Fire Safety Engineering & Structures in Fire
Workshop at Indian Institute of Science
9-13 August, 2010
Bangalore
India
Fire Safety Engineering Methods
Session JT9
Organisers:
CS Manohar and Ananth Ramaswamy
Indian Institute of Science
Speakers:
Jose Torero, Asif Usmani and Martin Gillie
The University of Edinburgh
Funding and
Sponsorship:
Smoke Detection
Detection
♦ Most obvious mechanism of early warning
♦ Types of detectors:
– Smoke Detectors (soot particles)
– CO detectors
– Temperature detectors
– Multiple-inputs (artificial inteligence systems)
– etc
♦ We will discuss smoke detectors
Background (I)
♦ For more than 40 years the fire literature has dedicated
numerous studies to the understanding of “smoke”
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Foster, W.W., “Attenuation of Light by Wood Smoke,” British Journal of Applied
Physics, Vol. 10, pp. 416-420, 1959.
Seader, J.D., and Einhorn, I.N., “Some Physical, Chemical, Toxicological, and
Physiological Aspects of Fire Smokes,” 16th Symposium (International) on
Combustion, Proceedings, The Combustion Institute, pp. 1423 – 1445, 1977.
Seader, J.D., and Ou, S.S., “Correlation of the Smoking Tendency of Materials,” Fire
Research, Vol. 1, pp. 3-9, 1977.
Clark, F.R.S., “Assessment of Smoke Density with a Helium-Neon Laser,” Fire and
Materials, Vol. 9, No. 1, pp. 30-35, 1985.
Mulholland, G.W., “Smoke Production and Properties,” SFPE Handbook of Fire
Protection Engineering, 2nd ed., DiNenno, P.J., Ed., National Fire Protection
Association, Quincy, MA, pp. 2-217-2-227, 1995.
Dobbins, R.A., Mulholland, G.W., and Bryner, N.P., “Comparison of a Fractal Smoke
Optics Model with Light Extinction Measurements,” Atmospheric Environment, Vol.
28, No. 5, pp. 889-897, 1994.
Mulholland, G.W., and Croarkin, C., “Specific Extinction Coefficient of Flame
Generated Smoke,” Fire and Materials, Vol. 24, pp. 227-230, 2000.
Background (II)
♦ For more than 20 years the fire community has tried to establish a
coherent metric to assess the performance of smoke detectors.
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Levine, R., “Detection and Smoke Properties,” U.S./Japan Cooperative Program on Natural
Resources, Panel on Fire Research and Safety, Vol. 6, Oct. 19-22, Tokyo, Japan, pp. 1 – 31, 1976.
Lee, T.G.K., and Mulholland, G. “Physical Properties of Smokes Pertinent to Smoke Detector
Technology,” NBSIR 77-1312, National Bureau of Standards, Gaithersburg, MD, pp.2, 1977.
Heskestad, G., “Generalized Characterization of Smoke Entry and Response for Products-ofCombustion Detectors,” Fire Protection for Life Safety Proceedings of a Symposium, March 31April 1 1975, National Academy of Sciences, Washington, D.C., pp. 93-12, 1977.
Mulholland, G.W., and Liu, B.Y.H., “Response of Smoke Detectors to Monodisperse Aerosols,”
Journal of Research of the National Bureau of Standards, Vol. 85, No. 3, pp. 223 – 237, 1980.
Mulholland, G.W., “How well are we measuring smoke?” Fire and Materials, Vol. 6, No. 2, pp. 6567, 1982.
Schifiliti, R.P. Meacham, B.J., and Custer, R.L.P., “Design of Detection Systems,” SFPE
Handbook of Fire Protection Engineering, 2nd ed., DiNenno, P.J., Ed., National Fire Protection
Association, Quincy, MA, 1995, p. 4-16.
Grosshandler, W.L., “Progress Report on Fire Detection Research in the United States,”
U.S./Japan Government Cooperative Program on Natural Resources (UJNR), 13th Joint Panel
Meeting, March 13 – 20, 1996, Giathersburg, MD, Vol. 2, Beall, K.A., Ed., pp. 363-369, 1997.
Bukowski, R.W., and Reneke, P.A., “New Approaches to the Interpretation of Signals from Fire
Sensors,” Sensors Expo, Proceedings, Baltimore, MD, Helmers Publishing, Inc., Peterborough,
NH, pp. 291-298, 1999.
Mulholland, G.W., Johnsson, E.L., Fernandez, M.G., and Shear, D.A., “Design and Testing of a
New Smoke Concentration Meter,” Fire and Materials, Vol. 24, pp. 231-243, 2000.
Background (III)
♦ Multiple standards have been developed (i.e.)
