signature of the fire through the roof. For this limited set of burn experiments, the thermal
imagers did not appear to provide sufficient warning to allow fire fighters to escape before the
roof collapsed.

Cone Calorimeter Experiments

Three replicate tests of each sample were conducted in the cone calorimeter. Each sample was
exposed to either an external heat flux of 35 kW/m’ or 70 kW/m’. Based on an analysis of heat
flux data obtained by various researchers, Babrauskas recommends using a heat flux value of

35 kW/m’ for materials exposed to pre-flashover fires [16]. For post flashover fire exposure,
Babrauskas indicates potential heat fluxes as high as 150 kW/m’ could be required. This value is
beyond the capabilities of most laboratory scale apparatus including the cone calorimeter. In the
post flashover fire data analyzed by Babrauskas, heat flux values for exposures to ceiling
surfaces ranged from 67 to 147 kW/m. In research by Madrzykowski [17], a value of 70 kW/m
is suggested as providing cone calorimeter results similar to full scale performance for certain
materials.

2

For each test, the 0.1 m (0.3 ft) square sample was oriented horizontally under the cone heater.
Each sample was wrapped in aluminum foil on all sides except for the exposed surface and
placed in a metal frame. A number of flammability properties were measured including heat
release rate, specimen mass loss rate, smoke generation rate, combustion gas production, and
ignitability. The data obtained for each sample from the cone calorimeter tests is contained in
Appendix A. The average values for each sample at the two external heat fluxes are shown in
Table 2.

-13-


Figure 15. Photograph of test structure at 75 s after ignition.

-34-


Figure 11. Photograph showing trusses supporting the roof structure with thermocouple array
visible in front of second vertical wood member.

-30-


Figure 20. Photograph of test structure at 640 s after ignition.

-39-


combination of water and a fire suppression foam agent. The test sequence is depicted in Figures
14 through 24.

Test No. 1 was conducted using the structure with a roof composed of asphalt shingles over
plywood. For the first test, smoke became visible coming from the structure approximately 60 s
after ignition. At approximately 3 min after ignition, the living room reached flashover
temperatures. The bedroom reached flashover temperatures about 6 2 min after ignition. After
approximately 1 min, the temperatures in the living room dropped to a relatively uniform 500 °C
(930 °F). The bedroom temperatures remained near 600 °C (1110 °F). The fire appears to have
penetrated into the attic space at about 7 4 min after ignition. At 14 min, portions of the roof
began to burn. Collapse of a portion of the roof and removal of the firefighter mannequins
occurred 17 4 min after ignition. Fire suppression was initiated at 18 min 40 s.

Test No. 2 was conducted using the structure with a roof composed of asphalt shingles over
oriented strand board. In the second test, smoke became visible coming from the structure
approximately 52 seconds after ignition. At approximately 3 4 min after ignition, the living
room temperatures briefly exceeded flashover temperatures. Temperatures in the bedroom area
never exceeded the 600 °C (1110 °F) flashover threshold until near the end of the test. The
living room maintained peak temperatures in excess of 500 °C (930 °F) while the temperatures in
the bedroom remained between 400 °C (750 °F) and 600 °C (1110 °F). The fire appears to have
penetrated into the attic space at about 8 min after ignition. Flames began lapping the roof 13
min after ignition and the front door failed. At 14 min, portions of the roof began to burn.
Collapse of a portion of the roof and removal of the firefighter mannequins occurred 17 min after
ignition. Suppression was initiated at 17 min 45 s.

Test No. 3 was conducted using the structure with a roof composed of cementitious tile over
plywood. During the third test, smoke became visible coming from the structure approximately
1 min 20 s after ignition. At approximately 3 min after ignition, the living room reached
flashover temperatures of approximately 600 °C (1110 °F). The living room continued to
maintain temperatures in excess of 600 °C (1110 °F) for most of the test period. Temperatures in
the bedroom remained below flashover temperatures until 11 min after ignition. The fire appears
to have penetrated into the attic space again at 8 min after ignition. Collapse of a portion of the
roof and removal of the firefighter mannequins occurred 16 min after ignition. Suppression was
initiated at 17 min. White smoke was observed coming from the structure at 19 min 40 s.

Test No. 4 was conducted using the structure with a roof composed of cementitious tile over
oriented strand board. For the fourth test, smoke was first visible at approximately 56 s after
ignition. Flashover temperatures were reached in the living room 4 min after ignition while the
bedroom remained below flashover temperatures until almost 8 min after ignition. The fire
penetrated into the attic space at about 8 min after ignition. Collapse of a portion of the roof and
removal of the firefighter mannequins occurred 17 min 10 s after ignition. Suppression was
initiated at 18 min.


Appendix A
Cone Calorimeter Test Data

-67-


1200

Standing - Left
&— Standing - Right
1000 © ~~ Leaning - Left
---- Leaning - Right
800
S
©
5
® 600
Oo
Qa
€
Oo
fa
400
200
ot res,

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Figure 30. Graph showing temperatures measured on the roof under the fire fighter mannequins’
boots during the first test.

