
Crew members were equipped with hoods of
similar design but lacking the aluminized coat-
ing of the Type D hood. Passengers were ran-
domly seated and the numbers noted by the cabin
attendant after boarding. Passenger location
and seating diagrams for the tests are attached
(see Figure 1).

Before each evacuation in which hoods were
to be used, the cabin attendant gave a brief dem-
onstration of the correct procedure for donning
the hood.

For one group of sixty-four subjects (Group
A), the first evacuation test (Test A1) was car-
ried out with no smoke in the cabin and without
using the hoods. The second test (Test A2) was
carried out with dense smoke injected into the
cabin from fore and aft positions and hoods were
donned by the subjects and worn during escape.
All actions (ie., smoke, hood donning, evacua-
tion, and timing) were initiated upon activation
of an audio alarm system.

The si four subjects in the second group
(Group B) made their first evacuation (Test
B1) under smoke conditions while wearing the
hoods. The second evacuation (‘Test B2) was
made without use of hoods or the presence of
smoke.

To control for the effects of smoke on evacua-
tion independently of the presence of hoods, the
subjects in Group B were evacuated once while
wearing the hoods (Test C1), but without the
presence of smoke.

Smoke was produced by means of a theatrical
smoke generator. It was produced to such an

100 p ©

b
wk

i
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LO
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af
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oy

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5a
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° a a ce ce a Se
SECONDS 9 I0 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
MINUTES 5 1.0 15 2.0 2.5 3.0
TIME

Test A

hin door. » smoke; no hoods

one previous eva

don hoods—initial evacuation experience.

32

Comparison of evacuation flow from a Constellation 749 fuselage of 64 occupants from the aft main
nitial evacuation experience.
ation experience from smoke-filled air

Test A2: Cabin filled with smoke; don hoods—second evacy

‘Test 2: No smoke; no hoods—
ft using hoods, Text ('L: No smoke; don hoods.
tion experience. Best B1: Cabin filled with smoke ;





on

Taste 3.—SEPTAL HOOD—FEMALE—NORMAL TEMPERATURE—RESTING

SUBJECT #2 Age: 25 Surface Area: 1.718q.M ‘Temperature: 26°C Hood #000525
TIME—MINUTES
0 1 2 3 4 4.43
1.9 2.9 4.1 4.8 5.2
20.0 18.8 16.7 14,9 14,2
8 81 8496
15 16 18 24 30
SUBJECT #5 Age: 25 Surface Area: 1.568q.M Temperature: 25.5°C Hood #000509
: 1 2 3 4 4.47
1.8 2.8 3.9 4,7 4.9
19.8 17.9 15.8 13.6 131
Pe ee (0
15 i 13 14 18
SUBJECT #28 Age: 28 Surface Area: 1.518q.M ‘Temperature: 27°C Hood #000515
0 1 2 3 4 4,83
04 23 3.0 45 6.0
20.3 18.3 16.7 15.0 14.3
en
1% OT Vas 24
SUBJECT #39 Age: 21 Surface Area: 1.448q.M ‘Temperature: 26°C Hood #000499
0 1 2 3 4 5 6 7 8 8.50
103 10 18 28 387 60 52 G1 70 ZL
20.9 20.2 19.0 17.9 167 15.7 145 13.5 124 118
68 72—~—«C TH Tk THC BCC
17 16 18 17 16 14 15 15 19 21
SUBJECT #29 Age: 17 Surface Area: 1:57 Sq.M_ ‘Temperature;,27°C — Haod #000513,
0 1 2 3 3,22
103 24 3.6 55 BT
20.9 19.8 17.4 15,2 14.6
84084 i7HCti«iACi(it:«
23 21 21 22 28

37


Tasie 2—Decimal Acuity Under Test Conditions

Normal Emergency Illumination

Mlumination

Clear Hood — Aluminized

Sex No Hood No Hood (Type S$) Hood (Type D)
M 1.33 67 -50 —

M 1.33, .67 .50 _

M 1.33% — .50* .33* _

M 1.33, .80 50 —

M 1.33, . 80 .40 —

M 1.33, 50 50 —

M 1.00%* —.67** . 50** _

M 1,00 67 50 ~

F 1.33 80 67 +25

PF 1,.33** .67** . 50** Off Scale**
M 4.33 67 . 50 Off Seale

KF 1,00* - 50* + 25*

67%

* Corrected with contact lenses
**Corrected with spectacles

21

_ iii_s

IV. Discussion.

Clear smoke hoods (Type S) have optical
transmissions of approximately 75-80 per cent;
these values are similar to the transmission of
optical glass sunglasses. The approximately five
per cent difference between the uncoated samples
and the clear areas from aluminized samples
(Table 1) was probably due to the coating used
to protect the aluminized surface.

These transmissions, together with the data of
Figure 1 and Table 2, indicate that vision in
emergency illumination is so reduced with
aluminized hoods (Type D) as to make such
hoods visually unusable. Visual capacity is sig-
nificantly affected by wearing clear hoods under
emergency illumination, but a 20-25 per cent
increase in the level of emergency illumination
would compensate for the transmission loss
through the non-aluminized hoods.



APPENDIX B

Part 4. Questionnaire Part I

. Were the instructions given by the stewardess clear with respect to use of the safety hoods?

Yes ______No

If your answer is no, please explain why below.

ox

. Please rate the hood as to comfort on the scale below.

|

l
very moderately neither moderately very
uncomfortable uncomfortable comfortable comfortable comfortable
or uncomfortable

. Did you find the hood difficult to put on? .______ Yes _______No

If your answer is yes, please indicate the reasons for your difficulty below.
(a) Getting over hair.
(b) Getting over glasses.
(c) Getting hood off.
(d) Getting hood open.
(e) Filling hood with air.
(£) Spreading neck seal.
(g) Getting out of storage packet.
(h) Other (explain).

Did you have any negative feelings about using the safety hood?
Yes _________No
If your answer is yes, please indicate the reasons below.
(a) Claustrophobic feeling.
(b) Fear of shortage of air.
(c) Reluctance to put “plastic” bag over head.
(d) Began to feel panicky with hood on.
(e) Other (explain).

If you were to be involved in an emergency in an aircraft, do you think you would use the safety
hood if requested to do so?

Yes _________No
56



reflectance and sufficient transparency for ade-
quate vision under normal levels of illumination,
subjects experienced difficulties in vision when
exposed to the .05 foot-candle emergency illumi-
nation as provided in jet transport aircraft.
These evaluations also indicated that: evacuees of
aircraft could not be relied upon to consistently
tighten the drawstring neck seal. Therefore, a
new septal seal was designed which did not re-
quire voluntary tightening to effect an adequate
and protective seal and aluminization of the hood
was restricted to the upper portion of the hood
outside of the range of vision (Figure 2).

In the reports that follow, the primary em-
phasis is upon the septal seal hood (hereafter
called the Type S hood); however, data from
advanced tests of the drawstring seal hood (Type
D) have been included where the findings are
relevant to the overall evaluation of the protec-
tive hood concept. These studies are addressed
to three main points: (1) the degree of protec-
tion against incapacitating agents provided by
the hood; (2) the limitations of the hood in
terms of useful air supply, vision, and audition;
and (3) the utility of the hood. The findings
of these investigations are presented in the fol-
lowing chapters.


only ten hoods of each type were available, there
was an opportunity to evaluate the effects of
multiple use. No apparent effect of repeated
use was noted in Type D hoods, but an obvious
trend toward increased leakage of Type S was
apparent (Table 6). ‘This trend, assumed to be
caused by fatigue of the elastic polyurethane seal,
is an important consideration for future large

scale application: if hoods were to be donned
repeatedly during precautionary evacuations, it
is possible that an undetected compromise of the
seals could occur. This risk can be avoided by
replacing seals after the hoods have been used.
The results of these tests illustrate that no
hood, designed to meet the important criteria of
accessibility and economy of storage, can be ex-

