Viewgraphs of increased fire and toxic contaminant detection responsivity by use of distributed, aspirating sensors for space station are presented. Objectives of the concept described are (1) to enhance fire and toxic contaminant detection responsivity in habitable regions of space station; (2) to reduce system weight and complexity through centralized detector/monitor systems; (3) to increase fire signature information from selected locations in a space station module; and (4) to reduce false alarms

Youngblood, Wallace W.

English

NASA Technical Reports Server

ECLSS TECHNOLOGYFOR SPACESTATIONEVOLUTION FIREANDTOXIC
TOPICS JANUARY 16".19,1990 GASDETECTION
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INCREASEDFIREAND TOXIC CONTAMINANT
DETECTIONRESPONSIVITYBY USE OF
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ECLSS TECHNOLOGYFOR SPACESTATIONEVOLUTION FIREANDTOXIC
TOPICS JANUARY16-19, 1990 GASDETECTION
AS Space Station Freedomevolves and matures over its lifetime, it is anticipated
that there will be a need to enhance its habitable region fire and toxic contaminant
responsivityand sensitivity,especially in those regionsof low air circulation rates•
Such regionsmay include unpoweredequipment racks, storage bins, etc. The use
of distributedsensors with centralizeddetectors is suggested as an efficient means
for accomplishing this goal. The use of the concept described herein for Space
Stationapplicationwas suggestedby Matt Cole of the NASAJohnsonSpaceCenter•
_, The concepthasbeen outlinedin Reference1I--L •
Go
The use of more sensitive detectors and, possibly, detection devices of different
types can produce enhanced fire signature information leading to reduced false
alarms. The conceptdescribedherein is notintendedto replace already plannedfire
detectiondevices, but is meantto supplementthemwith increasedinformation.
Reference1" Youngblood,W.W. andVedha-Nayagam,M.: AdvancedSpacecraftFireSafety:
ProposedProjectsand ProgramPlan. NASACR 185147,October 1989.
] l } I I I I I I ! I I I I i I
1 _ ) I 1 I 1 '1 1 I " )'l " I 1 ! 1 1 1 I s 1 1
ECLSS TECHNOLOGYFOR SPACESTATIONEVOLUTION FIREAND TOXIC
TOPICS JANUARY 16-19,1990 GAS.DETECTION
OBJECTIVES:
• ENHANCE FIRE AND TOXIC CONTAMINANT DETECTION RESPONSIVITY
IN HABITABLE REGIONS OF SPACESTATION
• REDUCESYSTEM WEIGHT AND COMPLEXITYTHROUGH CENTRALIZED
DETECTOR/MONITORSYSTEMS
• INCREASE FIRE SIGNATURE INFORMATION FROM SELECTED
LOCATIONSIN A SPACESTATIONMODULE
• REDUCEFALSEALARMS
ECLSS TECHNOLOGYFORSPACESTATIONEVOLUTION FIREANDTOXIC
TOPICS JANUARY16-19, 1990 GASDETECTION
The concept of fire detection by means of aspirating flow through long tubes is
commonly used in earth-based systems. Fenwal Inc. markets the VESDA (Very
Early Smoke DetectionApparatus)fire detectionsystem which draws air through a
long tube to a central detector for the early detection of incipient fires in such
critical areas as computer rooms (Reference 2). The Brunswick Corporation has
developedaspiratingflow tube sensors for mining activities such as underground
haulageways (Reference 3). Tube lengths in this case measure up to several
hundreds of meters. More recently, the Systron/Donner Co. has marketed anL'O
aspirating flow smoke detector for use in aircraft cargo bays. This system uses the
aircraft ventilation system to induce flow through ionization-type smoke detectors
from specificregionsof the cargobay (see accompanyingfigure).
Reference2: Johnson,P.F.: Fire DetectionIn ComputerFacilities. Fire Technology,Volume22,
No. 1, February1986,pp.14-32.
Reference3: Thomas,E.D.: A PneumaticSamplingFire DetectionSystemIn An Underground
Haulageway.IEEETransactions,IndustrialApplications,VolumeIA-19,No.3, Part1,
May-June1983,pp.440-444.