- 49 -


1200

1000

800
S
©
5

3 600
Oo
Qa
E
Oo
£

400

200

0

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Figure 28. Graph showing temperatures measured in the north portion of the attic during the first
test (distances measured from roof peak downward).

-47-


1200

1000
800

S

©

5

3 600

Oo

Qa

E

Oo

£
400
200

0 1 1

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Figure 34. Graph showing temperatures measured in the south portion of the attic during the
second test (distances measured from roof peak downward).

-53-


1200

1000

800

600

Temperature (°C)

400

200

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Figure 38. Graph showing temperatures measured in the north portion of the attic during the
third test (distances measured from roof peak downward).

-57-


1200

1000

800

600

Temperature (°C)

400

200

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Figure 26. Graph showing temperatures measured in the living room during the first test
(distances measured from ceiling downward).

-45 -


The temperature of the roof surface under the fire fighter mannequins’ boots did not increase
significantly prior to collapse. Temperature measurements obtained under fire fighter boots
would probably not be a useful indicator of potential collapse. Unfortunately, the fire fighter
mannequins did not move. Therefore, the influence of impact or dynamic loading from walking
on the roof could not be evaluated. Impact loads on these roof structures could result in
significantly less time to collapse.

Each of the roofs collapsed between approximately 16 % min and 17 % min. This limited set of
full-scale tests do not demonstrate significant difference between the performance of the
plywood and OSB sheathing. No differences were observed between the asphalt shingles and
the cementatious tiles. The other temperature data obtained during the tests did not indicate any
difference in performance between the plywood and OSB. OSB releases energy faster and more
of its total energy when exposed to high radiant heat fluxes in the cone calorimeter. While it is
heat flux dependent, both materials ignite after about the same exposure time.

This limited set of burn tests indicated that infrared cameras may not be a viable tool for
predicting structural collapse in residential structures. The thermal signature of the fire coming
through the roof is washed out by radiation from smoke or fire plumes or was obscured by water
spray or rain. Since one typically expects hot smoke or fire plumes as well as water sprays to be
present at residential fire scenes, thermal images do not appear to be an adequate indicator of
pending structural collapse.

Acknowledgements

The authors would like to thank the Phoenix Fire Department and Chief Alan Brunacini for
inviting NIST to participate in this live fire training exercise. Captain Tom Bates of the Phoenix
Fire Department deserves special recognition for the invaluable support that he provided to NIST
staff during this test series. In addition, the authors are grateful to Mr. Michael Smith of the
Building and Fire Research Laboratory at NIST for conducting the cone calorimeter tests. The
authors would like to thank Mr. Francis L. Brannigan, author of Building Construction for the
Fire Service, for providing comments on this report. Review of this document by the American
Forest and Paper Association is also appreciated. Finally, the authors express gratitude to the
United States Fire Administration and Mr. William Troup for their sponsorship and support of
this important research.

References

1] Beyler, C.L., “Fire Safety Challenges in the 21“ Century,” Journal of Fire Protection
Engineering, Vol. 11, No.1, pp. 4-15, 2001.

[2] Fire Fighter Fatalities in the United States in 1999, United States Fire Administration,
Emmitsburg, MD, July 2000.

-17-


_

Figure 16. Photograph of test structure at 120 s after ignition.

-35-


Figure 47. Test 3 shown approximately 10 s before collapse of the roof structure (top — normal
video, middle — fire department thermal imager, bottom — high end, quantitative infrared camera)

- 66-


Figure 1.
Figure 2.
Figure 3.
Figure 4.

Figure 5.
Figure 6.

Figure 7.
Figure 8.

Figure 9.

Figure 10.
Figure 11.
Figure 12.
Figure 13.

Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.

Figure 22.

Figure 23.
Figure 24.

Figure 25.
Figure 26.

List of Figures

Photograph showing the front and one side of test structure with tile roof
prior to start of test
Photograph showing rear and one side of test structure with asphalt single

roof prior to start Of teSt occ eeseseseseseeseseeseseensacsesnsacssscaearsacarensataeacaeeneaeere 21
Plan view of test structure showing approximate placement of furniture
and other items within structure (not to scale)... ceceseesesesseeseeseeeseeeeseeneeeeneeeeee 22

Plan view of test structure showing locations of measurement instruments
and dimensions (all dimensions in m)
Diagram showing typical construction of the test structure
Photograph showing living room ceiling with ceiling louvers, electrical
boxes, and attic access
Photograph of living room area showing furniture arrangement..
Photograph showing living room with furniture, cabinets, and

thermocouple array .........cesceecesesseseseeseeesseseseeseseesesesesscsesecaesesueseseaseesesenseenseneneeeeee 27
Photograph showing furniture in bedroom area of test structure

(thermocouple array is visible in the foreground.).............essesesesseeseeeseereseereneees 28
Photograph showing two double beds, night tables and lamps in the

DedrOOM oo. eeeesceseesees ees ces ees eeseeseeseeseesessesuesnesesesessessessesseesessessssuesesssesseeseeeeeneeeenee 29

