A system for producing a stream of humidified sterilizing gas for sterilizing objects such as the water systems of space vehicles and the like includes a source of sterilant gas which is fed to a mixing chamber which has inlet and outlet ports. The level of the water only partially fills the mixing chamber so as to provide an empty space adjacent the top of the chamber. A heater is provided for heating the water in the chamber so as to produce a humidified atmosphere. The sterilant gas is fed through an arcuate shaped tubular member connected to the inlet port of the mixing chamber for producing a vortex type of flow of sterilant gas into the chamber for humidification. A tubular member extends from the mixing chamber for supplying the humidified sterilant gas to the object for being sterilized. Scrubbers are provided for removing the sterilant gas after use

Bryan, C. J.

Moyers, C. V.

Wright, E. E., Jr.

English

NASA Technical Reports Server

United States Patent [I91 
Bryan et al. 
[111 4,250,143 
[45] Feb. 10, 1981 
[S4] SYSTEM FOR STERILIZING OBJECTS 
FOREIGN PATENT DOCUMENTS 
[7S] Inventors: Coleman J. Bryan, Merritt Island; 594002 3/1960 Canada ...................................... 422/34 
1077246 7/1967 United Kingdom ...................... 422/34 Edward E. Wright, Jr., Titusville; 
Clyde V. Moyers, Cape Canaveral, all 
of Fla. OTHER PUBLICATIONS 
“Bennett Centrifugal Air Washer”, Wilcox-Bennett 
Carburetor Co., Minneapolis, Minn. 1731 Assignee: The United States of America as remesented bv the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
Primary Examiner-William F. Smith 
Assistant Examiner-Chris Konkol 
[21] Appl. NO.: 46.739 
[22] Filed: Jun. 8, 1979 
[SI ]  
[52] 
[S8] 
Int. C1.I .......................... A61L 2/08; A61L 9/00; 
G05D 23/00 
U S .  C1. ........................................ 422/109, 422/3; 
422/27; 422/30; 422/34; 261/79 A 
Field of Search ............... 422/109, 1 1  1 ,  120, 123, 
119 R, 130, 153, DIG. 65 
422/125, 26, 27, 28-30, 34, 3 ,  306; 261/79 A, 
[561 References Cited 
U.S. PATENT DOCUMENTS 
968.456 
1213.887 
2,235,998 
2.756.976 
2.759.713 
3.392.034 
3.767.362 
3.854.468 
3,954,406 
8/1910 
1/1917 
3/1941 
7/1956 
8/1956 
7/ I968 
IO/ I973 
I2/ I974 
5 /  1976 
Edwards ............................ 261/79 A 
.................. 261/79 A 
Barnes .................................... 422/27 
Griffin et at. 422/27 
Nozaki ............................... 261/79 A 
Chamberlain .......................... 422/27 
Attorney, Agent, or Firm-James 10. Harrell; John R. 
Manning 
1571 ABSTRACT 
A system for producing a stream of humidified steriliz- 
ing gas for sterilizing objects such as the water systems 
of space vehicles and the like. The system includes a 
source of sterilant gas which is fed to a mixing chamber 
having inlet and outlet ports. Water is carried in the 
mixing chamber with the level of the water only par- 
tially filling said mixing chamber so as to provide an 
empty space adjacent the top of the chamber. A heater 
is provided for heating the water in said chamber pro- 
ducing a humidified atm,osphere. The sterilant gas is fed 
through an arcuate shaped tubular member connected 
to the inlet port of the mixing chamber for producing a 
vortex type of flow of sterilant gas into the chamber for 
being humidified. A tubular member extends from the 
mixing chamber for supplying the humidified sterilant 
gas to the object for being sterilized. Scrubbers are 
provided for removing the sterilant gas after use. 
3 Claims, 2 Drawing Figures 
L 
https://ntrs.nasa.gov/search.jsp?R=19810016189 2020-03-21T09:51:40+00:00Z
U.S. Patent Feb. 10, 1981 4,250,143 
4,250,143 
1 2 
SYSTEM FOR STERILIZING OBJECTS 
ORIGIN OF THE INVENTION 
The invention described herein was made by employ- 
ees of the United States Government and may be manu- 
fdctured and used by or for the Government for govern- 
mental purposes without the payment of any royalties 
thereon or therefor 
BACKGROUND OF THE INVENTION 
Heretofore, ethylene oxide has been utilized as a 