I , } I ] ] I I J t I I I 1 ! _ , I i
I _., I 1 1 I 1 ......I 1 1 1 ! 1 1 1 1 t '_ ! 1)
ECLSS TECHNOLOGYFOR SPACESTATIONEVOLUTION FIREAND TOXIC
TOPICS JANUARY 16-19,1990 GAS DETECTION
ASPIRATINGSMOKE DETECTORS: AIRCRAFT CARGO BAY
ASPIRATING
FLOW SMOKE
(3 TYP)
., ,( -----VENTILATION
z" SYSTEM AIR
RETURN DUCT
L=. !
/AIRCRAFT CARGO
BaY (PLAN VIEW)
ECLSS TECHNOLOGYFORSPACESTATION EVOLUTION FIREANDTOXIC
TOPICS JANUARY16-19, 1990 GASDETECTION
The schematicof the centralizeddetector/monitorconceptshows a numberof
distributedsensors (SL(1), SL(2)... SL(N)) feeding into a central detectorunit
via a programmableselection valve. The sensors consist of small diameter
tubes through which air from selected locations is induced to flow by means
of a fan unit and/orconnectionto a ventilationsystemair returnduct.
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bo
t_ The conceptdescribedherein is not intendedto replace fire detectiondevices
in powered equipment racks and other potentially hazardous regions. The
distributed sensor concept is designed to monitor quiescent regions of
spacecraft modules and provide enhanced monitoring of gaseous
contamination.
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I I I I l I "I .....I 1 .... 1 1 ! 1 I 1 "" 1 1 I .... 1
") ) )
ECLSS TECHNOLOGYFORSPACESTATIONEVOLUTION FIREAND TOXIC
TOPICS JANUARY 16-19, 1990 GASDETECTION
GENERAL SCHEMATICOF CENTRALIZED
DETECTOR/MONITORCONCEPT
SL(1) SL(2) SL(3) SL(4) SL(5) SL(6) SL(N)
,JimII,
SELECTION
VALVE
_o
I ]CENTRAL ALARM/CONTR.
DETECTOR _1 COMMAND I
UNIT _1- -- --I SYSTEM I
FAN UNIT
SL: SOURCELOCATIONS(1, 2, 3... N) .L
THC:TEMPERATURE& HUMIDITY
CONTROLSYSTEM MODULEAIR
RETURN
(THC)
ECLSS TECHNOLOGYFORSPACESTATIONEVOLUTION FIRE ANDTOXIC
TOPICS JANUARY 16-19,1990 GASDETECTION
The centralized detector/monitor can include one or more types of fire
detectorsand/orcontaminationmonitors. Typically,the ionization-typesmoke
detectorsare currentlyused in pressurizedregionsof spacecraftand aircraft.
The centralizeddetector/monitorconceptallows the additionof other detector
types, i.e., photo-extinctionsmoke detectors, and specific gas sensors sucht'o
"= as those sensitive to CO and CO 2. In addition, the use of the centr_dized
detector as a source for a mass spectrometer (MS) or gas chromatograph/
mass spectrometer(GC/MS)would provide additional fire signature informa-
tion. Further,the source locationof gaseous contamination(especiallytoxic
species)couldbe morecloselydetermined.
I _ _ I I I I l l I l I I 1 I I I , _ I I
I I ._ 1 1 "1 1 '1 'I I I '1 " I "l .... i 1 .... ] 'I , ] I) ,)
ECLSS TECHNOLOGYFOR SPACESTATIONEVOLUTION FIREAND TOXIC
TOPICS JANUARY16-19,1990 GASDETECTION
CANDIDATETYPESOF FIRE/GASEOUSCONTAMINATION
DETECTION DEVICESFOR CENTRALIZEDMONITORING:
• SMOKEDETECTORS
- IONIZATION
_" - PHOTO-EXTINCTION(LIGHTSCATTERING)
¢j1
- PARTICLE COUNTERS
• GASSENSORS
-- CO, CO2, 02, H2
- OTHER
• GC/MS
ECLSS TECHNOLOGYFOR SPACESTATIONEVOLUTION FIRE ANDTOXIC
TOPICS JANUARY 16-19,1990 GASDETECTION
The paper fire signature response,shown opposite (based on UL 217, Test A), is
representativeof a slowly pyrolyzing process followed by flaming combustionat
about240 secondsin the example. The resultsshown are from one of several tests
on various materials,all of whichwere intendedto illustratethe relative responseof
different types of fire detectors exposed to different fire scenarios (Reference 4).
Also, the test results lend supportto the premisethat fires may be detectedin their
early stages by solid state sensor detection of selected smoke gases. In all of the
tests related by Reference4, the standardtypes of fire detectiondevicestested (i.e.,
ionizationand light-scatteringsmoke detectors,UV sensors, and thermal response
sensors)lagged in responsebehindthe productionand detectionof rapid increasesO_
in CO and/orCO2 .