Photograph showing trusses supporting the roof structure with
thermocouple array visible in front of second vertical wood member
Photograph of living room showing ignition location in corner of couch
under newspaper
Photograph showing bedroom with ignition location i in corner of chair
under the newspaper
Photograph of test structure at 60 s after ignitioi
Photograph of test structure at 75 s after ignition..
Photograph of test structure at 120 s after ignition
Photograph of test structure at 180 s after ignition
Photograph of test structure at 210 s after ignition
Photograph of test structure at 540 s after ignition
Photograph of test structure at 640 s after ignition
Photograph of test structure at 900 s after ignition when front door has
burned away
Photograph of test structure at 960 s after ignition with portion of roof
structure burning
Photograph of test structure at 1010 s after ignition as collapse is starting
Photograph of test structure at 1140 s after ignition when suppression has
been completed
Schematic drawing of the cone calorimeter.
Graph showing temperatures measured in the living room during the first

test (distances measured from ceiling downward)..........ccesseseesesesseeeeeeeeeeeneees 45

-iv-


wo 22-2 2--------------------- NIST/BFRL/MPG --------------------------------
C:\CONE171\RAWDATA\010731A2.CDT

Test Date : 31-Jul-01 Test Time : 01:01 p.m. Operator : Michael Smith

Test Scans
Test Length

203 scans, 3 secs/scan
487.16 secs

Sample Surface Area : 0.01000 m2
Radiant Heat Flux : 35.0 kW/m2
Sample Orientation : Horizontal
Measured Exh. Flow : 0.024 m3/sec
Orifice Plate : 57 mm
Sample Material :

External Oriented Strandboard

SAMP.2

Pre-test Comments:

Samp.in double density alumn.pan edge control.
Thermal absorber applied.
Samp.wt.=68.2g,Samp.t+tpan wt.=71.4g.

Post-test Comments:
Samp.exhibited a uniform combustion process
without any thermal anomalies to report.

aaa Reduction Parameters ---W--~-------- 9-993 -2n2nnnnnnnnnnnnnnnnnnn

C-Factor (Methane) : 0.04381603
Conversion Factor : 13.100 MJ/kg 02
Baseline 02 Reading : 20.983 %
Baseline C02 Reading : 0.05089 %
Baseline CO Reading : 0.00012 %

Sanaa” Test Results -------9--9 9-92 n nnn nnn nnn nnn nn nnn nnn nnn nnn

233.82 kW/m2 at 409.00 secs
161.66 kW/m2
164.92 kW/m2
154.49 kW/m2
144.87 kW/m2
74.28 MJ/m2
13.44 MJ/kg

Peak Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Total Heat Released
Average Effective HOC

Average Specific Ext Area : 65.55 m2/kg
Average Mass Loss Rate: H 12.369 g/s*m2
Entered Initial Specimen Mass : 71.40 g
Measured Final Specimen Mass : 16.12 g
Average CO Yield : 0.00223 kg/kg
Average C02 Yield : 1.44792 kg/kg
Time to sustained Ignition H 32.62 secs

-69-


wo 22-2 2--------------------- NIST/BFRL/MPG --------------------------------
C:\CONE171\RAWDATA\010731A1.CDT

Test Date : 31-Jul-01 Test Time : 13:38 p.m. Operator : Michael Smith

Test Scans
Test Length

238 scans, 3 secs/scan
592.94 secs

Sample Surface Area : 0.01000 m2
Radiant Heat Flux : 35.0 kW/m2
Sample Orientation : Horizontal
Measured Exh. Flow : 0.024 m3/sec
Orifice Plate : 57 mm
Sample Material :

External Oriented Strandboard

SAMP.1

Pre-test Comments:

Samp.in double density alumn.pan edge control.
Thermal absorber applied.
Samp.wt.=77.4g,Samp.t+tpan wt.=80.5g.

All samp.this series are 100mm X 100mm X 12mm

Post-test Comments:
Samp.exhibited a uniform combustion process

without any thermal anomalies to report.

aaa Reduction Parameters ---W--~-------- 9-993 -2n2nnnnnnnnnnnnnnnnnnn

C-Factor (Methane) : 0.04381603
Conversion Factor : 13.100 MJ/kg 02
Baseline 02 Reading : 20.984 3%
Baseline C02 Reading : 0.048183
Baseline CO Reading : 0.00012 %

Sanaa” Test Results -------9--9 9-92 n nnn nnn nnn nnn nn nnn nnn nnn nnn

224.27 kW/m2 at 484.00 secs
151.12 kW/m2
154.68 kW/m2
154.38 kW/m2
138.36 kW/m2
83.06 MJ/m2
13.24 MJ/kg

Peak Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Total Heat Released
Average Effective HOC

Average Specific Ext Area : 56.28 m2/kg
Average Mass Loss Rate: H 11.783 g/s*m2
Entered Initial Specimen Mass : 80.50 g
Measured Final Specimen Mass : 17.75 g
Average CO Yield : 0.00262 kg/kg
Average C02 Yield : 1.43264 kg/kg
Time to sustained Ignition H 48.51 secs