‘TasiE 6.—Effects of Repeated use on Efficiency of Type S (Septal Closure) Hoods

% Leakage at

Hood No. Subject Test Number Condition 2 Minutes
489 M 1 Resting—Cool 0.2
M 2 Exercise—Cool 0.0
M 3 Exercise—Heat Exposure 0.5
M 4 Exereise—-Heat Exposure 0.9
F 5 Exercise—Cool 1.0
493 M 1 Resting—Cool 1.0
F 2 Exereise—Cool 0.4
M 3 Exercise—Heat Exposure 1.0
M 4 Exercise—Cool 2.2
527 M 1 Resting—Cool 0.2
F 2 Exercise—Cool 0.4
M 3 Resting—Heat Exposure 0.0
M 4 Resting—Heat Exposure 1.1
525 F 1 Resting—Cool 0.1
M 2 Exercise—Cool 0.6
Ft 3 Resting—Heat Exposure 0.0
M 4 Exercise—Heat Exposure 1.9
M 5 Resting—Heat Exposure 3.8
F 6 Exercise—Heat Exposure 15
490 M 1 Resting—Heat Exposure 0.5
Fe 2 Exercise—Heat Exposure 1.3
M 3 Exercise—Cool 1.2
¥* 4 Resting—Cool 2.5
515 F 1 Resting—Heat Exposure 0.3
F 2 Resting—Cool 1.2
Fe 3 Resting—Heat Exposure 42.9
513 M 1 Resting—Cool 0.2
F 2 Exercise—Cool 0.3
M 3 Exercise—IHeat Exposure 1.3
F* 4 Resting—Cool 1.3
509 F 1 Resting—Cool 0.2
F 2 Exercise—Cool 0.2
F 3 Resting—Heat Exposure 0.3
F 4 Exereise—Heat Exposure 1.3
506 F 1 Resting—Heat Exposure 0.3
M 2 Exercise—Cool 1.2
523 M 1 Resting—Heat Exposure 21
M 2 Exercise—Heat Exposure 0.3
Fe 3 Exercise—Heat Exposure 1.2
482 M lonly —_Resting—~Cool 0.2

* Indicates long hair.

14


lr

TasLe 13.—DRAWSTRING HOOD—FEMALE—NORMAL TEMPERATURE—EXERCISING

SUBJECT #8 Age: 25 Surface Area: 1.73 Sq. M ‘Temperature: 26°C Hood #000252
~ —_ TIME—MINUTES oo
0 1 2 3 4 5 6 6.23
23 Bl Bl 32 32 32 32
18.7 17.5 «17.5 «17.6 «17.6 17.517.
7 135 146 143 149 151 144
19 3B O8Hi(itiT BOG
SUBJECT #13 Age: 22 Surface Area: 1.69 Sq. M —‘Ttemperature: 25°C Hood #000239
0 1 2 2.50 -
3.9 67 80
17.8 13.0 10.4
114 126 112
15 22 24
SUBJECT #11 ‘Age: 24 Surface Area: 1.61 Sq. M Temperature: 26°C Hood #000247
0 1 2 3 3.17
B40 4.30 BO 5.O
171 13.9 11.8 11.8
138 125 132
12 18 23
SUBJECT #10 Age: 27 Surface Area: 1.64 Sq. M ‘Temperature: 26°C Hood #000380
—_ 0 1 2 3 4 5 6 6.18
26 26 33 3.0 36 36 3.0
19.0 17.7 17.3 17.4 17.4 16.9 16.9
96 105 116 121 125 128
20 22 22 24 24 24

SUBJECT #36 Age: 22 Surface Area: 1.56Sq.M ‘Temperature: 27°C Hood #000270
0 1 2 3 3.68
08 22 33 43 44
20.9 19.8 16.9 15.4 14,7
82 102 18 120 96
3 20 18 2% 2%

aT


APPENDIX B
Part 2. Briefing for Group 6

We would like to welcome you aboard Inter-
national Flight #49, nonstop jet service from
Oklahoma City to Chicago. Our flying time
will be approximately 1 hour and 45 minutes
and we will be flying at an altitude of approxi-
mately 28,000 feet.

We would like to take a moment to point out
the safety features of this aircraft. There are
two exit doors in the forward cabin and two in
the aft cabin, all equipped with slides. In addi-
tion, there are four window exits over the wings.
To use the door mounted slides, lift the door
handle up and push the door out, the slide will
then automatically fall out. Pull the red handle
on the slide to inflate it. It will then be ready
to use.

The window exits are operated by pulling the
cover open on top and grasping the red handle
inside. Pull the handle inward and down. After
grasping the handle and the bottom of the win-
dow, lift the window in, discarding it on the seat
in front of the window area.

In the event of a water landing several safety
devices are provided for you. Your life jacket
is located under your seat. It fits over your head
and the rear straps are fastened to the front and
tightened. It is inflated after leaving the air-
craft by pulling on the two black knobs. In
addition, the cushion you are sitting on is de-
signed to keep you afloat. Grasp it at the rear,
pull it forward, and take it with you.

54

Individual oxygen masks are located in the
compartment above your seat. In case of any
rapid change in cabin pressure, an oxygen mask
will drop down in front of you. Extinguish all
cigarettes, grasp the cup, and pull it to your face.
Put it over your nose and mouth, and breathe
normally.

Safety hoods, located on the back of the seat
in front of you, have been provided for your
added protection in the event of an emergency.
They are to be used only in the event of an
emergency evacuation, or upon direction of a
crew member. The stewardess will now demon-
strate their use. To remove the hood from its
package, pull up on either red tab. Open the
hood to its maximum size by spreading the neck
seal with your hands and shaking it out as the
stewardess is now doing to fill it with air. Then
quickly pull the hood down over your head as
you would a shower cap. For those of you wear-
ing glasses you may find it easier to put the hood
on the back of your head first, then pull the
opening of the seal forward, stretching it to
clear your glasses as the stewardess is now dem-
onstrating. Remove the hood after you are safely
away from the aircraft.

Please fasten your seatbelts now, and observe
the no smoking sign until the captain turns it
off. Also bring your chair backs and tray tables
to an upright position for take-off.

We hope you have a pleasant flight. If we can
do anything to make your trip more comfortable,
please don’t hesitate to call upon us.


TaBLE 1.—Problems Encountered in Hood-Donning,

a

as Judged by Observers, for Each Briefing Group

Group
qi G2 G3 G4 GS Ge
Reason (N=15) (N=21) (N=16) (N=19) (N=15) (N=17) Total

Removing from packet_.--.--------- 4 6 5 2 5 4 26
Finding neck seal... 3 6 6 4 6 5 30
Spreading neck seal 4 5 7 5 7 6 34
Distending hood. 10 15 9 12 10 11 67
Pulling over head 2 4 6 6 6 5 29
Getting over hair__ 2 0 0 0 i 1 4
Getting over glasse: 1 2 2 4 0 2 11
Getting over nose, chin. 0 0 1 1 1 1 4

Total. 26 38 36 34 36 35 205

on over their glasses. Of the eleven bespectacled
subjects who did have some difficulty with this,
only two were in the briefing groups (G5 and
G6) which were given specific directions for
getting the hoods over their glasses. Although
analysis of this distribution did not reveal a
significant instructions effect, largely because
most subjects had no difficulty at all with their
glasses, the trend is in the direction which sug-
gests that giving subjects information about ways
to get the hoods over their glasses is helpful.
Since subjects were most likely to have prob-
lems getting their hoods fully inflated, they were
judged on how well they accomplished this in
donning the hoods. A subject. was judged to
have a fully inflated hood if the hood formed
an even cylinder from top to bottom around his
head. A rating of “minimally inflated” was
assigned whenever the hood touched the face or
side of the head. If the hood was not fully
distended (i.e., did not form a relatively smooth
cylinder) but was away from the head and face,
a rating of “partially inflated” was made. Table
2 presents the distribution of the ratings for
subjects in each group. It can be seen that 40%

‘Tape 2.-Oceurrences of Fully, Partially, and Minimally
Inflated Hoods, as Judged by Observers, Within Each
Briefing Group

Group
Degree of Inflation

Gl G2 G3 G4 G5 G6 Total

Fully inflated_ 3 6 9 12 4 8 42
Partially inflate - 8 tb 5 7 3 9 43,
Minimally inflated 4 4 2 0 8 1 18

27

of the subjects achieved fully distended, or
“perfect”, hood-donning, while 41% had “par-
tially inflated” and 18% had “minimally inflated”
hoods. It appears that groups G38, G4, and G6
were most successful with this aspect of donning.
Analysis of the distribution of judgments across
groups supported the conclusion that these groups
generally achieved more fully inflated hoods than
the others, Y?(5) =12.01, p<.05. Not unexpect-
edly, 54 of the 61 subjects given “partial” or
“minimum” ratings also had problems getting
the hoods distended before putting them on,
according to observers’ judgments.