Note that the scale units for the ordinate of the figure shown opposite are as
follows: CO2 (200ppm/unit),CO (10ppm/unit),CxHy (12 ppm/unit), H2 (10 ppm/unit).
Reference4: Pfister, G.: Detectionof Smoke Gases By Solid State Sensors -- A Focus on
ResearchActivities. FireSafetyJournal,Volume6, No. 3., 1983,pp. 165-174.
I i I 'I ] I 'I .....1 I I I I I 1 "I I _ " 1 I
) ) /
ECLSS TECHNOLOGYFORSPACE STATION EVOLUTION FIRE AND TOXIC I
TOPICS JANUARY 16-19, 1990 GASDETECTIONI
PAPERFIRE - UL 217, TESTA (OUTBREAKOF FIREAT ~240SEC.)
i i
10 I '
_ I RF S
8- I co I co2
/ R- LIGHTSCATTERING
b_ - I _. CxHy
-4 SCALE ! F - IONIZATIONUNITS 8 - I
(SEE I co2
TEXT) 4- _ _" :'..... ";': II _ _0 S-RADIATIONt .." ". v .,
/ OOIOO I i_o I t 1 " I '1 I I I I ' I " I
0 30 60 90 120 150 180 210 240 270 300 330
TIME, SECONDS (REF.4)
ECLSS TECHNOLOGYFORSPACE STATION EVOLUTION I FIRE AND TOXIC
TOPICS JANUARY 16-19, 1990 I GASDETECTION
Standardcombustiontests are routinelyperformedon a wide varietyof materialsto
evaluate the lethality of the gases evolved from the process. The figure shown
opposite illustrates the production of CO, HCL and HF from a nonflaming
combustiontest of a specific wire insulationmaterial. The proprietaryresults were
obtained from a standard NIST test wherein the material was inserted into a
_ preheated oven at 25°C below autoignition temperature and maintained in that
oo environmentfor 30 minutes.
The resultsshownare not meantto imply that there are universaland unambiguous
fire signatures for all fire scenarios in terms of the gaseous species produced.
However,the detectedincrease in any of a numberof gases, i.e., CO, CO2, H2, HCL,
HF, HCN, etc., can be an independent indication of an unwanted or threatening
event. The indicated event could be a gaseous spill or leak, a severe thermal
degradation,a smolderingcombustion,etc.
I .. ,- t J I I ] 1 I I I I _ I .! ! , .... ] I
I " .) I I I I I I I 1 I l l 1 I I _ I I
ECLSS TECHNOLOGYFOR SPACESTATIONEVOLUTION FIREAND TOXIC
TOPICS JANUARY 16-19, 1990 GASDETECTION
NONFLAMING COMBUSTION OF A POLYMERIC WIRE INSULATION
3600 WIREINSULATION I 7200
NISTNONF1.AMINGTEST
3200 /r _-..,_ (25"C BELOWAUTOIGNmON) 6400/ \ I I
/ ",,. I I 5600
,_--CO
2800 / ,,,,)f,_ _% P_" ,/ _ ,2400 HCL ---" / - " _. _ __ 4-800
2000 _ 4000
HF, HCL I / _ .. COCONCEN-
CONCENTRATION I / _ _ TRATION (PPM)(PPM) 16oo I / "'----_______2oo
12ooI / 2400
/ "! _ 1600800 /
400 , _ _ 800
o /-I" 0
0 1 2 3 4 5 6 7 8 9 lO 11 12 13 14
TIME(MINUTES)
ECLSS TECHNOLOGYFORSPACESTATIONEVOLUTION FIREAND TOXIC
TOPICS JANUARY 16-19,1990 GASDETECTION
The accompanyingfigure illustratesthe conceptwherein multiple sensingtubes are
connected to one or more centralized detector/monitor units located in a Space
Station module. The sensing tubes may be made of small diameter (_ 0.64 -
0.95cm), light-weightmaterialscompatible with all spacecraftsafety requirements.
Air from the sensing locations is induced to flow to the central unit by meansof a
fan unit or, alternatively, by connecting the outlet of the unit to the low pressure
regionof the ECLSSair handlingreturnducting.
cJ1
co
Ideally, no more than one or two central detector/monitor units would be required
for each moduleto supplementthe other fire detectionand contaminantmonitoring
devices already planned for Freedom. The time required to sense all of the
distributed locations will be determined as a "trade-off" between what is desired
and what can be accomplishedgiven the transittimes for each sensingtube.