- 68 -


wo 22-2 2--------------------- NIST/BFRL/MPG --------------------------------
C:\CONE171\RAWDATA\010731A4.CDT

Test Date : 31-Jul-01 Test Time : 01:35 p.m. Operator : Michael Smith

Test Scans 247 scans, 3 secs/scan

Test Length : 621.95 secs
Sample Surface Area : 0.01000 m2
Radiant Heat Flux  : 35.0 kW/m2
Sample Orientation : Horizontal
Measured Exh. Flow : 0.024 m3/sec
Orifice Plate : 57 mm

Sample Material
External 5 PLY Plywood
SAMP.1

Pre-test Comments:

Samp.in double density alumn.pan edge control.
Thermal absorber applied.
Samp.wt.=63.6g,Samp.t+pan wt.=66.6g.

Post-test Comments:
Samp.exhibited a uniform combustion process
without any thermal anomalies to report.

aaa Reduction Parameters ---W--~-------- 9-993 -2n2nnnnnnnnnnnnnnnnnnn

C-Factor (Methane) : 0.04381603
Conversion Factor : 13.100 MJ/kg 02
Baseline 02 Reading : 20.984 3%
Baseline C02 Reading : 0.05404 %
Baseline CO Reading : 0.00011 %

Sanaa” Test Results -------9--9 9-92 n nnn nnn nnn nnn nn nnn nnn nnn nnn

220.48 kW/m2 at 454.00 secs
108.64 kW/m2
112.37 kW/m2

Peak Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate T60

Average Heat Release Rate 82.65 kW/m2
Average Heat Release Rate 86.52 kW/m2
Total Heat Released 63.26 MJ/m2

Average Effective HOC 12.80 MJ/kg

Average Specific Ext Area : 51.79 m2/kg
Average Mass Loss Rate: H 9.555 g/s*m2
Entered Initial Specimen Mass : 66.60 g
Measured Final Specimen Mass : 17.17 g
Average CO Yield : 0.00155 kg/kg
Average C02 Yield : 1.31432 kg/kg
Time to sustained Ignition H 40.71 secs

-71-


Figure 9. Photograph showing furniture in “bedroom” area of test structure. (A thermocouple
array is visible in the foreground.)

- 28 -


Table 2. Summary of Cone Calorimeter Data

Data Item 35. kW/m? 70 kW/m"
Plywood OSB Plywood OSB
Peak Heat Release Rate (kW/m’) 220 235 254 329
Time of Peak Heat Release Rate (s) 433 442 32 36
Average Heat Release Rate (kW/m*) 115 156 168 223
Average Heat Release Rate at 60s (kW/m’) 123 165 164 267
Average Heat Release Rate at 180 s (kW/m*) 93 156 157 231
Average Heat Release Rate at 300 s (kW/m*) 95 142 180 231
Total Heat Released (MJ/m”) 62 80 65 89
Average Effective Heat of Combustion (MJ/kg) 12.9 13.4 13.4 14.2
Average Specific Extinction Area (m‘/kg) 56 63.8 130.5 123.9
Average Mass Loss Rate (g/s/m*) 9.9 12.1 14.4 16.9
Initial Specimen Mass (g) 64.7 76.4 64.0 79.5
Final Specimen Mass (g) 16.8 17.0 16.0 16.9
Average CO Yield (kg/kg) 0.0016 0.0023 0.00344 | 0.00391
Average CO: Yield (kg/kg) 1.34 1.45 1.40 1.49
Time to Sustained Ignition (s) 47.1 39.7 717 10.6

As expected, the higher heat flux results in a more rapid ignition of both materials. It also leads
to greater production of smoke and combustion gases. At the higher heat flux, the OSB has a
peak heat release rate almost 100 kW greater than the peaks obtained from either material at

35 kW/m” and the plywood at 70 kW/m. The heat release rate for the OSB is approximately
100 kW greater than the other materials throughout the test at 70 kW/m’. While the plywood
mass was approximately 10 g less than the OSB at the start of each test, approximately the same
mass of material remained at the end of the test. The total amount of energy liberated per square
meter of material is significantly greater for the OSB than the plywood. The pyrolysis and
combustion of the organic binder, which represents a higher mass fraction in OSB relative to
plywood, would be consistent with a higher peak heat release rate.

Uncertainty Analysis

There are different components of uncertainty in the gas temperatures, mass of fuel packages,
and time to collapse data reported here. Uncertainties are grouped into two categories according
to the method used to estimate them. Type A uncertainties are those which are evaluated by
statistical methods, and Type B are those which are evaluated by other means [18]. Type B
analysis of systematic uncertainties involves estimating the upper (+ a) and lower (- a) limits for
the quantity in question such that the probability that the value would be in the interval (+ a) is
essentially 100 %. After estimating uncertainties by either Type A or B analysis, the
uncertainties are combined in quadrature to yield the combined standard uncertainty.

-14-



Figure 1. Photograph showing the front and one side of test structure with tile roof prior to start
of test.

