Armored Force 
Medical. Research Laboratory 
Fort Knox, Kentucky 
PROJECT NO. 3 - TOXIC GASES IN ARMORED VEHICLES 
Final Report On 
Sub-Project No, 3“15 - Determination of the Characteristics and 
Effects Upon tiie Crew of Gun Fumes from 
Firing of the Weapons in the M4A4E1 Tank 
Project No. 3-15 
April 29, 1943 ARMORED FORCE MEDICAL RESEARCH LABORATORY 
Fort Knox, Kentucky 
Project NOo 3-15 
7U9o2-12 GNOML 
April 29, 19143 
1„ PROJECT: No. 3 - Toxic Gases in Armored Vehicles. Final Report 
on: Sub-Project No. 3-15, Determination of the Characteristics and Effects 
Upon the Crew of Gun Fumes from Firing of the Weapons in the Tanko 
a« Authority - Letter, Commanding General, Headquarters Armored 
Force, Fort Knox, Kentucky, U00.112/6 GNOHD, dated September 2k, 19h2, 
b0 Purpose - To determine the extent of the hazard from fumes re- 
leased by"*firing of the weapons in the MliAliEl tank with 103>mra howitzer. 
2. DISCUSSION: 
a. Methods and Conditions of Test. 
(1) Fire Pattern: 
(a) 105mm Howitzer: The piece vras fired at the rate of 
one (1) round every 10 seconds in bursts of 5° Three such bursts were fired 
at 5 minute intervals. Total, 15 rounds. 
(b) Machine Guns: The bow machine gun was not fired 
since the piece and mounting are the same as in other tanks of the Mlj series, 
previously reported (See Report on Sub-project 3-1, 3-5, February l£, 19U3). 
Three belts of 100 rounds each were fired from the turret machine gun in a 
total of 8 minutes. Each belt was expended in approximately two minutes0 
(2) Ammunition: 105 mm; ammunition 50-50, shell Ml; machine 
gun, caliber o30 ball. 
(3) Tank Operation: Tank buttoned-up and motor running at 
normal idling speecL Full crew in -tank. Wind, 6 mph quartering lf>0°. 
(U) Analysis; Air samples were analyzed for carbon monoxide 
and ammonia; bloods taken from the crew members before and after firing were 
analyzed for carbon monoxide hemoglobin. Details of the analytical procedures 
may be found in the report on Sub-projects No. 3-1, 3-5, February 15, 19U3<» 
Results of the present test are presented in the Appendix. 
3, CONCLUSIONS: 
a• Howitzer: 
(I) Of the crew, the loader is exposed to the highest carbon 
monoxide concentration The blood of the loader showed an increase 
of carbon monoxide hemoglobin during the firing of 15 rounds0 (2) The other turret crew members encounter lower concentrations 
of carbon monoxide, while exposure of the men in the bow is negligible* 
(3) Irritation of the eyes and nose was experienced by the 
loader with ammonia concentrations of 16£ and 290 ppm. 
(U) There was no accumulation of carbon monoxide or fumes 
from one burst to another« 
($) Under the conditions of these tests atmospheric conditions 
in the turret were not satisfactory 0 The efficiency of the crew was impaired 
by the ammonia and other irritating fumes and a definite hazard from*carbon 
monoxide was presento More effective turret ventilation is neededo 
bo Turret Machine Gun: 
(1) The average concentration of carbon monoxide exceeded 
0*2% at all turret crew positions during the firing of the turret machine gun0 
At the loader's position the concentration was above 0.3*. 
(2) Although the test lasted only 8 minutes (being terminated 
then because of danger to the crew) and only 300 rounds were fired, high 
concentrations of carbon monoxide were found in the blood of the turret crew 
members, the increase ranging from 11 to 1%% during the test* . 
(3) Ammonia and other fumes built up to such high levels in 
the turret during firing that the turret crew members were unable to execute 
their normal tasks effectively, 
(U) The serious problem presented by the turret machine gun 
results from the manner of mounting the gun with its muzzle some distance 
back of the mantlet. As a result, noxious gases escaping from the muzzle as 
well as from the breech are drawn into the turret. 
U. RECOMMENDATIONS; 
a. 105 ram Howitzer0 
(1) That independent exhaust ventilation be provided in the 
turret for the control of fumes from the 105mm howitzer, (See Report on Control 
of Gun Fumes in Mil Series Medium Tanks, Sub-Projects No, 3-1, 3-5, Eeb. 15, 19it3)„ 
(2) That the turret machine gun be mounted in such a manner as 
to prevent entry of fumes from the gun muzzle into the turret0 
Prepared by: 
Captain Norton Nelson, SnC 
Captain Steven M. Horvath, SnC 
Captain Ludwig Eichna, MC 
Lieutenant Robert Walpole, SnC 
APPROVED 
WILLARD MACHLE, 
Colonel, Medical Corps, 
Commanding. 
