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Copyright© 1995-2008 Underwriters Laboratories Inc. All rights reserved. No portion of this material may be reprinted in any
form without the express written permission of Underwriters Laboratories Inc. or as otherwise provided in writing.
Smoke Characterization Study
October 29, 2008
Paul E. Patty, P.E.
Senior Research Engineer
Northbrook, IL
847-664-2752
CANADIAN FIRE ALARM ASSOCIATION An Update on Standards, Technologies and
Solutions
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Overview
• What is Smoke – Quality Of Smoke
• How Do Detectors Work – Ionization
– Photoelectric
– Dual Technology
• Smoke Characterization Project – Material characteristics
– Smoke movement
– Photo/Ion response
• Development of Flaming & Smoldering Polyurethane Tests
– Flaming
– Smoldering
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What is Smoke
• Quality of smoke
– Color
• black, grey, yellow, white
– Particle size
• .01-10 microns
– Velocity
• > 32ft/min.
– Temperature
• <150 degrees F
– Build-up rate
• obscuration %/ft/min.
– Gases of combustion
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How Do Detectors Work Ionization Chamber Technology
.01 – 1 Microns
Ionization alarms respond to the near invisible particles of combustion. When a sufficient number of properly
sized particles enter the chamber the output of the chamber shifts enough to cause the alarm to activate.
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How Do Detectors Work Photoelectric Chamber Technology
.1 – 10 Microns
Photoelectric light scattering alarms respond to the visible particles of combustion. When a sufficient number
of properly sized particles enter the chamber the output of the chamber shifts enough to cause the alarm to
activate. Light scatting technology is also impacted by the color of the smoke that can reduce the output
signal of the alarm as the color of the smoke darkens.
Light Scattering
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How Do Detectors Work Dual Technology (Multicriteria) Operation
.01 – 10 Microns
1. Heat
2. Gas
3. Independent
Operation
4. Signal
Integration
Dual Technology/Multicriteria alarms monitor for several products of combustion, and make the
decision to activate based on these inputs. These types of alarms either monitor these inputs
separately, or combine the signals in an effort to make a better decision of differentiating between a
real fire signature, and a nuisance signature that can not be differentiated when only using an
individual technology.
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Alarm Sensitivity
Alarm Technology
Flaming Fire Response Time
(seconds)
Smoldering Fire Response Obscuration
(%/ft) Beam MIC
Wood Paper Heptane Wood (%/ft) (pa)
Ionization 170 133 49 8.14 (58.5 min.) 1.55 56.72
Photoelectric 197 147 103 3.71 (50.5 min.) 2.98 43.6
Photo/Ion 202 127 70 4.11 (52 min.) 3.09 45.13
Production Ionization 142 133 35 6.28 (56.3 min.) 1.6
Production Photoelectric 172 150 70 5.47 (55.06 min.) 2.5
Typical Response to Test Fires
a. Measured in ANSI/UL 217/268, CAN/ULC-
S529/S531smoke box.
b. Measuring Ionization Chamber measurement in
ANSI/UL 217/268, CAN/ULC-S529/S531 smoke box.
a b
Ionization alarms respond quicker to flaming fires, while photoelectric alarms respond quicker to non-
flaming fires.
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Living Room Fire
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UL-FPRF Smoke Characterization Study
• Launched to fill gaps in previous technical studies and to answer questions raised in actual fire events - essentially a “back to basics” investigation. Reduced evacuation times, and questions regarding the quality of smoke.
• Focused on 26 common materials (and combinations) found in the home, in non-flaming (smoldering) and flaming fires.
• UL purchased state of the art particle size equipment and developed new protocols for measuring smoke.
• Study took 1 year to design, 2 years to complete and cost $700,000. The entire report (with graphs and plots) is more than 3,000 pages.
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Objective and Scope
1. Develop smoke characterization analytical test
protocol using flaming and non-flaming modes of
combustion on selected residential materials.
2. “Fingerprint smoke” by developing smoke particle
size distribution data, chemical signatures and smoke
profiles for materials found in residential settings for
both flaming and non-flaming modes of combustion.
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Objective and Scope
3. Provide data and analysis to the industry for several
possible initiatives:
A) Develop recommendations to the current residential smoke
alarm standards CAN/ULC-S531 (ANSI/UL 217).
B) Provide data to the industry for the development of new
smoke sensing technology.