Apparently, increasing the amount of infor-
mation presented in the briefings had little effect
on the time it took to don hoods, as can be seen
in Table 3.

Taspiy 3.—Mean and Range of Hood Donning Times
in Seconds for Each Briefing Group

Group

Gl G2 G3 G4 GS G6
Mean__._ 19.40 17.64 15.58 16.53 16.97 17.11
Range_-- 12-26 8-50 7-25 10-25.5 12-26 7-27

The nine subjects who donned their hoods
without problems took an average of 12 seconds,
while the remaining subjects took an average of
17 seconds. This difference was highly reliable,
116) =5.02, p<.001.

Affective Reaction to Hoods and Briefings.
Increasing the amount of information presented
about the hoods seemed to result in more positive


feelings about them, as can be seen in Table 4.
Analysis of the distribution of subjects having
no negative feelings versus those with negative
feelings across groups revealed a trend that ap-

TABLE 4.—Reactions of Subjects to Using the Safety
Hoods

Group

Response ——|§ —————--________
G1 G2 G3 G4* G5 G6* Total

7
31

No negative feelings__.

8 12 14 11 14 12
Had negative feelings... 7 :

9 2 7 1 6

*One subject did not respond.

proached significance including all six groups
(¥?(5) =10.45, p<.10), and achieved statistical
significance (Y*(4)=10.41, p<.05) when G6
(the only group to receive an increase in general
safety information in addition to hood informa-
tion) was excluded. Of the 31 subjects (304%)
who had some negative feelings about the hoods,
19 of them indicated they had some fear of a
shortage of air in the hoods, 11 felt reluctant. to
put a plastic bag over their heads, 7 said they
had some “panicky” feelings while wearing the
hoods, and 5 reported some feelings of claustro-
phobia (note that a subject could indicate more
than one kind of concern). It should be noted
that all of these 31 subjects, although expressing
some reservations about using the hoods, will-
ingly donned and wore the hoods. In fact, of
103 subjects, 98 replied that they would use the
hoods in an emergency, if requested to do so.
Generally (81.5%), subjects reported that they
did not feel that the briefings would be anxiety-
arousing prior to an actual flight. The 19 sub-
jects who did anticipate some increase in anxiety
were proportionally distributed across groups.
Thirteen of them were concerned by the pointing
out of potential emergencies, while six were un-
easy about the amount of material presented.
Retention of Safety Information. Overall, the
subjects were correct. on 73.4% of their responses
to the multiple choice questions assessing reten-
tion. The proportions of correct. test. answers
were approximately equal for all groups; there-
fore, the amount of information presented did
not seem to have much effect on retention.
There was no difference between the retention
rates for demonstrated and nondemonstrated
items. In fact, subjects in Groups G1 through

28

G5 did less well on the demonstrated than non-
demonstrated items.

There were marked differences among ques-
tions in terms of percentage of correct: answers.
The subjects did extremely well (correct 90%
or more of the time) when asked about the
location of the emergency exit information cards,
the use of the oxygen mask, the location of the
hoods, the procedures for inflating (G2 through
G6) and putting hoods on over glasses (G5 and
G6), and the types and use (for G6 only) of
water safety equipment. They did most poorly
on questions related to exits, and on how long to
wear the hood.

Effects of Previous Hood-Donning Experience

When the subjects in G6 were required to don
the hoods a second time, marked improvement
was noted. The mean donning time was reduced
significantly from 17.41 seconds for the first at-
tempt to 13.23 seconds for the second attempt,
#(16) =3.15, p<.01. Of the 17 subjects, 11 re-
duced their donning times by more than two
seconds, while only 2 subjects showed increases
of more than two seconds. Of these latter two
subjects, one had an initial donning time of nine
seconds which increased to twelve seconds on the
second trial. This represents a change from an
exceptionally fast time to a faster-than-average
time. The other subject was the only one in the
study with a signficant physical defect (a mal-
formed arm and hand), and her time on the
second trial was increased because she dropped
the hood. Even with the defect, it is noteworthy
that her first trial resulted in a very acceptable
donning time. Perhaps the most important
thing to note with respect to the effect of a
second trial upon donning time is that of the
six slowest subjects on the first trial (mean time
of 24.5 seconds), five of them reduced their times
by an average of 10.5 seconds.

The second trial also brought about a signifi-
cant reduction in the number of subjects who
encountered some problem in donning the hood
from 13 to 8, ¥?(1) =7.00, p<.01. Additionally,
the number of subjects who did not get their
hoods fully distended decreased from 10 on the
first trial to + on the second trial, again a signifi-
cant reduction, ¥?(1) =4.50, p<.05.

Sex Differences

Men and women did not differ in the time it
took to don hoods or the number of problems


 ——

Taste 9.—SEPTAL HOOD—FEMALE—ELEVATED TEMPERATURE—EXERCISING

SUBJECT #26 Surface Area: 1.658q.M ‘Temperature: 60°C Hood #000499
—— TIME—MINUTES
0 1 2 2,52
03 23 ©0654 6.0
20.9 17.8 11,2 10.8
— 86 104 114
— 24 23 26
SUBJECT #34 Age: 21 Surface Area: 1.63 Sq.M ‘Temperature: 60°C Hood #000489
—_ 0 1 2.00
03 2.36.0
_ 20.9 191 12.4
106 106 = 132
— uw
SUBJECT #35 Age: 21 Surface Arca: 1.74Sq.M ‘Temperature: 60°C Hood = #000523,
a 0 1 1,85 ~ ~
3.1 6.0
18.8 13.1
120158
32 42
SUBJECT #37 Age: 22 Surface Area: 1.73 Sq.M_ Temperature: 59°C Hood #000509
0 1 2 2,53
03 2.3 «5.8 6.0
20.9 19.6 13.8 11.8
102 140 144
— 8 20 28
SUBJECT #38 Age: 22 Surface Area: 1.438q.M ‘Temperature: 60°C Hood #000525
0 1 2 2.60
03 2.5 5.3 6.4
20.9 18.0 12,3 11.0
104 120 138 150
24 20 24 28

43




Taste 12.—-DRAWSTRING HOOD—MALE—NORMAL TEMPERATURE—EXERCISING

SUBJECT #9 Age: 22 Surface Area: 1,89 Sq. M Temperature: 26°C Hood #000282

TIME—MINUTES
0 1 2 3 4 5 6.00

3.1 4.4 4.4 4.7 4.7 4.7
18.7 16.7 16,2 15.5 14.8 14.7
104 121 122 125, 128 127

20 18 20 20 22 22
SUBJECT #12 Age: 22 Surface Area: 1.99 Sq. M Temperature: 26°C Hood #000327
0 1 2 3 4 5 6 6.43,

2.7 2.9 2.7 2.8 2.7 2.8 3.3,
18.5 17.5 17.5 17.8 17.6 17.6 17.5
124 122 122 124 123 125 120

20 19 16 i4 18 16 15
SUBJECT #27 Age: 21 Surface Area: 2,01 Sq. M Temperature: 27°C Hood #000380
0 1 2 3 4 5 6.05
1.2 1.8 2.2 3.0 2.4 2.4
19.8 18.5 18.0 17.3 17.3 17.5
79 87 89 93. 95 94
15 16 17 19 21 19
SUBJECT #30 Age: 19 Surface Area: 1.91 Sq. M Temperature: 27°C Hood #000239
0 1 2 3 4 5 6 6.18

2.6 4.1 5.2 5.9 5.9 5.9 5.9
17.8 15.6 14,2 14.0 14.2 14,2 14,2

82 96 104 106 106 110 112
15 16 18 20 19 22 24
SUBJECT #31 Age: 28 Surface Area: 1.83 Sq. M Temperature: 27° C Hood #000361
0 1 2 3 4 5 6.30

1.9 3.2 3.5 3.5 3.2 3.2
18.0 16.7 16.2 16.2 17.1 17.1
80 90 94 96 92 96
25 24 26 27 23 29

46


APPENDIX B

Part 3. Observer Rating Sheets

Subject name . Group I, II, III, IV, V, VI
Subject number Age Sex M. _F
Education Physical Disabilities
Glasses Yes _.______ No

1. Attention level during briefing.

(a) Attentive at all times.