3 Incl. 
#1 - Appendix 1 
#2 - Tables 1, 2, & 3 
#3 - Fig. 1, v 2 APPENDIX 1 
Results 
lo 105mm Howitzer: 
The problem of gun fumes from the howitzer is of the same 
order of magnitude as from the 75mm gun in the standard MiiAli tank, in spite 
of the fact that a greater quantity of toxic gas is produced by the larger 
piece (Table 1 and Fig. 1). Offsetting the higher CO production is an 
increased air movement through the turret resulting from the less tightly 
fitting gun mount0 Evidence of better ventilation is seen in the more rapid 
clearance rate in the MiiAliElj 12 seconds (Table 1) as compared with 50 seconds 
in standard MliAli. 
The greater work entailed in loading the heavier ammunition makes the 
situation of the loader somewhat more serious in the case of the subject tank 
than when operating the 75mm piece. The increased lung ventilation resulting 
from the higher work rate leads to more rapid accumulation of carbon monoxide 
in the bloodo Thus, in a 15 minute exposure the CO hemoglobin increased to 
Hi. (Table 3) whereas in the standard MliAli the blood concentration was only 
22% after 30 minute exposure to approximately the same atmospheric concentra- 
tion of COo 
2. Turret Machine Gun: 
Conditions were so severe during firing of the turret machine gun that 
the trial was stopped after only 300 rounds had been fired* It is estimated 
from the blood concentrations of carbon monoxide (Table 3) that had the standard 
test (1000 rds) been completed serious carbon monoxide poisoning, and possibly 
unconsciousness, would have resulted. The high blood carbon monoxide content 
reflects the extreme atmospheric concentrations to which the crew were exposed 
(Table 2 and Figure 2) 
The highly hazardous situation presented by this weapon results from 
the trapping of muzzle fumes directly behind the mantlet and subsequent collection 
in the turret* The gun muzzle is practically within the turret; the barrel 
terminates some distance behind the mantlet and the turret opening through which 
it passes is large. Thus, a considerable portion of the muzzle fumes are drawn 
into the turret with the inflowing air. It is doubtful if the difficulty can 
be corrected by increased ventilation. The gun should be remounted so as to 
extend through the mantlet or a large enough opening provided in the shield 
to insure outward escape of the muzzle gases. 
Incl. //I TABLE 1 
CONCENTRATIONS OF CARBON MONOXIDE AND ANMONIA 
From Howitzer 
- 
Peak Concentrations at End of Burst 
Carbon Monoxide, 
Percent 
Ammonia, 
p.p.ra 
After 2nd Burst 
0.1*33 
290 
After 3rd Burst 
Oo277 
165 
Aver. Concentration by Cont. Sampling 
Loader 
0.110 
Commander 
0.06Ii 
Gunner 
0.037 
Clearance Rate after 2nd burst 
(Time for Cone* to decrease 5>0$) 
12 seconds 
TABLE 2 
CONCENTRATIONS OF CARBON MONOXIDE AND AMMONIA 
From Turret Machine Gun 
Peak Concentrations at End of Belt 
Carbon Monoxide, 
Ammonia, 
Percent 
p.p.m 
During 1st Belt 
0.ij66 
180 
During 3**d Belt 
0.376 
110 
Aver. Concentration by Cont, Sampling 
Loader 
0.336 
Commander 
0.2 Uh 
Gunner 
Oo2l8 
Tncl. f2 TABLE 3 
CARBON MONOXIDE CONCENTRATIONS 
IN BLOOD OF ORE?/ MEMBERS 
gEii;--; - 
CRM 
MEMBER 
CO Hemoglobin 
as % of Total Pigment 
Before 
Exposure 
After 
Exposure 
Increase 
10£ am Howitzer * 
Loader 
1.9 
16.5 
1U.6 
Commander 
1.1 
3.0 
1.9 
Gunner 
0.0 
5.0 
5.0 
Driver 
3.U 
U.o 
0.6 
Asst. Driver 
U.2 
JU.8 
0.6 
Turret 
Mo G• 
Loader 
0.2 
15.3 
15.1 
Commander 
0.9 
13.2 
12.3 
Gunner 
0o2 
11.6 
n.i* 
Driver 
— 
5o0 
** 
Asst. Driver 
** 
1.8 
— 
♦ 1$ Minute Exposure 
*-* 8 Minute Exposure Fig. I 
CARBON MONOXIDE CONCENTRATION 
FROM 105 MM HOWITZER 
Fig. 2 
CARBON MONOXIDE CONCENTRATION 
FROM THE TURRET MACHINE GUN 
LEGEND 
PEAK CONG. 
DIE AWAY CONG 
CONG. BY MS A 
AVG. CONG. 
RDS. FIRED 
.LOADER 
COMMANDER 
CARBON MONOXIDE PERCENT 
CARBON MONOXIDE PERCENT 
GUNNEK 
MINUTES 
MINUTES 
Fig. I 
Fig. 2 
ina. #3