Smoke Alarm Research at NIST

Transcription

1 Smoke Alarm Research at NIST Thomas G. Cleary Fire Research Division National Institute of Standards and Technology Smoke Alarm Summit March 31, 2015

2 Outline Supporting ANSI/UL Task Group on adding smoldering and flaming polyurethane foam fire tests. Cooking nuisance alarm scenarios and downselection for further study. Future research

3 Genesis of Proposed New Fire Tests for ANSI/UL 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.

4 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.

5 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 t 2 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 t 2 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.

6 Test Structure The fire tests were conducted in a building mock-up designed to represent a portion of an apartment or small home 15.8 m 4.9 m Bedroom S6 S5 Kitchen x hf Living Room S2 x c S1 Laser Extinction Fire Laser Extinction x c Door S4 x c S3 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) Fire Smoke alarms were mounted four across on panel boards in random order P1 photoelectric I1 Ionization D1 dual alarm D2 dual alarm

7 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

8 ASET/RSET Concepts Chair Mock-up Master Bedroom (MBR) 4.0 m Kitchen Door (open or closed) 3.7 m 8.9 m Living Room (LR) Chair Mock-up 3.0 m Door (closed) 4.0 m Bedroom (BR) Exit Timeline RSET ASET Margin of Ignition Alarm Safety Tenability Limit

9 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 predetermined 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.

10 Sample Computations for More Vulnerable/Slower Population Flaming Fire/Living Room Smoldering Fire/Bedroom Fraction of Successful Escapes Obsc. OD Limit (m -1 ) None Time to Alert from Start of Fire (s) Smoke Obscuration at the Ceiling (%/ft Obsc.) Fraction of Successful Escapes OD Limit (m -1 ) None Obsc Time to Alert from Start of Fire (s) Smoke Obscuration at the Ceiling (%/ft Obsc.)

11 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 Smoke Obscura6on (%/: obsc.) Averaged success rate and standard devia6on (%/%) Smoldering fire test alarm criterion Smoke Obscura6on (%/: obsc.) Averaged success rate and standard devia6on (%/%) 2* 94.3/5.7 12* 93.0/ / / / / / / / / ** 49.0/ ** 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

12 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

13 NIST/CPSC Cooking Nuisance Tests

14 NIST/CPSC Cooking Nuisance Tests 8.6 m 4.4 m

15 Alarm activation frequency for equal fractions of range top, oven and toasting activities Alarm Activation Frequency P1 I1 D1 D2 M1 M Distance from Cooking Source (m)

16 NIST/CPSC Cooking Nuisance Tests Toasting Bagel Toasting Bagel Arithmetic Mean Diameter (µm) AMD Conc Total Length (µm/cm 3 ) Mass Mean Diameter (µm) MMD Conc Mass Concentration (mg/m 3 ) Time (s) Time (s)

17 NIST/CPSC Cooking Nuisance Tests Grilled Cheese Sandwich Grilled Cheese Sandwich Arithmetic Mean Diameter (µm) AMD Conc Total Length (µm/cm 3 ) Mass Mean Diameter (µm) MMD Conc Mass Concentration (mg/m 3 ) Time (s) Time (s)

18 NIST/CPSC Cooking Nuisance Tests Source Arithmetic Mean Diameter (µm) Mass Mean Diameter (µm) Toast Bagel Baking Pizza Broiling Hamburger Grilled Cheese Sandwich Frying Bacon Frying Hamburger Stir Frying Vegetables Results from single tests, mean values at peak concentration

19 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.

20 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..

21 Thank you for your attention