C) Provide data to the materials and additives industry to
facilitate new smoke suppression technologies and
improved end products.
D) Provide education to the fire community.
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Technical Plan
1. Characterize samples
– Material chemistry: FTIR-ATR
– Physical construction: Density, Size, etc.
– Thermal properties: DSC, TGA
2. Evaluate material specific combustion properties for effects of
material chemistry, physical construction, and combustion
mode
– Ignition time, Heat and Smoke release rates, Weight consumption
rate, Particle size and count distribution, Effluent gas: ASTM E1354
cone calorimeter coupled to particle and gas analyzers
3. Evaluate combustion properties for multi-component products
• Heat and Smoke release rates, Particle size and count distribution, Effluent gas: Intermediate-scale calorimeter coupled to particle and gas analyzers
4. Evaluate generated smoke and gases, alarm signal and response time in UL 217/268 Fire Test Room tests.
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Smoke Characterization Project: Findings
• Residential materials showed dramatically different heat and smoke release and smoke particle size behavior with non-flaming and flaming fires.
– Synthetic materials (e.g. polyethylene, polyester, nylon, polyurethane) generate higher heat and smoke release rates than the natural materials (e.g. wood, cotton batting).
– Flaming fires produce smaller mean smoke particles, non-flaming fires produce larger mean smoke particles.
– Photoelectric alarms triggered earlier for low-energy non-flaming fires.
– Ionization alarms triggered earlier for flaming and high-energy non-flaming fires.
• Smoke particles aggregate over time and distance from origin of ignition.
• Smoke from low energy, non-flaming fires may stratify as it rises and not reach to the ceiling.
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Smoke Characterization Project Sampling Method
N2
dilution
FTIR
Every 15 s
Smoke Particle
Every 67 s
Calorimeter
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Smoke Characterization Project Smoke Particle Analyzer Data
PET Carpet
11
17
26
40
63
10
2
16
9
29
7
36
0
44
5
57
5
90
0 048
115182
249316
383450
517584
0.0E+00
2.6E+05
5.1E+05
7.7E+05
1.0E+06
1.3E+06
Pa
rticle
de
nsity
(1/c
c)
Particle Size (nm)
Time (s)
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Smoke Characterization Project Key Findings - Gas Analysis
• Smoke Gas Effluent Composition - Gas effluent analysis
showed the dominant gas components were water vapor,
carbon dioxide and carbon monoxide.
Water CO2 CO
SO2 NO2 Methane
Ammonia Phenol SiF4
Formaldehyde HCN Propane
HCl HF Ethylene
Acrylonitrile Styrene
p/17
General Smoke Characteristics
Material Particle Size Particle Count Specific Extinction Area
(Microns) (m2/g) (Total Smoke Gen.
/weight loss)
Cooking Oil/Lard .08 2E+6 (2 Million) > .7
Douglas Fir .13 - .17 < .5E+5 < .35
Heptane/Toluene .19 - .30 1.72E+5 – 1.20E+6 < .35
Newspaper .17 - .18 < 1E+6 < .35
Polyurethane Foam .08 - .27 2E+6 (F) – 2.75E+6 (S) .08 (F) - .9 (S)
Ponderosa Pine .17 - .27 < 1.5E+5 < .35
Human Hair 50 – 100
During the various stages of a fire each material will generate unique particle sizes and count, and will
generate different quantities of smoke. The response of an alarm will vary based on the material, and how it
burns.
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d, Particle Size
Rela
tive S
ign
al S
en
sit
ivit
yParticle Size Influence on Sensing Technology
Obscuration ~ d3
Scattering ~ d2
Ion ~ d
Physics of ionization technology is linearly
responsive to particle size.
Physics of light-based technologies are more
responsive to larger particles than smaller
particles.
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Smoke Detector Performance Smoke movement
• Smoke Stratification - Non-flaming fires result in
changes in the smoke build up over time, such that
stratification of smoke below the ceiling occurs. This
time-dependent phenomenon results in less obscuration
at the ceiling than below the ceiling. This caused both
detection technologies to drift out of alarm.