FteriliLing ga5 mixture and has been primarily used in a 
batch type process using a variety of sterilizing auto- 
clave\ into which the object or objects to be sterilized 
&ire placed. Moi4ture in the form of steam or water is 
then introduced in the evacuated autoclave followed by 
pressurization of the autoclave with the dry ethylene 
oxide gas mixtures. These processes all rely on gas mix- 
ing and diffusing to ensure uniform humidification of 
the sterilant. 
One problem with utilizing autoclaves is that you do 
not always obtain uniform mixing of the gases. Another 
problem with utilizing autoclaves is that it is not readily 
adapted t o  be used for sterilizing a lot of different ob- 
jects at different times. Another problem is that be- 
tween each test, the pressure of the autoclave has to be 
reduced and the steam mixture of ethylene oxide and 
water has to be evacuated. Between each sterilization, 
the water carried in the bottom of the autoclave must be 
reheated to generate the steam for mixing with a new 
supply of ethylene oxide mixture. 
To be an effective sterilant, ethylene oxide gas should 
be humidified to between 40% to 80% relative humidity 
throughout the system to be sterilized. Because of the 
many dead end cavities, tanks and long runs of small 
diameter tubing existing in an integrated system, contin- 
uous humidification of the ethylene oxide/Freon 12 
mixture is necessary as the evacuated system is filled 
and pressurized to 20 to 22 p h the sterilant. This 
ensures that all areas of the are contacted with 
humidified sterilant. 
Examples of apparatus and methods of controlling 
the relative humidity of gaseous sterilizers and steriliz- 
ing equipment are disclosed in United States Pat. Nos. 
3,687,612, 3,791,424, 3,761,362, 3,620,265, 3,897,210 and 
3.85 1.043 
SUMMARY OF THE .INVENTION 
The invention includes a system which can be readily 
used for sterilizing relatively inaccessible objects such 
as water tanks and water lines with a continuous supply 
of a pressurized sterilizing gas mixture. The system 
would be particularly adaptable for sterilizing the water 
systems and tubes leading to the water systems of space 
vehicles such as a space shuttle prior to use or reuse. It 
could also be readily used in municipalities for steriliza- 
tion of water systems and in hospitals, clinics, biological 
testing laboratories, and other environments ' which 
require sterilization. 
The system includes a source of sterilizing gas mix- 
ture such as 12% ethylene oxide/88% Freon-12 that is 
carried within a pressurized container. The pressurized 
gas mixture is fed through a heated coil for ensuring 
that the mixture is converted from a liquid state to a 
gaseous state. A mixing chamber is provided having a 
heater positioned adjacent the bottom thereof and a 
water level which only partially fills the chamber so as 
5 
10 
15 
20 
2 5  
30 
35 
40 
45 
50 
55 
60 
65 
to provide an empty space adjacent the top of the cham- 
ber. The gas mixture is fed into the mixing chamber 
through an arcuate tubular member so as to produce a 
vortex type of flow within the empty space of the cham- 
ber. While in the chamber, the gas mixture is humidified 
to between 40% and 80% relative humidity. Connected 
to the output of the mixing chamber is a tubular member 
that can be readily connected to the object to be steril- 
ized such as the water system in a space shuttle. A re- 
turn tubular member is also connected to the object 
being sterilized and fed through a plurality of scrubbers 
which remove the ethylene oxide prior to venting to the 
atmosphere. 
Accordingly, it is an important object of the present 
invention to provide a system for producing a gaseous 
mixture of ethylene oxide and water according to a 
predetermined percentage so as to be an effective steril- 
ant. 
Another important object of the present invention is 
to provide a system for producing a gas mixture of 
ethylene oxide which is humidified to a relative humid- 
ity of approximately 40% to 80% producing a continu- 
