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

NIST/CPSC Cooking Nuisance Tests

NIST/CPSC Cooking Nuisance Tests

8.6 m

4.4 m

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

Thank you for your attention