(b) Attentive most of the time.

(c) Attentive about half of the time.
(d) Attentive for only a short time.
(e) Attentive at no time.

2, Time to put on hood from command

3. Observed difficulties in donning the hood.

(a) Removing from packet.

(b) Finding neck seal.

(c) Spreading neck seal.

(d) Filling with air.

(e) Pulling over head.

(£) Getting over hair.

(g) Getting over glasses.

(h) Getting over nose, mouth, or chin.

(i) Other (explain).

4. Adjustments of hood after donning.

(a) Neck seal.
(b) Re-positioned hood.

(c) Tried to further inflate hood.
(ad) Other (explain).

5. Final fit of hood.

(2) Hood on, fully inflated.

(b) Hood on, partially inflated.
(c) Hood on, minimally inflated.
(d) Poor seal.

(e) Not able to put on.

(f) Other (explain).

6. Observer’s comments.

55




APPENDIX A

‘Tapia 1—Description of Subjects

Subject Age Sex Height (Inches) Weight (Lbs.) Hair Length
1 25 M 69 170 Short.
2 25 F 67 135 Short
3 19 M 70.5 165 Short
4 27 M 69 160 Short
5 25 F 63.5 118 Short
6 27 M 70.5 145, Short
7 24 M 71.5 150 Short
8 25 F 66 140 Short
9 22 M 71 155 Short

10 27 F 66 125 Short
ul 24 F 63.5 128 Short
12 22 M 7 175 Short
13 22 F 69 123 Short
14 40 F 65.5 169 Short.
15 28 M 69 150 Short
16 28 F 68.5 138 Short
V7 20 M 70 160 Short
18 25 M 74.5 185 Short
19 21 F 55 100 Long
20 27 F 64 110 Short.
21 22 M 72 145 Short.
22 21 M 70 172 Short
23 22 M 74 175 Short
24 22 M 73.5 190 Short
25 21 M 68.5 160 Short
26 22 F 63.5 135 Long
27 21 M 72 175 Short
28 23 F ' 64 108 Short
29 7 F 63.5 120 Long
30 19 M 72 155 Short
31 28 M 68 155 Short
32 22 M 66 150 Short
33 25 M 70 220 Short
34 21 F 66.5 120 Short
35 21 F 68 137 Pony Tail
36 22 ¥ 65 115 Short
37 22 F 68 134 Short
38 22 F 62 100 Short
39 2 F 61 105 Long
40 26 F 63.5 15 Long

35


extent as to virtually eliminate visual cues for
evacuation.

After completion of the tests, each subject was
given a questionnaire in a self-addressed envelope
to be filled out and mailed to the principal
investigator.

These evacuation tests were designed to meas-
ure the flow of a maximum number of passengers

Tape 1.—Percentage of Subjects Choosing Each
Response Alternative to Items in a Post-Evacuation
Smoke Hood Questionnaire

Test Percent: Responding
Group —-————_———
Question Yes No Maybe None
1. Feeling of real A* 50.0 40.6 9.4 0
emergency BY* 35.9 50.0 14.1 0
2. Would have acted A 57.8 39.0 1.6 1.6
differently in actual B 60.9 26.6 9.4 3.1
accident
3a. Felt panic. _______ A 2.4 70.3 6.3 0
B 21.9 71.9 6.2*** 0
3b. Observed panic A 18.7 70.3 9.4 1.6
in others B 51.6 45.3 0 3.1
4a. Stewardess’s A 98.4 16 0 0
instructions clear Bs 98.4. «1.6 OO 0
4b. Heard instructions A 98.4. 1.60 0)
B 984 16 0 0
5. Expected more A 12.5 87.5 0 0
instructions B 15.6 844 0 0
6. Heard passengers A 32.8 67.2 0 0
give commands and B 23.4 76.6 0 0
assist others
7. Much confusion A 29.7 68.7. 1.6 0
was apparent B 48.4 51.6 0 0
8. Level of illumination A 84.4 10.9 04,7
was adequate for B 84.4 15.60 0)
evacuation
9. Hood waseasyto A 96.9 0 3.1 0)
put on B 98.4 16 0 0
10. Could see well A 90.6 94 0 0)
through hood B 87.5 12.5 0 0
11. Hood affected A 25.0 75.0 0 0
breathing B 14.0 84.4 O 1.6
12, Felt hood pro- A 96.9 3.1 0) 0
tected from smoke B 95.3 4.7 0 0
inhalation
None Slight Consid- Com-
erable plete
13. Degree vision A 21.9 34.4 35.9 7.8
obscured by smoke B 4.7 7.8 42.2 43.7
Before Smoke Heavy No
Smoke Start- Cabin Answer
ed Smoke
14. Hood donning A 39.0 59.4 1.6 0
Bo 42.2 53.1 0.0 4,7

*Includes subjects in Tests Al and A2
**Includes subjects in Tests B1, B2 and Cl
***During smoke only

33

oe

through only one exit and were not designed to
measure evacuation of an aircraft as an entity
through one-half or other prescribed number of
exits available. Total times cannot be directly
compared to requirements for such tests or dem-
onstrations.

II. Results and Discussion.

The findings from the evacuations are por-
trayed graphically in Figure 2. It can be seen
that the presence of smoke was the primary
variable influencing speed of evacuation, as both
evacuations with smoke were much slower than
those undertaken without smoke. The use of
hoods alone did not seem to have a significant
effect on evacuation rate, as can be seen by com-
parison of the curve for C1 with those of Al
and B2.

The poor performance during the B1 test rela-
tive to the A2 test (both with smoke and hoods),
was caused, at least in part, by a young child
whose hood drawstring became entangled in a
seat near the exit (this could not occur with the
newer type hoods). While the child was being
freed, the remaining subjects in the cabin (about
two-thirds of the subjects in that evacuation)
were prevented from making progress toward
the exit. None of those passengers who remained
for extended periods in the fuselage suffered any
apparent adverse effects due to carbon dioxide
accumulation or oxygen depletion.

Responses to the questionnaires are summarized
in Table 1. Significant differences in response
tendencies between groups were noted for the
second part of Question 3, Question 7, and Ques-
tion 13. The summation of these trends indicated
that more subjects appeared to panic, there was
more confusion, and there was greater reported
difficulty with vision in the B group than the A
group. Apparently, the experience gained with-
out smoke had a beneficial effect when subjects
were asked to evacuate under smoke conditions.

Elaborations of the questions were frequent,
and generally indicated that some subjects did
not care for the rebreathing of the warm air
within the hood; however, only one subject re-
ported any experience of increased breathing
rate. It should be noted that although several
subjects had minor complaints about wearing the
hoods, none of them became uncomfortable
enough to actually remove their hoods while in
smoke.


(1) How do you think you would feel prior to your first flight?

|

Extremely Moderately Some anticipation Moderately Completely
tense and tense and and excitement at ease at ease
uneasy uneasy but no fear and relaxed and relaxed
(2) Do you plan to fly in the future? Yes No
(3) Why haven’t you flown up to now?

(a) No opportunity.
(b) Fear of flying.
(c) High cost of air travel.

(d) Other. (Please explain below.)

3. How many exit doors were there in the aircraft?
(a) 8
(b) 6
(c) 4
(d) 10
4. Where were they located?

(a) Two in forward cabin, two in aft cabin, and four over wings.
(b) Two in forward cabin, two in aft cabin, and two over wings.
(c) Two in forward cabin, two in aft cabin.

(d) Two in forward cabin, two in aft cabin, two in galley, and 4 over wings.
5. How many doors were equipped with slides?