ous supply of sterilizing gas for sterilizing objects that 
are relatively inaccessible. 
Another important object of the present invention is 
to provide a system for sterilizing objects which cannot 
be readily placed within containers such as sterilizing 
autoclaves. 
Still another important object of the present inven- 
tion is to provide a system for producing a sterilizing 
gas mixture of a predetermined relative humidity that 
can be readily controlled. 
These and other objects and advantages of the inven- 
tion will become apparent upon reference to the follow- 
ing specification, attendant claims and drawing. 
BRIEF DESCRIPTION OF THE DRAWING 
FIG. 1 is a flow diagram illustrating a system for 
producing a continuous flow of sterilizing gas con- 
structed in accordance with the present invention; 
FIG. 2 is a sectioiial view taken along line 2-2 of 
FIG. 1 illustrating an arcuate member for conveying the 
gaseous mixture within a mixing chamber. 
DESCRIPTION OF T H E  PREFERRED 
EMBODIMENT 
Referring in more detail to FIG. 1 of the drawing, 
there is illustrated a commercial tank 10 of ethylene 
oxide and freon having a ratio of 12% ethylene oxide 
and 88% Freon-12. Normally, the mixture is in a liquid 
state maintained under pressure. Connected to the tank 
10 is a valve 12 which controls the flow of the liquid 
from the pressurized tank 10. The pressurized liquid 
flows through a tube 14 into a heater water bath 16. The 
heated water bath 16 includes a coil of tubing 17 that is 
directly connected to the tube 14. Water is carried 
within the bath 16 and a heater 19 is provided for heat- 
ing the water to a predetermined temperature to ensure 
that the liquid entering the coiled tubular member 17 is 
converted to a gaseous state. Connected to an exit end 
of the coil tube 17 is a pressure regulator 18 which is 
adjustable for regulating the pressure of the gas flowing 
through tubes 20 and 22 extending from the water bath 
to a flow temperature meter 24. The flow temperature 
meter 24 measures the rate of flow of the sterilant gas 
therethrough as well as the temperature of the gas. 
3’  
4,2;50,T43 
A mixing chamber 26 is provided for receiving the 
gas mixture from the flow temperature meter 24 and 
includes a hot plate 28 upon which a vessel 30 is carried. 
A top 32 is provided on the vessel 30 and has an inlet 
port 34 provided therein as well as an exit port 36. 
Connected to the inlet port 34 is an arcuate shaped 
member 38 which extends down into an empty space 
provided between the top of the water level 40 and the 
top 32 of the vessel. The arcuate shaped tubular member 
38 produces a vortex type of flow around the vessel so 
as to provide efficient mixing of the ethylene oxide/- 
Freon gas with water vapor provided in the empty 
space. 
The temperature of the heater or hot plate 28 can be 
varied for controlling the percent of humidification of 
the ethylene oxide/Freon mixture. A temperature con- 
trol and instrumentation circuit 42 is provided for con- 
trolling and sensing the now and temperature of the gas 
flowing through the meter 24, the temperature of the 
water 40 carried within the vessel 30, and the humidity 
and temperature of the humidified gaseous mixture 
entering the object being sterilized. As illustrated sche- 
matically in FIG. 1, the object being sterilized is a water 
tank 44 provided in a space shuttle 46. A temperature 
and humidity sensor 48 is interposed in a line SO leading 
to the water tank. The line 50 is, in turn, directly con- 
nected to the outlet port 36 of the mixing chamber. 
The sensing probe 48 sends a signal back to the tem- 
perature control and instrumentation circuit 42 so that 
the system can be adjusted for maintaining the desired 
amount of humidity in the gaseous mixture. 
The gaseous mixture, after sterilizing the water sys- 
tem 44 of the space shuttle 46, is fed into a scrubber by 
means of tube M. The scrubber includes three vessels, 
Mu, 566, and 56c. Each of these vessels include a perfo- 
