Smoke Alarm Research at NIST
Thomas G. Cleary Fire Research Division
National Institute of Standards and Technology Smoke Alarm Summit
March 31, 2015
Outline
• Supporting ANSI/UL 217–268 Task Group on adding smoldering and flaming polyurethane foam fire tests.
• Cooking nuisance alarm scenarios and down-selection for further study.
• Future research
Genesis of Proposed New Fire Tests for ANSI/UL 217- 268
Based upon the results of FPRF Smoke Characterization Project
(2007), the following items were identified for further consideration:
• The addition of other test materials such as polyurethane foam in the flaming and non-flaming combustion modes in UL 217.
• Whether a smoke alarm, once triggered, should remain activated unless deactivated manually.
• Requiring the use of combination ionization and photoelectric alarms for residential use in order to maximize responsiveness to a broad range of fires.
• Characterize materials described in UL 217 using a cone calorimeter, smoke particle spectrometer, and analytical testing.
Analysis of Full-scale Experiments to Aid Selection of New Fire Test Criteria
• Estimate proposed alarm activation times and corresponding ceiling smoke obscurations for flaming and smoldering fire scenarios subject to ASET and RSET assumptions for a desired performance metric.
• Relate the ceiling smoke obscurations for flaming and smoldering scenarios to the performance criteria for the flaming and smoldering polyurethane foam test fires.
NIST Smoke Alarm Sensitivity Study (2008) • Follow-on to NIST Home Smoke Alarm Project (Dunes II). • Ignition sources were more realistic and had a lower
energy input into furniture mockups than Dunes II. – Initially flaming fires grew at medium “t2” fire growth rates (NFPA
72 definition) after a linear growth period up to ~25 kW typically lasting 3 to 4 minutes (based on mass loss measurements during tests and experimentally-determined heat of combustion).
– Initially smoldering fires upon transition to flaming grew at medium “t2” fire growth rates (except for one characterized as fast) after a smoldering period lasting from 81 to 182 minutes.
• Fires progressed much further before suppression than the Dunes II tests in order to achieve multiple tenability limits throughout the test structure.
Test Structure The fire tests were conducted in a building mock-up designed to represent a portion of an apartment or small home
Fire Fire
Bedroom Living Room
Kitchen
15.8 m
4.9 m
x x
x x c
cc
S5S6
S4 S3
S2 S1hf
DoorLaser ExtinctionLaser
Extinction
Laser Extinction
X - thermocouple tree location hf - total heat flux gage (1.5 m above the floor and pointing toward the fire) S1…S6 - alarm set location c - gas sampling location (1.5 m above the floor) dashed line - beam path for extinction measurements (1.5 m above the floor)
Smoke alarms were mounted four across on panel boards in random order P1 photoelectric I1 Ionization D1 dual alarm D2 dual alarm
Analyzing the Data ASET/RSET Concepts
• Available Safe Egress Time - ASET is the time to reach a threshold tenability limit on either combustion gas exposure, thermal exposure, or smoke concentration
• Required Safe Egress Time – RSET is the time it takes
for occupants to egress. It depends on pre-movement activities, travel distance and speed
Installed smoke alarms should provide early enough warning such that ASET > RSET
ASET/RSET Concepts
Ignition Alarm Tenability Limit
RSET Timeline
ASET
Margin of Safety
Master Bedroom
(MBR)Living Room
(LR)
Kitchen
Bedroom(BR)
Door(closed)
Door(open or closed)
Exit
3.7 m
8.9 m
3.0 m
4.0 m
ChairMock-up
ChairMock-up
4.0 m
Analysis Assumptions and Limitations
• Interconnected smoke alarms that alert occupants regardless of initial fire location.
• Occupant pre-movement time treated as a distribution for distinct populations.
• Travel speed as a function of smoke density. • Occupants traversing a range of equally frequent pre-
determined egress routes. • Considered only one apartment-sized residential space. • One location for the responsive smoke alarm. • Three flaming and three smoldering scenarios, and a total
of 18 full-scale tests.
Sample Computations for More Vulnerable/Slower Population
0
0.2
0.4
0.6
0.8
1
0
5
10
15
20
0 50 100 150 200 250 300
0.200.250.300.43None
Obsc.
Frac
tion
of S
ucce
ssfu
l Esc
apes
Smok
e O
bscu
ratio
n at
the
Cei
ling
(%/ft
Obs
c.)
Time to Alert from Start of Fire (s)
OD Limit (m-1)
0
0.2
0.4
0.6
0.8
1
0
5
10
15
20
25
30
35
40
2000 2500 3000 3500 4000 4500 5000
0.200250.300.43None
Obsc.