-20-


Component Combined Total
Standard Standard Expanded
Uncertainty Uncertainty Uncertainty
Time to Collapse
Repeatability + 7% £9% +17%
Random +5%
Infrared Camera Temperatures
Zero +5%
Calibration +5%
Emissivity + 10% +17% +35%
Repeatabiltiy + 10%
Random +5%
Cone Calorimeter
Peak Heat Release Rate + 13% + 13% + 25%
Time of Peak Heat Release Rate + 4% + 4% + 8%
Average Heat Release Rate + 10% + 10% + 20%
Total Heat Released + 14% + 14% + 28%
Average Eff. Ht. of Combustion + 10% + 10% + 20%
Average Specific Extinction Area + 10% + 10% + 20%
Average Mass Loss Rate + 10% + 10% + 20%
Specimen Mass + 5% + 5% + 10%
Average CO Yield + 10% + 10% + 20%
Average CO; Yield + 10% + 10% + 20%
Time to Sustained Ignition + 5% + 5% + 10%
Note: Random and repeatability evaluated as Type A, other components as Type B.

Conclusions

For all four tests, the maximum temperatures in the living room and bedroom areas reached
between 540 °C (1000 °F) and 815 °C (1500 °F). Flashover occurred in the living room spaces
approximately 3 to 4 minutes after ignition. Prior to collapse, peak temperatures in the attic
spaces were approximately 500 °C (930 °F). The fires broke through into the attic spaces
between 6 minutes and 8 minutes after ignition. In all of the tests, collapse occurs approximately
17 minutes after ignition. Flashover in the attic spaces occurs approximately 5 % minutes after
the fire breaks through the ceiling or 12 minutes after ignition. As the attic space approaches
flashover, temperatures under the roof rapidly change (on the order of a few seconds) from near
ambient 37 °C (100 °F) to 540 °C (1000 °F).

- 16-


Figure 10. Photograph showing two double beds, night tables and lamps in the “bedroom”.

-29-


the attic space and failure of the ceiling membrane between the living room/bedroom area and
the attic. Once the attic space has flashed over at 900 s, the temperatures become uniform at
approximately 750 °C (1380 °F) until collapse at 1030 s. The temperature data obtained on the
roof surface beneath the fire fighter mannequin boots during the fire test is shown in Figure 45.
Very little temperature increase is evident on the underside of the fire fighter boots until the roof
collapses at 1030 s.

In all cases, some temperatures in the living room reach flashover temperatures (approximately
600 °C (1110 °F)) in at least some portion of the room within 180 s after ignition. With the
exception of test 3, the living room temperatures remained at or above 600 °C (1110 °F) until
roof collapse. Temperatures in excess of 600 °C (1110 °F) were seldom sustained in the
bedroom until after apparent ignition of combustibles in the attic area. Combustible materials in
the attic space appeared to ignite 400 s to 450 s after ignition during each test. With the
exception of the first test, roof collapse appears to be preceded by flashover in the attic space.
Even though the noncombustible tile was removed from beneath the fire fighter mannequins’
boots, no temperature changes were measured under the boots until collapse of the roof during
the third and fourth tests. The increased temperatures obtained during the first and second tests
could be the result of burning of portions of the combustible roof structure remote from the
mannequin locations.

Infrared Camera Data

Any substance will emit electromagnetic radiation as a result of electron motion associated with
the internal energy of the material. This internal energy is a strong function of the temperature of
the substance [15]. The emitted radiant energy can range from radio waves to cosmic rays. This
radiant energy is always present, however, the human body can detect only a relatively small
portion of it. Radiation that is detectable as heat or light is referred to as thermal radiation and
occupies a wavelength range of 0.4 um to 1000 um.

The portion of this spectrum visible to the human eye is extremely small, ranging from 0.4 um to
approximately 0.7 um. The color blue is in the range from 0.4 jum to 0.5 ym, the color green is
in the range from 0.5 ,1m to 0.6 1m, and the color red is in the range from 0.6 tum to 0.7 um.

The infrared region of the spectrum is from 0.7 j1m to 1000 um. The infrared region of the
spectrum is divided into three parts: near infrared, mid infrared, and thermal infrared. Only the
thermal infrared portion, 3 um to 1000 um, is related to the sensation of heat. Infrared
measurement devices typically operate somewhere in the range from 3 jum to approximately

30 um.

Infrared thermometers have been in commercial use since the early 1960’s. These electronic

sensors capture the invisible infrared energy naturally emitted from all objects, in proportion to

their temperature and material characteristics. The term emissivity is used to quantify the energy

emitting characteristics of different materials. Most infrared temperature measuring devices

include a user-adjustable emissivity to allow accurate measurement of different materials. An

infrared camera or thermal imager package includes one or more lens, spectral filter detector,
-ll-


wo 22-2 2--------------------- NIST/BERL/MPG --------------------------------
C:\CONE171\RAWDATA\010731A3.CDT

Test Date : 31-Jul-01 Test Time : 01:18 p.m. Operator : Michael Smith

Test Scans
Test Length

228 scans, 3 secs/scan
562.94 secs

Sample Surface Area : 0.01000 m2
Radiant Heat Flux : 35.0 kW/m2
Sample Orientation : Horizontal
Measured Exh. Flow : 0.024 m3/sec
Orifice Plate : 57 mm
Sample Material :

External Oriented Strandboard

SAMP.3

Pre-test Comments:

Samp.in double density alumn.pan edge control.
Thermal absorber applied.
Samp.wt.=74.2g,Samp.t+tpan wt.=77.4g.