rated coil tube 58 and is filled with a solution of 1/10 
molar sulphuric acid. As the sterilizing mixture is bub- 
bled through the solution carried in the scrubber, it is 
absorbed therein. In order to ensure that all of the gase- 
ous mixture is absorbed, the vessels 560 through 56c are 
connected in series so that the output of vessel !Xu is 
connected to the coil member 58 of vessel 561, and the 
output of the vessel 566 is, in turn, connected to the coil 
tubular member 58 of vessel 56c. In each of these ves- 
sels, the gaseous mixture is bubbled through the solution 
prior to exiting that particular vessel. The output of 
vessel 56 c is vented to the atmosphere through a vent 
60. 
A pressure regulator 62 is interposed in the tubular 
member 50 extending between the mixing chamber 26 
and the object being sterilized so as to regulate and 
maintain the proper pressure of the sterilizing gas dur- 
ing the sterilizing process. As a result of the mixing 
chamber producing a continuous stream of sterilizing 
gas, the tubular member SO can be readily connected to 
any object that is desired to be sterilized such as water 
pipes, vessels, water systems, etc. 
In FIG. 2, the arcuate shaped tubular member 38 is 
illustrated showing the direction that the sterilant gas 
takes when entering the mixing chamber. As a result of 
4 
the liquid gas assuming a vortex type of flow around the 
empty space of the mixing chamber, the degree of hu- 
midification of the gas it is mixing can be readily con- 
trolled. 
While a preferred embodiment of the invention has 
been described using specific terms, such description is 
for illustrative purposes only, and it is to be understrood 
that changes and variations may be made without de- 
parting from the spirit or scope of the following claims. 
1. A system for producing a humidified sterilizing gas 
(a) means for supplying a pressurized sterilant gas; 
(b) a mixing chamber having a closed top and bottom; 
(c) inlet and outlet ports provided in said top of said 
S 
10 What is claimed is: 
mixture for sterilizing an object comprising: 
I5 
mixing chamber; 
(d) water carried in said mixing chamber with the 
level of said water only partially filling said mixing 
chamber so as to provide an empty space adjacent 
the top of the chamber; 
(e) a hot plate heating said water in said chamber to a 
predetermined temperature producing a humidi- 
fied atmosphere in said empty space; 
(9 means for feeding said sterilant gas through said 
(g) an arcuate shaped elongated tube connected to 
said inlet port and extending into said empty space 
of said chamber for producing a vortex type of 
flow of sterilant gas in said chamkr  through said 
humidified atmosphere so as to be humidified; 
(h) tubular means connected to said outlet port for 
conveying said humidified sterilant gas tQ said ob- 
ject for sterilizing said object, 
(i) a temperature and humidity sensor carried in said 
tubular means connected to said outlet port; 
(i) temperature and humidity control means con- 
nected to said temperature and humidity sensor, 
said mixing chamber, and said hot plate for main- 
taining said humidified sterilizing gas at a predeter- 
mined degree of relative humidity. 
2. The system as set forth in claim 1 further compris- 
said means for supplying sterilant gas including: 
’O 
” inlet port; 
3o 
Js 
40 
ing: 
45 (i) a pressurized tank of ethylene oxide/Freon 12 in 
(ii) a heater, 
(iii) tubular means supplying said ethylene oxide/- 
Freon 12 from said tank to said heater for con- 
so verting said ethylene oxide/Freon 12 from a 
liquid state to a gaseous state. 
3. The system as set forth in claim 1 further Compris- 
a plurality of scrubbers connected to said object 
being sterilized for receiving exhaust gases from 
said object; and 
a gas absorbing solution carried in said scrubbers for 
removing said sterilant gas from said humidified 
gas mixture. 
a liquid state, 
ing: 
55 
* * * * *  60 
65 


System for sterilizing objects

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