– Underwriters Laboratories Inc., “Standard for Safety 268: Single and
Multiple Station Smoke Alarms,” 5th Ed., Underwriters Laboratories
Inc., Northbrook, IL, 1997.
– Underwriters Laboratories Inc., “UL Standard for Safety for Single and
Multiple Station Smoke Alarms, UL 217,” 5th Ed., Underwriters
Laboratories Inc., Northbrook, IL, 1997.
♦ Nevertheless, there is a common believe that no
metric seems to provide a comprehensive
assessment of detector performance
♦ Our discussion will only deal with the principles of
smoke detection
Background (IV)
♦ Smoke characteristics are a function of many
things:
• Fire size
• Fuel
• Ventilation
• Burning characteristics
• Agglomeration rates (flow conditions,
acoustic fields)
Examples
n-Heptane-45 cm
pan
Polyurethane
Foam
Smoldering
newspaper
Background (V)
From Mulholland, SFPE Handbook, 1995
Smoke Detectors
Ionization
Photoelectric
Background (V)
+
IO
V
V=f(dp, N (strong))
Ionization
Detectors
Light
Obscuration
Measurement
IT=f(l,sdp, N)
IT
IA
IS
Photoelectric
Detectors
IS=f(l, dp (strong), N)
♦ Currently, light
obscuration is used
as the main
parameter to define
detector
performance
UL-217- “Smoke Box”
Obscuration
IO  I
obscuration% 
*100
IO
I0 – initial light intensity
Optical Density
I  I O exp( CL)
De – optical density
– extinction coefficient
 I
De   log e 
 IO

  CL

C – particle mass
concentration
L - distance
Fuel
Optical Density at Full Ionization Detector Output
Optical Density at Full Photoelectric Detector Output
0.2
0.16
Toluene
Newspaper (smoldering)
Heptane/Toluene Mixture
PU Foam
Newspaper (flaming)
0.1
Toluene
Newspaper (smoldering)
Heptane/Toluene Mixture
0.18
0.16
-1
Optical Density (m )
0.12
-1
Optical Density (m )
0.14
0.08
0.06
0.04
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0.02
0
0
0
0.5
1
3
Flow Rate (m /s)
1.5
0
0.5
1
3
Flow Rate (m /s)
1.5
Background (VI)
-1
Fraction of Full Detector Response for D = .01 m
0.5
Photoelectric average
Ionization average
Fraction of Full Detector Response
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
Smoldering
Newspaper
Toluene
Heptane/Toluene
Mixture
Fuel
Heptane
Effect of Fire Size (II)
Energy Release Rate
15 cm Toluene Fire at 3/4 Flow
35
Mass Optical Density
15 cm Toluene Fire at 3/4 Flow
25
20
15
0.3
10
Mass Optical Density (m /g)
Energy Release Rate (kW)
30
0.25
2
5
0
00:00.0
01:00.0
02:00.0
03:00.0
04:00.0
05:00.0
06:00.0
Time (MM:SS)
Optical Density and Photoelectric Detector Response
15 cm Toluene Fire at 3/4 Flow
1
Optical Density
Photoelectric Detector
-1
Optical Density (m )
0.18
0.9
0.16
0.8
0.14
0.7
0.12
0.6
0.1
0.5
0.08
0.4
0.06
0.3
0.04
0.2
0.02
0.1
0
00:00.0
01:00.0
02:00.0
03:00.0
Time (MM:SS)
04:00.0
05:00.0
0
06:00.0
Fraction of Full Detector
Response
0.2
0.2
0.15
0.1
0.05
0
00:00.0
01:00.0
02:00.0
03:00.0
Time (MM:SS)
04:00.0
05:00.0
06:00.0
Effect of Fire Size (I)
I  I O exp( CL)
Dm 
s s ys
2.303
Mass Optical Density
♦ Serves to scale the Optical
density by the mass burning
rate (i.e. Energy Release
Rate)
♦ Assumes that the specific
extinction coefficient (ss)
and soot yield are not
dependent with fuel size.
Effect of Fire Size (III)
Reference
♦ Particulate Entry Lag in Spot-Type Smoke Detectors, Cleary, T. G.;
Chernovsky, A.; Grosshandler, W. L.; Anderson, M.
Fire Safety Science. Proceedings. Sixth (6th) International Symposium.
International Association for Fire Safety Science (IAFSS). July 5-9,
1999, Poitiers, France, Intl. Assoc. for Fire Safety Science, Boston, MA,
Curtat, M., Editor, 779-790 pp, 2000.
♦ www.bfrl.nist.gov
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Go to publications
Author
Cleary
You will find a list of his publications and a link to a pdf of the above paper