! ," 1 I ) I I 1 I ! I I i I I ! , , I !
! _ x I ' I ! 1 1 "1 1 1 1 "I 1 1 I " 1 ..... I , I 1J ) /
ECLSS TECHNOLOGYFOR SPACESTATION EVOLUTION FIRE ANDTOXIC
TOPICS JANUARY 16-19, 1990 GASDETECTION
CENTRALIZEDSMOKE DETECTORS/MONITORS:SPACE
STATIONAPPLICATION
CENTRALIZED SMOKE
DETECTOR (2-4, TYP)
c_
I
I
I
ZSPACE STATION MODULE
TUBES
FOR CONTAMINANT
SOURCES
ECLSS TECHNOLOGYFORSPACE STATIONEVOLUTION FIREAND TOXIC
TOPICS JANUARY 16-19,1990 GASDETECTION
A simplified schematic of a centralized detector/monitor is shown in the figure
opposite. Current ground-basedsystems of this concept typically utilize only the
smokedetectors-- usuallyof the ionizationor photo-extinction/light-scatteringtype.
The concept shown in the schematic is somewhat idealized since it assumes the
availability of small,solid-stategasdetectorssensitiveto CO and CO2.
The inclusion of a mass spectrometer(MS) or gas chromatograph(GC)/MS makes
ol
the centralized detector/monitor especially attractive. Most enclosed, habitablebO
spaceson earth do not have, or cannot afford the luxury of a GC/MS. Its inclusion
on SpaceStationFreedomgreatly enhancesthe use of "expert systems" to interpret
and communicatethe existance of an incipientfire or some other event producing
off-nominalaerosolsand/orgaseouscontaminants.
I J ] 1 ) I ] f I I ) ) / I ) I i _ ] I
l '1 1 1 ] 1 ] ..... ' \ ] ]I '_, I 1 ! 1 " l 1 '1
j_
/ J
ECLSS TECHNOLOGYFOR SPACE STATION EVOLUTION FIRE AND TOXIC
TOPICS JANUARY 16-19, 1990 GAS DETECTION
CANDIDATEDETECTORSFORINCLUSIONIN CENTRALIZEDMONITOR
ASPIRATINGAIR FLOW FROM
SELECTED SOURCELOCATIONS
I J
I I
i[-'1--- 1'-
.... --4 -7
_' _J LJ
I
I
i
DETECTORS: _ )"
• GASEOUS _,. I ALARM/CONTR.
- CO2, CO ),,. I SYSTEM
- MS,GC/MS ._>. L..
° SMOKE
- IONIZATION(ION.)
- PHOTO-EXTINCTION(PE)
VIEWA-A
ECLSS TECHNOLOGYFOR SPACESTATIONEVOLUTION F-_-AND TOXICJTOPICS JANUARY16-19, 1990 _. G S ETECTION
¢J1
co
(This page left intentionally blank.)
ECLSS TECHNOLOGYFOR SPACESTATION EVOLUTION FIREAND TOXIC I
TOPICS JANUARY 16-19,1990 " GASDETECTIONI
"O SOMEPRACTICAL CONCERNSRELEVANTTO USEOF
m
DISTRIBUTEDSENSINGTUBES:
Z
"o
._ • RESPONSE (TRANSIT) TIMES MUST BE REASONABLYQ
m SHORT
:z • EXIT SIGNATURES MUST CLOSELY .MATCH SENSING
o REGION CONDITIONS
-.I
"rl
r'-
o • SENSING TUBES MUST NOT INTERFERE WITH OTHER
SYSTEMS OR OPERATIONS
ECLSS TECHNOLOGYFORSPACESTATIONEVOLUTION FIREAND TOXIC
TOPICS JANUARY 16-19, 1990 GASDETECTION
Someeffort has already been expendedto determine the transit times for smoke
ladenair through small diametertubing (e.g., Reference5). The inducedflow may
be either turbulentor laminar dependingon the tube diameterand mass flow rate
through the tube. For very large pressure drops, the flow may correspond to
compressibleconditions ratherthan incompressibleas normallyassumedfor air
at low velocitiesand low pressuredrops (i.e., < 100 torr_ P).
c_o
c_ The accompanying figure illustrates some approximate transit times based on
relationshipsderived in Reference5. For spacecraft applications, it is suggested
that transittimesof ~ 5-7secondsmay be appropriate.