Post-test Comments:
Samp.exhibited a uniform combustion process
without any thermal anomalies to report.

aaa Reduction Parameters ---W--~-------- 9-993 -2n2nnnnnnnnnnnnnnnnnnn

C-Factor (Methane) : 0.04381603
Conversion Factor : 13.100 MJ/kg 02
Baseline 02 Reading : 20.981 3
Baseline C02 Reading : 0.05175 %
Baseline CO Reading : 0.00010 %

Sanaa” Test Results -------9--9 9-92 n nnn nnn nnn nnn nn nnn nnn nnn nnn

246.64 kW/m2 at 433.00 secs
155.26 kW/m2
174.22 kW/m2
158.42 kW/m2
141.60 kW/m2
81.99 MJ/m2
13.63 MJ/kg

Peak Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Total Heat Released
Average Effective HOC

Average Specific Ext Area : 69.57 m2/kg
Average Mass Loss Rate: H 12.240 g/s*m2
Entered Initial Specimen Mass : 77.40 g
Measured Final Specimen Mass : 17.24 9g
Average CO Yield : 0.00211 kg/kg
Average C02 Yield : 1.46153 kg/kg
Time to sustained Ignition H 38.11 secs

-70-


1200

1000
800

S

©

5

3 600

Oo

Qa

E

Oo

£
400
200

0 1 1

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Figure 36. Graph showing temperatures measured in the living room during the third test
(distances measured from ceiling downward).

-55-


Additive Method (CAM) procedures presented in his report, the fire resistance rating of a wood
roof assembly consisting of wood trusses, spaced 0.6 m (24 in) on center and protected by a
12.7 mm (// in) thick layer of gypsum board would be at least 20 min. The CAM procedures
assume the gypsum board is continuous, unlike the Phoenix fire tests where an attic access hole
was located directly above the couch.

The fire resistance and ability of a structural member to maintain its load during an actual fire are
influenced by a number of factors. Many of these factors can vary significantly depending on
the specific fire scenario. Fire resistance ratings and measured or predicted times to failure or
collapse should not be relied upon as absolute indicators of time available for operating on or
within a burning structure. Each structure must be evaluated and reevaluated during the fire to
determine whether or not it is safe for fire fighters to remain within any potential collapse zone.

Experimental Configuration

The Phoenix Fire Department built four single story wood frame residential type structures for
this series of tests. These structures were identical except for the roof construction. One
structure had a roof consisting of asphalt shingles on 12.7 mm (4 in) five-ply plywood while a
second structure had asphalt shingles on 12.7 mm ('4 in) oriented strand board (OSB). Both
structures had a layer of 6.8 kg (15 Ib) felt paper between the asphalt shingles and the plywood
or OSB. The other two structures used tile over either plywood or OSB as the roof construction.
The cementatious tile roofs had two layers of 13.6 kg (30 Ib) felt over the plywood or OSB and
nominally 25.4 mm (1 in) by 50.8 mm (2 in) boards to hold the tile in place. The measurements
for the materials used to construct the test structures described in this report are approximate
nominal dimensions.

Each structure consisted of two rooms and an attic space. The rooms were separated by a wall
constructed of 2 x 4 wood studs with a layer of 12.7 mm (% in) gypsum board nailed to each
side. There was a doorway, 0.8 m (2.9 ft) wide and 2 m (6.5 ft) high, in the wall between the two
rooms with its centerline located 4.5 m (14.9 ft) from one exterior wall and 0.7 m (2.4 ft) from
the other exterior wall. Figure | is a photograph of the front of one of the structures, and

Figure 2 provides a rear view. A typical structure is shown in plan view in Figure 3. The
placement of the measurement instruments and dimensions of the structure are shown in Figure
4.

The exterior walls of the structures were composed of 2 x 4 wood studs on 0.4 m (1.3 ft) centers
nailed to a single sole plate and a double top plate. The exterior surfaces of the walls were
covered with 15.9 mm (5/8 in) T-1-11 wood siding using galvanized nails. Interior walls and
ceilings had 12.7 mm (‘4 in) gypsum board nailed to the studs. All of the joints between boards
were taped, and the taped joints and nails were covered with joint compound. In addition, the
four walls in the back room (bedroom) and the two walls in the front room (living room) were
covered with 3.2 mm (1/8 in) pressboard paneling attached using construction adhesive and
small brads.

-3-


Figure 7. Photograph of “living room” area showing furniture arrangement.

-26-


1200

1000
800

S

©

5

3 600

Oo

Qa

E

Oo

£
400
200

0 1

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Figure 43. Graph showing temperatures measured in the north portion of the attic during the
fourth test (distances measured from roof peak downward).