(a) Two in forward cabin, two in aft cabin.

(b) Two in forward cabin, two in aft cabin, two in galley.

(c) Two in forward cabin.

(d) Two in aft cabin.

6. Further information on using emergency doors was availabe (G1 thru G5 only)
(a) At the doors.

(b) From the stewardess.

(c) On the information card in the seat pocket.
7. To use door mounted slides (G6 only)

(a) Just open the door and the slide will fall into place ready for use.
(b) Pull the red handle to inflate the slide, then open the door.
(c) Open the door then pull the red handle to inflate the slide.

8. To use window exits (G6 only)

(a) Grasp the window, top and bottom, then throw it out in front of you.

(b) Pull the cover open on the top, pull the red handle inward and down, and holding the bot-
tom of the window, lift it in and set aside.

58


ee

Tani 2.—Estimation of Carbon Dioxide Production and Oxygen Consumption at Normal Temperatures assuming an
Initial Hood Volume of 20 Liters and No Leakage of the Septal Hoods.

‘Temperature Time
SUBJECT — (° Centigrade) CO» co/min. Op ce/min. (Minutes)

Male 1 26 277 436 4.18

Resting 3 26 271 410 4,20

4 26 301 186 4.32

6 25. 300 481 4,20

7 25. 244 316 4,50

Averages 279 366 4,28
Female

Resting 2 %6 235 303 4,43

5 25. 219 349 4,47

28 27 248 273 4,83

39 26 167 214 8.50

29 27 354 431 3.22

Averages 245 314 5.09

Male 9 26 553 793 2.42

Exercising 12 26 609 866 2.10

7 27 636 1000 2,42

30 7 808 1001 2.08

31 27 706 870 2.55

Averages 662 906 2.31

Female 13 25 509 784 2.63

Exercising ul 26 389 485 2,52

10 26 502 1163 2,63

8 26 417 403 2,83

36 27 634 678 2,08

Averages 490 703 2.54

jects were approaching their maximal work
capacity.

Female subjects exhibited lower rates of ac-
cumulation of carbon dioxide and consumption
of oxygen (Figure 3 and Appendix B, Tables
2-17). This may be attributed in part to their
smaller body size and surface area, but correc-
tions of these data for variations in surface area
did not entirely eliminate the difference; this
finding is consistent with other reports that
women, perhaps due to hormonal differences,
possess a lower metabolic rate per unit of body
surface.

As leakage from the septal hood was minimal
and assuming that a uniform hood volume of
20 liters is acquired at the time of donning, an
estimate of the rate of oxygen consumption and
carbon dioxide production during the test may
be derived (see Tables 2 and 3). A typical
oxygen consumption curve is presented in Figure
4,

An examination of the measurements of pen-
tane leakage (see Figures 5 and 6, as well as
Tables 4 and 5) reveals a clear superiority of the
Type S (septal) hood with respect to this vari-
able. Carbon dioxide and oxygen concentrations
were always consistent with hood pentane values:
when sudden increases in pentane concentrations
were noted, a commensurate rise in oxygen and
fall in carbon dioxide occurred. This was es-
pecially apparent in tests of Type D hoods;
sudden losses in seal integrity usually followed
obvious increases in depth of respiration, This
observation seems a clear demonstration of the
susceptibility of the non-rigid material to be
“pumped” by respiratory movements, a phenom-
enon which magnifies small imperfections in the
seal. In only one test did significant leakage of
Type S oceur within two minutes of initial ex-
posure, the female subject being one of those
who possessed hair long enough to extend below
the seal. Five other female subjects with equally


Taste 11.—DRAWSTRING HOOD—FEMALE—NORMAL TEMPERATURE—RESTING

SUBJECT #29 Age: 17 Surface Area: 1.57 Sq. M Temperature: 27°C Hood #000329

TIME—MINUTES
0 1 2 3 4 5 6 6.25

-03 la 2.3 3.0 3.0 3.0 3.0 3.0
20.9 20.1 18.3. 17.5 17.7 17.4 17.7 17.7

80 78 80 76 78 76 76 80
22 20 21 20 19 24 24 24

SUBJECT #28 Age: 23 Surface Area: 1.51 Sq. M Temperature: 27°C Hood #000282
0 1 2 3 4 5 6 6.43

1.0 1.8 L8 1.8 1.8 1.8 1.8
20.1 19.3 19.3 19.3 19.2 19.3 19.3

8 «82s7HC“<«é‘ SC‘ OOO CO
15 16 16 17 17 18 20
SUBJECT #5 Age: 25 Surface Area: 1.568q.M ‘Temperature: 25.5° © Hood #000327
: 0 1 2 3 4 5 6 6.43

1.6 2.5 2.5 2.4 3.1 2.5 1.9
19.8 18.9 18.6 18.5 18,2 18.5 18,4

91 87 85 83. 81 81 81
20 22 19 21 20 22 24
SUBJECT #2 Age: 25 Surface Area: 1.71 Sq. M Temperature: 26°C Hood #000239
0 1 2 3 4 4.50

1.5 25 2.6 2.6 2.6
19.6 18.8 18.8 18.7 18.7

7 95 84 81 84
26 26 21 18 26
SUBJECT #39 Age: 21 Surface Area: 1,44 Sq. M Temperature: 26° C Hood #000282
0 1 2 3 4 5 6 7 8 9 10. 50

03) 1.2 2.3 3.7 4.4 4.4 4.7 5.1 5.0 5.3 5.3
20.9 19.9 182 16.7 15.5 15.0 14.8 14.5 145 14.5 14,2
74 72 70 88 70 72 74 78 78 74 74
20 12 16 15 18 18 17 20 18 19 19

45


a

Taste 17—_DRAWSTRING HOOD—FEMALE—ELEVATED TEMPERATURE—EXERCISING

SUBJECT #26 __..-.----- Age: 22 Surface Area: 1.65 Sq. M Temperature: 60°C Hood #000329
TIME—MINUTES
0 1 2 3 4 5 6 6.20
-03 1.7 3.8 3.6 4,4 4.4 7.6 4.4
20.9 18.4 16.7 16.3 15.8 15.1 14,1 15.0
— 94 106 114 116 126 —— 1382
—_ 23 21 24 23 27 28 30
SUBJECT #34_____..-.-_- Age: 21 Surface Area: 1.63 Sq. M Temperature: 60°C Hood #000247
0 1 2 3 4 5 6 6.33
2.2 2.2 2.2 2.6 2.7 3.0 2.9
19.2 18,2 17.8 18.0 18.0 17.9 17.8
116 128 142 142 150 148 156
16 16 17 22 21 22 26

SUBJECT #35 Age: 21 Surface Area: 1.74 Sq. M Temperature: 60°C Hood #000360
0 1 2 3 4 5 6 6.12
3.0 O1 0.3 0.1 3.0 1.0 3.0
18.2 18.4 18.1 18.4 17.8 17.7 17.7
144 158 166 170 178 184
40 40 44 42 45 48

SUBJECT #37 Age: 22 Surface Area: 1.73 Sq. M Temperature: 60°C Hood #000360
0 1 2 3 4 5 6 6.22
2.9 3.4 3.7 4.1 4,2 4.3 4.3
18.4 16.8 16.6 16.6 16.4 16.4 16.4
134 146 160 164 172 172 168
19 19 25 26 29 29 40

SUBJECT #38 Age: 22 Surface Area: 1.43 Sq. M Temperature: 60°C Hood #000247
0 1 2 3 4 4.40
03 24 3.7 4.4 4.4 44
20.9 19.4 16,4 14.9 14.4 14.2
112 134 150 158, 160 160
30 24 23. 25 28 31

51


HOOD ON
y DELAY

PERCENT OXYGEN

I MINUTE

HOOD OFF

:

2 MiNUTES—>
MINIMUM

Fiaure 4. Representative recording of female subject exercising at 26° C, (Subject number 10). Delay is imposed
by gas stream time factors and slow response time of paramagnetic oxygen analyzers.