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Smoke movement Key Findings - Fire Test Room
• Before Before
• After
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Smoke movement
0
2
4
6
8
10
12
0 1000 2000 3000 4000 5000 6000 7000
Time (sec)
OB
S (
%/f
t)
4 in below ceiling
24 in. below ceiling
36 in. below ceiling
60 in below ceiling
PU foam in Poly
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Material of Interest (STP follow-up activity)
• Polyurethane – Higher heat release rate (flaming)
– Higher smoke release rate (smoldering)
– Smaller black particles (flaming)
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Polyurethane Flaming Fire
Video
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New flaming & smoldering polyurethane tests:
• Develop new flaming and smoldering polyurethane (PU) foam
fire tests to compliment existing UL 217 and 268 tests.
Increase available egress time for non-specific fires by expanding
alarm responsiveness to other smoke signatures.
• Rationale
– Flaming PU foam generates smaller smoke particles than the
current fire tests.
– Synthetic materials generate greater heat and smoke release rates
than natural materials.
– Prevalence of PU foam in residential settings (mattresses,
upholstered furniture, etc.).
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“Standard” Foams Currently Used
Product Test Method Foam Test Material Description
Smoke
detectors
EN 54-7,
ISO 12239
“Soft polyurethane foam”
- No fire retardant
- Density: c. 20 kg/m3
Upholstered
furniture
ASTM E 1353,
CPSC 1634
SPUF: Polyurethane foam
- No inorganic fillers or FR
- Density: 28.8 ±1.6 kg/m3 (1.8 ±0.1 lb/ft3)
CA TB117+,
CPSC 1634
SFRPUF: Flame-retardant polyurethane foam
- Density: 22.4 ±1.6 kg/m3 (1.4 ±0.1 lb/ft3)
UFAC
Polyurethane foam
- No inorganic fillers or FR
- Density: 24.0 ± 1.6 kg/m³ (1.5 ± 0.1 lb/ft³)
Residential
sprinklers UL 1626
Polypropylene oxide polyol, polyether foam
- Density: 27.2 - 30.4 kg/m3 (1.70 - 1.90 lb/ft3)
- PHRR at 30 kW/m2: 230 ±50 kW/m2
- HOC at 30 kW/m2: 22 ±3 kJ/g
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Scenario Development
• Task Objectives: – Investigate influence of scenario variables on combustion
products.
– Develop smoke particle size and gas effluent data on the
scenarios.
Test Parameters:
Variables Output
Foam density
Sample size & shape Smoke build-up rate
Heating method
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Flaming Fire Scenarios
• Goal: – Flaming foam test that achieves obscuration levels similar to the
UL 217 flaming tests in a comparable time frame.
• Potential Scenarios: – EN 54-7 TF 4 flaming foam test
– Variations in foam density, sample size & shape, ignition point
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Flaming Fire Scenarios
2 step burning process:
• Flame front
• Molten sample
Variables:
• Foam density
• Sample size & shape
• Ignition point
Completed:
• 26 Calorimeter tests
• 22 Fire Room tests
Flame-out ranged from
260 to 2129 s
10 %/ft Obs reached in
85 to 1540s & never
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Polyurethane Flaming Test Sample
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Smoldering Fire Scenarios
• Goal: – Smoldering foam test that:
• Achieves 10 %/ft obscuration at 45 min.
• Achieves 12-15 %/ft obscuration by 60 min.
• Avoids settling/stratification (test < 75 min.).
• Potential Scenarios:
– Radiant panel: Heat from sample top surface
– Hot plate: Heat from sample bottom surface
– Cigarette ignition: Heat from sample top surface but
covered
– Hot wire: Heat from sample center
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Smoldering Fire Scenarios Radiant Panel
Variables:
• Fuel mass
• Rheostat level
Completed:
• 22 Calorimeter tests
• 30 Fire Room tests
10 %/ft Obs reached
412 to 2936s & Never
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Smoldering Fire Scenarios Hot Plate
Variables:
• Fuel mass
• Sample shape
• Heating profile
Completed:
• 26 Calorimeter tests
• 10 Fire Room tests
10 %/ft Obs reached
1788 to 2620s & Never
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Smoldering Fire Scenarios Hot Plate
0
2
4
6
8
10
12
14
16
18
0 600 1200 1800 2400 3000 3600
Time (s)
Obsc
ura
tion (
%/f
t)
F125 Alt. 1
F125 Alt. 2
F180 VF500 • Lower obscuration observed
for lower heating rates.
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Summary
• Gaps in previous research lead to Smoke
Characterization Project.
• Smoke Characterization Project findings lead to work
to improved response of alarms and detectors to non-
specific fires.
• UL is working with both national and international
experts to address these issues.