-62-


1200

1000

Standing - Left
S— Standing - Right
© — Leaning - Left
- -x-- Leaning - Right

800
S
©
5

3 600
Oo
Qa
E
Oo
£

400

200

0

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Figure 45. Graph showing temperatures measured on the roof under the fire fighter mannequins’
boots during the fourth test.

-64-


Figure 46. Test 3 shown a few seconds after ignition (top — normal video, middle — fire
department thermal imager, bottom — high end, quantitative infrared camera)

- 65-


K 5.28 7

l 0.86 >}

AN ———
Window
“ 1.6
Opening w/ Thermocouple
Slide Array
1.17 ef 3.45
2.6 >
a
0.28
61 FS : hina
K 0.89 |
pe a> N -
Opening w/ |
Ly Slide Opening w/ L 7
‘ Slide :
Thermocouple |

4.22 0.89 |
3.28 =

7

Figure 4, Plan view of generic structure showing locations of measurement instruments and
dimensions (all dimensions in m).

-23-


wo 22-2 2--------------------- NIST/BFRL/MPG --------------------------------
C:\CONE171\RAWDATA\010731A8.CDT

Test Date : 31-Jul-01 Test Time : 03:01 p.m. Operator : Michael Smith

Test Scans 171 scans, 3 secs/scan

Test Length : 393.92 secs
Sample Surface Area : 0.01000 m2
Radiant Heat Flux > 70.0 kW/m2
Sample Orientation : Horizontal
Measured Exh. Flow : 0.024 m3/sec
Orifice Plate : 57 mm
Sample Material :

External Oriented Strandboard

SAMP.2

Pre-test Comments:

Samp.in double density alumn.pan edge control.
Thermal absorber applied.
Samp.wt.=74.3g,Samp.t+pan wt.=77.5g.

Post-test Comments:
Samp.exhibited a uniform combustion process
without any thermal anomalies to report.

aaa Reduction Parameters ---W--~-------- 9-993 -2n2nnnnnnnnnnnnnnnnnnn

C-Factor (Methane) : 0.04381603
Conversion Factor : 13.100 MJ/kg 02
Baseline 02 Reading : 20.986 3%
Baseline C02 Reading : 0.04789 %
Baseline CO Reading : 0.00009 %

Sanaa” Test Results -------9--9 9-92 n nnn nnn nnn nnn nn nnn nnn nnn nnn

332.89 kW/m2 at 34.00 secs
225.25 kW/m2
271.41 kW/m2
234.63 kW/m2
236.61 kW/m2
86.51 MJ/m2
14.20 MJ/kg

Peak Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Total Heat Released
Average Effective HOC

Average Specific Ext Area : 124.59 m2/kg
Average Mass Loss Rate: H 17.007 g/s*m2
Entered Initial Specimen Mass : 77.50 g
Measured Final Specimen Mass : 16.57 g
Average CO Yield : 0.00407 kg/kg
Average C02 Yield : 1.50906 kg/kg
Time to sustained Ignition H 10.03 secs

-75-


List of Tables

Page

Table 1. Fuel Load .
Table 2. Summary of Cone Calorimeter Data
Table 3. Uncertainty in Experimental Data ...

14

-Vi-


Figure 27.
Figure 28.
Figure 29.
Figure 30.
Figure 31.
Figure 32.
Figure 33.
Figure 34.

Figure 35.

Figure 36

Figure 37.
Figure 38.
Figure 39.
Figure 40.
Figure 41.
Figure 42.
Figure 43.
Figure 44.
Figure 45.
Figure 46.

Figure 47.

Graph showing temperatures measured in the bedroom during the first test

(distances measured from ceiling downward) ..........:cseesesesseeseeeeeseeeeseeeeeeneeeeee 46
Graph showing temperatures measured in the north portion of the attic

during the first test (distances measured from roof peak downward)..............0+ 47
Graph showing temperatures measured in the south portion of the attic

during the first test (distances measured from roof peak downward)...........00 48
Graph showing temperatures measured on the roof under the fire fighter
mannequins’ boots during the first test... tesesesseseseseseseeseseeseseseeneseeneneereneaee 49
Graph showing temperatures measured in the living room during the

second test (distances measured from ceiling downward)...........scsseseeeeeeeeees 50
Graph showing temperatures measured in the bedroom during the second

test (distances measured from ceiling downwatd)...........ccsecsesesesesesseseseeeeeereneeee 51
Graph showing temperatures measured in the north portion of the attic

during the second test (distances measured from roof peak downward).............. 52

Graph showing temperatures measured in the south portion of the attic
during the second test (distances measured from roof peak downward)
Graph showing temperatures measured on the roof under the fire fighter
mannequins’ boots during the second test
Graph showing temperatures measured in the living room during the third

test (distances measured from ceiling downwatd)............csesseseseeesesreseseereneeteneees 55
Graph showing temperatures measured in the bedroom during the third
test (distances measured from ceiling downward)..........ccesseseesesesseeeeeeeeeeeneees 56