each subject in tests of both hood types. This
required that the effect of training be considered;
a subject already experienced in the donning of
one type, as well as in the experimental proce-
dures, might be more proficient in the use of a
second type and bias the comparison in favor of
the latter. To counterbalance this possibility,
preliminary tests with trained subjects were
undertaken. These forecast the results of later
experiments with naive subjects: a clear supe-
riority of Type S hood. Therefore, later experi-
ments were so organized that Type D was always
tested after Type S so that the elects of training
could be conferred on the inferior type; as the
results indicate, the effect (if any) of training
was of no apparent advantage to Type D.
Other preliminary experiments had demon-
strated another convenience of testing Type S
before Type D. As the latter leaked as much as
80% of exposure concentrations, the subject.
often inhaled a considerable amount of pentane
over several minutes, including the time elapsing
between removal of the hood and purging of the

test chamber. Predictably, this exposure allowed
a considerable amount of the fat-soluble pentane
to accumulate in the subject’s body so that, with-
out a long rest period between tests, the subject
would “give up” detectable amounts of pentane
to the atmosphere of the second hood, presenting
a false indication of leakage. With limitations
on the time which subjects could devote to the
test, relegating the hood more likely to leak to
the second test provided a more economic use of
subject time. Of course, when leakage did occur
during the first test, an appropriate “wash-out”
time was allowed before the next exposure.

The high solubility of pentane in the human
hody necessitated another consideration of data
obtained from hoods demonstrating slight leak-
age. In these tests there is some possibility of
false low readings, in that small amounts of
pentane passing slowly into the hood could be
absorbed by the subject at levels below the limits
of the hydrogen flame detector. Such error
would more likely obtain early in the exposure
period, since absorption by the body would de-


TABLE OF CONTENTS
Chapter

List of Contributors
Introduction

Section I. Environmental Protection

1. Evaluation of Leakage in Protective Smoke Hoods (J. M. McKenzie,
Ph.D., E. B. McFadden, M.S., J. M. Simpson, and P. R. Fowler,
MS.)

. Smoke Hood Effectiveness in a Toxic
den, M.S. and H. L. Gibbons, M.D.) ----------------------------

Lo

Section II. Sensory Effects

3. Vision Through Smoke Hoods (M. F. Lewis, Ph.D.) —-
4. Smoke Hood Tests: Acoustic Attenuation (J. V. Tobias, Ph.D.) ---

Section III. Operational Considerations

ot

. Effects of Variations in Safety Briefings Upon Use of Protective
Smoke Hoods (R. C. Smith, Ph.D.) ~----------------------------

6. Evacuation Testing Using Dense Theatrical Smoke (E. B.
den, M.S.)

References ____---------------------------------------------------

Appendix A. Evaluation of Leakage in Smoke-Flame Protective

Table 1. Description of Subjects
Table 2-17. Physiological Effects of Smoke Hoods -----

Appendix B. Safety Hood Briefings Study: Briefings, Rating Sheets,
and Questionnaires. ~----------------
Part 1. Briefings for Groups 1 through
Part 2. Briefings for Group 6
Part 3. Observer Rating Sheets -
Part 4. Briefing Questionnaire, I
Part 5. Briefing Questionnaire, II _

BD.
35.

36

oe
TARE D


he wore glasses, and whether or not he had any
significant physical defects.

Once the preliminary data had been obtained,
the subjects were instructed by the experimenter
concerning the experimental procedure. They
were told that they would hear a tape recording
of a briefing which would be similar to those
used aboard commercial airliners while a “stew-
ardess” (a college-age female selected and trained
in stewardess behavior) would demonstrate the
safety devices described in the briefing.

At the conclusion of the instructions, the ex-
perimenter started the tape recording of the
briefing appropriate for each group. There were
six groups in all, representing six variations in
the recorded briefings (see Appendix B, Parts 1
and 2 for all briefings). Group 1 (G1; N=10M,
5F) heard the least elaborate briefing which
consisted of a greeting, statement of emergency
exit locations, description of use of the oxygen.
mask, and a statement of the location and pur-
pose of the safety hood. During this, and all
other, brefings the “stewardess” pointed out the
exit locations, demonstrated the use of the oxygen
mask, and demonstrated the donning of the
safety hoods. Each subsequent briefing, with a
different group of subjects present, increased the
amount of informaton given about the donning
of the smoke hood, although the stewardess gave
the same demonstration during all briefings.
Group 2 (G2; N=12M, 9F) heard the same
briefing as G1 except that subjects in G2 were
also told how to remove the hood from its packet
and how to spread the neck seal while putting
it on. Group 3 (G8; N=11M, 5F) was told to
shake the hood out to fill it with air, in addition
to the other information supplied to them.
G cup 4 (G4; N=12M, 7F) was told to pull the
hood down over their heads as they would a
shower cap, while Group 5 (G5; N=11M, 4F)
was told, instead, about how to clear their glasses
when donning the hoods. Group 6 (G6; N=12M,
5F) was given the most. elaborate donning in-
structions, as well as more elaborate descriptions
of emergency exit procedures and water Janding
safety devices (which were not. demonstrated).
At the conclusion of each briefing, the subjects
were told that, on the experimenter’s signal, they
were to put on the smoke hoods which were
located on the backs of the seats directly in front
of them, as quickly and as well as they could.
At the signal, the subjects put on their hoods

26

and the observers determined the length of time
it took for each hood-donning. ‘The subjects
remained seated during the entire hood-donning
exercise.

After the completion of the hood-donning all
subjects were given a questionnaire appropriate
to the briefing which they had heard. The first
questionnaire was the same for all groups (see
Appendix B, Part 4) and dealt primarily with
the smoke hood and the subject’s reaction to it.
Subjects were asked if they had difficulty putting
on the hood, if they had negative feelings about
the hood, and if they felt they would use it in
an emergency. The second questionnaire (see
Appendix B, Part 5) included questions about
the subject’s attitude towards safety briefings in
general, and assessed their retention of the ma-
terial presented to them in the briefing.

Group 6, in addition to completing the tasks
described above, also donned the hood a second
time. For the second donning, the experimenter
reviewed the procedure for donning the hood
with them after they had completed their ques-
tionnaires. They were then supplied with new
hoods and were told again to put on their hoods
when signalled by the experimenter. As before,
the observers timed and rated each subject's
performance.

III. Results.
Briefing Effectiveness

Hood-Donning Efficiency. Nearly all subjects
(95.2%) felt that the instructions presented to
them were clear with respect to the use of pro-
tective hoods. Most subjects were less than per-
fectly efficient, however, in donning the hood.
According to the observers’ ratings, 90.3% of
the subjects encountered some sort of problem
in donning the hoods, although all were able to
get the hood on satisfactorily and quickly. As
can be seen in Table 1, no group seemed to have
more problems than any other group (note that
column totals may exceed N in any group, since
a subject could be rated as having more than one
kind of problem). Subjects seemed to have the
greatest difficulty in competely inflating the hood
(so that it woud contain a maximum amount of
air), although they also seemed to have some
problems with finding and spreading the elastic
neck seal. Seventeen of twenty-eight bespec-
tacled subjects had no problems getting the hoods


During their exposure within the chamber,
subjects were able to traverse linear distance
ranging from 108 to 220 feet and performed
from 11 to 25 double switching operations.

Tapte 1—Blood Carbon Monoxide Saturation Prior to
and Following Exposure of Subjects Wearing Smoke
Hoods in a Smoke Chamber

Percent Carbon Monoxide
Saturation

IV. Discussion and Conclusions.

Since the variations in the blood carbon mon-
oxide saturation obtained in this study were of a
magnitude which is not significant, it must be
concluded that the smoke hood provided the
subjects with adequate protection from the
respiratory effects of 2 toxic environment. Fur-
thermore, it was shown that even with hoods on,
subjects were able to travel linear distances which
would usually exceed those required in the move-
ment to emergency exits in aircraft. It is also
notable that these hooded subjects were able to

these conditions.