Reference5. Hertzberg,M. andLitton,C.D.: MultipointDetectionof Productsof CombustionWith
TubeBundles.BuMinesReportRI 8171,USDI, September1976.
l I I I I I I I I 1 I I I "I I I _ ' "I I
ii
I ECLSS TECHNOLOGY FOR SPACE STATION EVOLUTION I F|RE AND TOX|C
TOP|CS JANUARY 1_E19_i 1990 GAS DETEC_T|ON
TYPICAL TRANSITTIMES FORAIR THROUGH
SMALL DIAMETERTUBING
13
12
15 torr (8 in. H=0)11
FLOW:AIR @ 20°C
10 INLET PRESSURE:745 tort
9
co
"_ 8
F TRANSll]ON:TURBULANTTO lAMINAR7TRANSITTIME,
(sec.) 6 L = 33.8m
5
= 0.43cm
4 I
0.63cm
= 20m
2
1 I L= 10m rll
0
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
PRESSUREDROP. A P (tort)
ECLSS TECHNOLOGYFOR SPACESTATIONEVOLUTION FIREANDTOXIC
TOPICS JANUARY16-19,1990 GASDETECTION
During the transmission of smoke laden air through very long (> 100 m) unheated
tubes, some agglomeration and wall condensation will occur with the result that
a large percentage of the smallest, submicrometer smoke particles may be "lost."
This is especiallyimportantto sensingtube systemsused in undergroundmines
and haulagewayswhere the tube length may be several hundred meters. This
transmissionloss is illustratedby the accompanyingfigure taken from Reference
(_ 5 for a tube ID of 0.43 cm.
oo The short tube lengthsanticipatedfor a spacecraftsuch as Freedomshould pose
no significantparticle loss problem. However,experimentaldeterminationmust
be undertaken to evaluate both transit times and particle losses for practical
spacecrafttubelengths,tube diameters,flow rates, type of smoke,etc.
I J _) 1 ) I 1 I 1 I I I 1 I I ! ! i 1 I
1 I 1 1 1 1 I I 1 1 1 I I 1 I 1 _ ' 'I 1
) J ,'
ECLSS TECHNOLOGYFOR SPACESTATIONEVOLUTION FIREANDTOXIC -I
TOPICS JANUARY 16-19,1990 GASDETECTIONI
MEASUREDAND PREDICTEDSUBMICROMETER
PARTICULATETRANSMISSIONS
I.O
_400A
o.s
\
\\
\
_O.I \ TUBE DIAMETER,
0.43 cmhi
\
KEY
• Agedwoodsmol_ \
o Cool smoke /
Mecsured \
---_Predicted for variousparticle diameters
\I00 A
Turbulent Lominot -----
.oJ I ,,,I I I I :
O 50 IOO 150 200 250 _OO 350
TUBELENGTH,m (FromRef.5)
I i 1 1 1 1 1 1 1 1 1 1 1 " 1 " "I 1 _ "" 1 1) J .,
ECLSS TECHNOLOGYFOR SPACESTATIONEVOLUTION FIRE AND TOXIC
TOPICS JANUARY 1_19, 1990 GASDETECTION
RECOMMENDATIONS'.
1 PERFORM DETAILED ESTIMATES OF SENSING TUBE TRANSIT TIMES
m AND PARTICULATELOSSESFOR VARIOUSSENSORSCENARIOS.
2. REVIEW CURRENTLY AVAILABLE SMOKE DETECTORS AND GAS
DETECTORS (e.g., CO 2 , CO, H 2) FOR USE WITH THE CENTRALIZED
m DETECTOR/MONITORCONCEPT.
3. ASSESS VIABILITY OF GC/MS SMOKE-GAS DETECTION IN THE
z CENTRALIZEDDETECTOR/MONITORCONCEPT.O
r
_- 4. CONSTRUCTAND TEST A BREADBOARDSYSTEM FOR EVALUATIONOF
m THIS CONCEPT.
5. ESTABLISH SYSTEM OPERATIONAL REQUIREMENTS FOR SPACE
STATIONFREEDOMUSE.
6. ENCOURAGETHE DEVELOPMENTOF VERY SMALL, SOLID-STATE GAS
DETECTORSFOR SPACECRAFTUSE.


Increased Fire and Toxic Contaminant Detection Responsibility by Use of Distributed, Aspirating Sensors

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