Frac
tion
of S
ucce
ssfu
l Esc
apes
Smok
e O
bscu
ratio
n at
the
Cei
ling
(%/ft
Obs
c.)
Time to Alert from Start of Fire (s)
OD Limit (m-1)
Flaming Fire/Living Room Smoldering Fire/Bedroom
Matched pairs of flaming and smoldering fire performance criteria where the average success rate is nominally equal for smoke
obscuration target values on the same row
Flaming fire test alarm criterion
Smoldering fire test alarm criterion
Smoke Obscura6on (%/: obsc.)
Averaged success rate and standard devia6on (%/%)
Smoke Obscura6on (%/: obsc.)
Averaged success rate and standard devia6on (%/%)
2* 94.3/5.7 12* 93.0/4.4
4 86.0/11.4 14 86.0/11.6
5 79.0/14.1 16 80.8/16.5
6 71.8/17.0 20 69.0/19.7
8 59.8/19.1 22 58.8/20.0
10** 49.0/19.1 24** 45.3/21.7
*Matched performance achievable with combination photoelectric/Ionization alarm **Current standalone photoelectric and ionization alarms would most likely pass with these criteria
NIST/CPSC Cooking Nuisance Tests • Cooking scenarios consisted of:
– broiling a hamburger – broiling frozen pizza – frying a hamburger – making a grilled-cheese sandwich in a no-stick frying pan – stir-frying vegetables in a wok on the electric burner – frying bacon – toasting bread
• Light, medium, and dark toast
– toasting frozen bagels
Alarm activation frequency for equal fractions
of range top, oven and toasting activities
0
0.2
0.4
0.6
0.8
1
0 1 2 3 4 5 6 7
P1 I1 D1 D2 M1 M2
Ala
rm A
ctiv
atio
n Fr
eque
ncy
Distance from Cooking Source (m)
NIST/CPSC Cooking Nuisance Tests
0.02
0.04
0.06
0.08
0.1
0
5 104
1 105
1.5 105
2 105
2.5 105
3 105
3.5 105
4 105
0 100 200 300 400 500 600 700
Toasting Bagel
AMDConc
Arit
hmet
ic M
ean
Dia
met
er (µ
m)
Tota
l Len
gth
(µm
/cm
3 )
Time (s)
0.2
0.4
0.6
0.8
1
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 100 200 300 400 500 600 700
Toasting Bagel
MMDConc
Mas
s M
ean
Dia
met
er (µ
m)
Mas
s C
once
ntra
tion
(mg/
m3 )
Time (s)
NIST/CPSC Cooking Nuisance Tests
0.02
0.04
0.06
0.08
0.1
0
5 104
1 105
1.5 105
2 105
2.5 105
0 100 200 300 400 500 600 700 800
Grilled Cheese Sandwich
AMD
Conc
Arit
hmet
ic M
ean
Dia
met
er (µ
m)
Tota
l Len
gth
(µm
/cm
3 )
Time (s)
0.2
0.4
0.6
0.8
1
0
1
2
3
4
5
6
0 100 200 300 400 500 600 700 800
Grilled Cheese Sandwich
MMD
Conc
Mas
s M
ean
Dia
met
er (µ
m)
Mas
s C
once
ntra
tion
(mg/
m3 )
Time (s)
NIST/CPSC Cooking Nuisance Tests
Source
Arithmetic Mean Diameter (µm)
Mass Mean Diameter (µm)
Toast 0.055 0.28
Bagel 0.045 0.2
Baking Pizza 0.053 0.19
Broiling Hamburger 0.09 0.45
Grilled Cheese Sandwich 0.075 0.57
Frying Bacon 0.085 0.57
Frying Hamburger 0.065 1.0
Stir Frying Vegetables 0.075 1.3
Results from single tests, mean values at peak concentration
Future Research • Characterize the existing and proposed fire tests and
nuisance tests for ANSI/UL 217 and ANSI/UL 268. – Measure the performance of a range of alarms on the market to
the existing and new proposed tests.
– Characterize smoke concentrations, particle sizes, light scattering signals, CO and CO2 gas concentrations and air temperatures for the existing and proposed fire and nuisance tests.
– Explore a performance rating system for smoke alarms
• Analyze fire and nuisance test data to suggest sensor combinations for discriminating smoke alarms.
Multi-angle, Multi-wavelength Light Scattering A portable, combination nephelometer and polarimeter has been constructed to measure light scattering characteristics of fire smokes and nuisance source aerosols. Characterization of smokes and nuisance aerosols may provide the data needed to develop advanced discriminating detectors that use multiple light scattering measures alone or combined with other sensor measurements..
Rotating Stage Polarimeter
Wavelength Choices 405 nm 635 nm 850 nm