Subject Sex Hemoglobin Pre-exposure Post-exposure perform a relatively large number of discrete
1 M = 16.4¢m.% 0.00 0.00 switching operations under
2 Fo 14.0 gm. % 2.46 4.98 Since effective evacuation requires manipulation
3 M  16.8gm.% 0.00 0.00 .. y *
of exits, etc., as well as movement to exit areas,
4 F 14.0 gm. % 0,00 0.00 ae . ; .
5 M 17.4em.% 3.96 3.96 the ability of subjects to perform these operations
6 M 17.4gm.% 5.96 1.98 in a toxic environment while wearing hoods was
7 F 15.2gm.% 0.00 0.00 tested and confirmed.
TIME AND SWITCHING DISPLAY PANEL
DOOR / {SWITCHING STATIONS 1-8
Xa
=F
| 3
a
=
a
ir
4
4

= >

Haiste >) [

7 5
aa
6
a 16! >|
Ficury 1. Diagram of smoke chamber, Arrows indicate maze pathway.

18



Qualified requesters may obtain Aviation Medical Reports from Defense Documentation
Center. The general public may purchase from Clearinghouse for Federal Scientific and
‘Technical Information, U.S. Dept. of Commerce, Springfield, Va. 22151.


TABLE 4.—SEPTAL HOOD—MALE—NORMAL TEMPERATURE—EXERCISING

SUBJECT #9

Age: 22 Surface Area: 1.89 Sq. M Temperature: 26°C Hood #000525
TIME—MINUTES
0 1 2 2.42
3.3 5.8 6.7
18.5 13.1 11.3
104 119 126
20 19 26

SUBJECT #12 Age: 22 Surface Area: 1.99 Sq. M Temperature: 26°C Hood #000489
0 1 2 2.10
3.8 6.4 6.4
17.8 12.3 11.8
128 129 120
21 19 20

SUBJECT #27 Age: 21 Surface Area: 2.01 Sq. M Temperature: 27°C Hood #000506
0 1 2 2,42
2.2 7.5 U7
18.3 11.3 8.8
81 91 96
18 20 33

SUBJECT #30 Age: 19 Surface Area: 1.91 Sq. M ‘Temperature: 27°C Hood #000493
0 1 2.08
-08 49 84
20.9 16.3 10.5
88 80 98
4 14 15
SUBJECT #31 Age: 28 Surface Area: 1.83Sq.M Temperature: 27°C Hood #000499
0 1 2 2.85
08 32 69 9.0
20.9 16. 11.6 9.8
86 82 88 88
12 22 24 30

38


each. (The Standard calls for six trials for each
of ten subjects.) The tests were made in the
CAME anechoic chamber, with a Grason-Stadler
Model E800 Békésy Audiometer, a MeIntosh
MC-240 power amplifier, and a Heath AS4IU
loudspeaker and baflle assembly.

Each subject was tested twice—once with and
once without the hood over his head. Whether
the first trial was with or without the hood was
randomly determined. In the tests with the hood,
each subject put it on in the test chamber (after
instructions) and took it off for a moment half-
way through the test, in order to prevent an
uncomfortable accumulation of carbon dioxide.
A subject had the hood on for two periods of
one minute, forty seconds during that trial.

‘The listener was provided with a microswiteh
to depress when he could hear the test tone, and

to release when he could not. The switch con-
trolled the recording attenuator of the Békésy
Audiometer, automatically increasing and de-
creasing intensity of the pure-tone signal while
simultaneously graphing the setting of the at-
tenuator. During this procedure, the frequency
of the signal was changed at a constant rate to
cover the range from 100 to 10,000 Hz. From
this continuous spectrum, nine frequencies were
selected for analysis: 125, 250, 500, 1000, 2000,
3000, 4000, 6000 and 8000 Hz.

IH. Results and Conclusion.

As shown in Figure 1, the CAMI smoke hood
does not interfere with the transmission of sound
waves. At most, the threshold shift is 83 dB at
5000 Hz, an amount that is barely discriminable.



Chapter 6.

Ernest B. McFadden, M.S.

I. Introduction.

It was the purpose of this investigation to
determine the reactions of a naive group of sub-
jects to the use of the protective smoke hoods
during evacuations in the presence of smoke.

II. Method.

Subjects were obtained from the University
of Oklahoma Research Institute under contract.
A majority of the subjects were obtained through
the use of newspaper advertisements. Generally,
the individuals were from lower economic groups
and unfamiliar with air travel.

Specifications of age and sex of the subjects
were as follows:

Ten percent were to be over age 60.

Eight to ten percent were to be under age 12.

The remainder were to be within the 12-60
age bracket.

Thirty percent were specified to be females.

All subjects were paid for their participation
in the experiment.

Sixty-four seats were installed in an obsolete
Constellation L-749 fuselage, per the attached
drawing. Minimal or less than minimal aisle
widths were incorporated in the seating plan
(Figure 1).

Exits available in this aircraft consist of the
overwing exits, small crew door, and the main
cabin door at the left aft portion of the fuselage.
In order to assure longer duration exposures in
the environment. only the aft main cabin door
was utilized.

Motion picture cameras were used to record
behavior during evacuations. One camera was
located inside the cabin and two were positioned
outside the cabin. All tests were carried out
under outdoor daylight conditions.

Evacuation Testing Using Dense Theatrical Smoke

FWD

31¥,"

3" [sfso] **" (s9]3s
35° [as 3] 18% Tote
30 [63

SLIDE

_[s4[s3] 3) 28[57

. 59 [4a] 45)" 52/48

=| 1c
_[ 31 [47[46]'*4[ 1 [20

_ PNESEGI- ESE .

2 2 |23] "sa [2

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. 3a [ee] er]? 6 [17

a0[41 [33] '74/ 10 [29

se] i2[6a]'*4[60[38|

Freure 1.

of the test aircraft.

AFT

to location of subjects in tests Al and A2.

31

Seat spacing and aisle width configuration
Numbers in seat blocks refer


Chapter 3. Vision Through Smoke Hoods
Mark F. Lewis, Ph.D.

I. Problem.

Although the optical transmission of the
Schjeldahl smoke hoods has been determined by
rophotometric measurement*, it remained
ssary to determine the effects of the smoke
hood on the vision of human observers. The
current. study examines the optical transmission
of the hood by visual photometry and examines
the hood’s etfect on visual acuity

Il. Method.

In the determination of optical transmissions,
two samples of smoke hood materials were used,
one without aluminization (from Type 8 hoods),
the other aluminized with a clear band (from
Type D hoods), From the first sample, three
test patches were used, From the second sample,
four test patches were used. Determinations of
optical transmission were made by measuring the
change in luminance produced by interposing
the test patches between the light source (spectra
100-foot-Lambert reference source) and the
measuring instrument (Macbeth ilwminometer).

The tests of visual acuity were designed to
represent a worst-case situation. Accordingly,
subjects were adapted to an illumination in ex-
cess of that provided by normal aireraft interior
lighting. This “normal” illumination was set at
30-foot-candes, measured at seat level down the
center line of the laboratory. This exceeds the
15- to 25-foot-candles provided by aircraft read-
ing lights and the 5- to 15-foot-candles general
illumination at aircraft armrest height. Emer-
gency illumination was simulated by adjusting
the voltage to a tungsten lamp to provide 0.05-
foot-candle illumination at the target. In accord
with industry procedures, illuminations were
sured with a Photo Researeh Corporation
‘andela foot-candle meter.

Nine male and three female adults with vary-
ing basal acuity were used as subjects. Those

19

subjects whose acuity was less than normal wore
either corrective spectacles or contact. lenses.
The test procedure was as follows: With normal
illunination on, the subject was seated 10 feet
from the test target and adapted to normal
illumination for one minute. Basal acuity was
measured using a standard Bausch and Lomb
test chart (Snellen Rating; illiterate-direct read-
ing, number 713598-102ND). Following meas-
urement of basal acuity, the subjects were
instructed to wait for the lights to go out and
then to read each test card as quickly as possible.
Subjects were instructed that they were to guess
about the items on each test even if they were
unsure of their responses. Prior to tests with
hoods, subjects were shown how to don the hoods
and how to look through them. Following one-
minute adaptation to general illumination, the
lights were turned out. Test runs began 10
seconds after the lights went out and each rum
was complete within one minute. Following
completion of each run, the lights were imme-
diately turned on and another one-minute pre-
adaptation period began. Each run consisted of
serial presentation of targets from the Bausch
and Lomb test chart. These were individually
mounted on white stock and corresponded to
decimal acuities of 0.25, 0.33, 0.40, 0.50, 0.67,
0.80, 1.00, and 1.33. Targets were presented in
ascending order of difficulty in each run,

Eight runs were made for each subject, four
in the no-hood condition and four with hoods,
For half the subjects, hood tests preceded no-
hood tests, This condition was reversed for the
other half of the subjects. For hood tests, the
subjects were instructed to put the hoods on as
soon as the lights went out, and to remove the
hoods as soon as the lights came back on. ‘They
were told to look through the non-aluminized
portion of the hood. With each subject. two
hoods were used and were alternated on successive



increase in the tidal volume or depth of breath-
ing usually seen with elevated concentrations of
carbon dioxide (Figure 2).

Analysis of the records of gas concentration
indicated that uniform mixing of the gases
within the hood was not usually obtained until
hyperventilation developed: thus, earlier carbon
dioxide values were more variable than similar
measurements obtained toward the end of the
experiment (Figure 2). The hood, being made
of a pliable material, acts as 2 mixing pump

RESPIRATION

CARBON DIOXIDE

when respiratory movements are great enough
to operate it.

Termination of the experiment was ordered
by an observer who accompanied the subject
within the chamber. Discontinuation of the test,
therefore, did not always indicate that the sub-
ject had attained maximum voluntary tolerance.
The most marked difference between the septal
and drawstring hoods was the observation that

3%
ONE MINUTE ae

TIME (SECONDS)

HOOD ON PENTANE

ALUM AU

NAM ANAMY AA f i nt |

Two minutes 5%

APA Age,
poi dea hes

pon

| 2.63 MINUTES
6.6%

TIME (SECONDS)

Ficure 2. Representative continuous recording of female subject exercising at 26° C.

HOOD OFF
(Subject number 10).


for your added protection in the event of an
emergency. They are to be used in the event of
an emergency evacuation, or upon direction of a
crew member. The stewardess will now demon-
strate their use. To remove the hood from its
package, pull up on either red tab. Open the
hood to its maximum size by spreading the neck
seal with your hands and shaking it out as the

53

— ee

stewardess is now doing to fill it with air. Then
quickly pull the hood down over your head. For
those of you wearing glasses you may find it
easier to put the hood on the back of your head
first, then pull the opening of the seal forward,
stretching it to clear your glasses as the stew-
ardess is now demonstrating. Remove the hood
after you are safely away from the aircraft.


OO

TABLE 5.—SEPTAL HOOD—FEMALE—NORMAL TEMPERATURE—EXERCISING

SUBJECT #13 Age: 22 Surface Arca: 1.69Sq. M ‘Temperature: 25°C Hood #000513
ae —_ TIME—MINUTES :
0 1 2
28 54
17.3 11.8
99 102
19 17
SUBJECT #11 Age: 24 Surface Area: 1.61Sq.M ‘Temperature: 26°C Hood #000509
0 1 2
0867 Bl
20.9 20.3 17.8
124188125
20 17 ~~ 20
SUBJECT #10 Age: 27 Surface Area: 1.64Sq.M ‘Temperature: 26°C Hood 4000493
0 ~ 1 2
08 2.049
20.9 17.2 12.1
8292105
ee 19
SUBJECT #8 Age: 25 Surface Area: 1.73 Sq.M Temperature: 26°C Hood #000527
0 1 2
3 48
19.5 16.8
115 124
1 8
SUBJECT #36 Age: 22 Surface Area: 1.568q.M_ ‘Temperature: 27°C Hood #000489
0 1 2
.03 3.5 6.6
20.9 16.5 13.8
94 = 108120
1 2 20



a

TasLe 7—SEPTAL HOOD—FEMALE—ELEVATED TEMPERATURE—RESTING

SUBJECT #20 Age: 27 Surface Area: 1.52 Sq. M Temperature: 60°C Hood #000509
TIME—MINUTES
0 1 2 3 4 5 5.82
+03 21 2.8 3.8 4.6 6.7 7.9
20.9 19.6 18.4 16.9 15.1 12.8 12.3
92 86 82 80 84 100 102
16 13 ul 13 14 16 16
SUBJECT #19_----------- Age: 21 Surface Area: 1.32 Sq. M ‘Temperature: 58°C Hood #000525
0 1 2 3 4 5 5.25
1.6 2.4 4.6 6.0 7.4 74
20.5 19.3 17.1 15.2 13.6 13.5
HR...----------2-------- 102 106 102 100 106 108 112
Resp__------------------- — — — — — —
SUBJECT #16 Age: 28 Surface Area: 1.76 Sq. M Temperature: 59°C Hood #000515
0 1 2 3 4 5 6.05
21 3.7 5.0 6.2 71 7.9
19.3 17.3 15.5 13.1 10.7 9.3
104 74 80 80 90 86
15 12 14 13 14 18
SUBJECT #14 Age: 40 Surface Area: 1.84 Sq. M Temperature: 57°C Hood #000506
0 1 2 3 3,25
03 1.9 1.9 5.5 6.3
20.9 20.7 20.38 «17.0 15.8
— 83 87 89 102
—_— — 4 17 19 24
SUBJECT #40 Age: 26 Surface Area: 1.54 Sq. M Temperature: 60°C Hood #000515
0 1 2 3 4 5 6 7 7.31
2.3 24 4.0 5.0 4.9 6.0 8.6 8.7
19.5 18.8 16.9 15.3 15,0 140 41.5 11.0
78 78 80 82 84 92 102 104
13 13 15 15 16 17 19 20

41


Tape 3.—Estimation of Carbon Dioxide Production and Oxygen Consumption at Elevated Temperatures Assuming an
Initial Volume of Twenty Liters and No Leakage of the Septal Hoods.

Temperature Time
SUBJECT — (Centigrade) CO» ce/min. 2 co/min. (Minutes)

Male 17 58 —_—* 393 5.45
Resting 15 56 364 328 3.90
18 56. —-* 449 5.08

32 59. 422 429 3.08

33 87 435 645 3.13

Averages 407 449 4.12
Female 20 60 271 296 5.82
Resting 19 58 282 282 5.25
16 59 261 383 6.05

4 57 388 316 3.25

40 60 238 271 7.31

Averages 288 310 5. 54

Male 21 59 694 1107 2,42
Exercising 22 60 664 978 2.50
23 62 676 1081 2,22

24 60 676 1126 2.13

25 60 —_* 1027 3.00

Averages 677 1064 2.45
Female 26 60 476 801 2.52
Exercising 34 60 600 851 2.00
35 60 650 843 1,85

37 59 AT4 719 2.53

38 60 492 846 2.60

Averages 538 812 2,30

*COz concentration exceeded calibration.

long hair did not experience, during the first two
minutes, significantly greater leakage than those
with short hair. No male subjects with long
hair were employed in these tests, as multiple
use was intended, but it is possible that the male
hair styles of this type could allow a somewhat
greater leakage than was observed in this study.
Observations made during the tests indicate that
in long-haired subjects who did not experience
leakage the hair lay quite flat and seemed to
completely fill the space between neck and seal,
whereas in the one subject who experienced leak-
age, the long strands became grossly separated
to either side of the neck, providing a gap.

The results obtained from tests of the Type D
(drawstring) hoods show considerably greater
variability than those from Type S experiments,
with an overall leakage far greater than Type S.
The variability over the exposure period with

Type D is probably due, in part, to variations
in donning. Observers noted that some subjects
did not draw the seal as tight as did other sub-
jects; there was also some tendency for the draw-
string to stick or foul. The particular draw-
string used in these hoods was permanently
attached at one end. This allows it to be drawn
tight with one hand, but this refinement may
have been confusing to some subjects who ap-
peared to be searching for two ends as they
tightened the seal. Type S hoods probably
yielded more uniform results because less skill
is required for efficient use and less variation in
donning is allowed by the design; the Type S
tended to be more fully inflated due to trapping
of air by the seal as the device was pulled over
the head.

Because of the limits on the number of naive
subjects available, it was necessary to employ