Graph showing temperatures measured in the north portion of the attic
during the third test (distances measured from roof peak downward).
Graph showing temperatures measured in the south portion of the attic

during the third test (distances measured from roof peak downward).............06 58
Graph showing temperatures measured on the roof under the fire fighter
mannequins’ boots during the third test... eeseeeseeeseeeeeeeeeetseteseteeeneees 59
Graph showing temperatures measured in the living room during the

fourth test (distances measured from ceiling downward) ..........csseeeeeseneeeeeees 60
Graph showing temperatures measured in the bedroom during the fourth

test (distances measured from ceiling downward)............cccccseseeseeeeseeeeeeeees 61
Graph showing temperatures measured in the north portion of the attic

during the fourth test (distances measured from roof peak downward) ............... 62
Graph showing temperatures measured in the south portion of the attic

during the fourth test (distances measured from roof peak downward) ............... 63

Graph showing temperatures measured on the roof under the fire fighter
mannequins’ boots during the fourth test.
Test 3 shown a few seconds after ignition (top — normal video, middle —
Infrared Camera A, bottom — Infrared Camera B)....
Test 3 shown approximately 10 s before collapse of the roof structure (top

—normal video, middle Infrared Camera A, bottom — Infrared Camera B)......... 66



processing electronics, and a housing to hold the components together and protect them from the
environments. Some infrared imaging cameras measure temperature contours across a surface in
front of the lens using scanning optics; other cameras use staring arrays to determine temperature
contours. The total energy reaching the sensor is the sum of (1) energy emitted from the target,
in proportion to temperature and emissivity; (2) energy reflected from the target, in proportion to
its reflectivity or the presence of any hot objects nearby; and (3) energy transmitted through the
target, in proportion to its transmissivity and the presence of any hot objects behind it.
Emissivity and transmissivity are wavelength dependent properties for many materials.

Many factors enter into the considerations of the best camera waveband selection. The
theoretical implications of operating in a particular waveband and the performance factors of the
camera must be considered. Most infrared cameras are filtered to operate in the 3 ym to 5 um
and 8 jm to 14 um waveband regions. These two operating regions are directly related to
atmospheric propagation properties. If a wide range of applications is being considered, the 7 to
14 um region would be preferred. However, more energy is available for detectors in the 3 to

5 um region when the sources are very hot, 500 °C (930 °F) to 1000 °C (1830 °F).

During each fire test, two infrared cameras and one standard video camera were used to record
similar views. Camera A, which was typical of what fire fighters might employ, utilizes focal
plane array technology and is capable of detecting infrared radiation in the 8 to 14 jum range.
Camera B, which is often used for research applications, operates using focal plane array
technology and detects radiation in the waveband 3.4 to 5 um. Camera B offers the user the
ability to calibrate the focal plane array sensor, adjust the target emissivity, and achieve better
temperature resolution by employing narrower temperature ranges. Camera B is capable of
displaying quantitative temperature information, but also costs between three and five times
more than Camera A. Figure 46 presents the same view from the three cameras a few seconds
after ignition during test 3. The scene shown in Figure 47 is test 3 approximately 10 s prior to
collapse of the roof structure. In both figures, the top image is from the standard video camera,
the middle image is from Camera A, and the bottom image is from Camera B.

During these tests, the standard video camera documented that the roof began to sag or drop
slightly just before failing completely. The time between the first appearance of a noticeable
depression on the roof and the complete collapse of the roof appeared too short to allow any
personnel on the roof to escape safely. The thermal images provided by the infrared cameras
were also examined for evidence of an imminent collapse. The thermal images did not provide
any warning of the roof collapse. The thermal radiation from the smoke plumes on both ends of
the roof was radiated back to the surface of the roof. This reradiated energy appeared to wash
out any thermal signature of the energy being conducted through the roof. Another factor that
could make it difficult to see via thermal imager the energy being conducted through the roof
would be the presence of water on the shingles or tiles. During one of the experiments, the fire
department attempted to cool the boom of the extraction crane and the wind carried some of the
water droplets onto one side of the roof. The temperature of the roof appeared to decrease, and
the temperature difference across the wetted portion of the roof disappeared. The presence of hot
smoke plumes or water from suppression activity or rain make it very difficult to see the thermal

-12-


died as a result of being caught or trapped and 26 fire fighters were struck and killed by debris
from the collapse. In a 2002 report [5], Dr. Fahy of NFPA indicates that the rate of deaths due to
heart attacks at structural fire is decreasing while the rate of deaths due to traumatic injuries is
increasing. Structural collapse is identified as one of the major causes of these traumatic injuries.
A recent National Institute of Standards and Technology (NIST) report [6] indicates that deaths
resulting from structural collapse have decreased overall during the last 23 years. However, the
percentage of those deaths occurring at residential fires has been increasing.

As part of a project funded by the United States Fire Administration, the Building and Fire
Research Laboratory (BFRL) at NIST is exploring the feasibility of developing a system for use
by fire fighters to predict structural collapse during fire ground operations. Predicting a potential
structural collapse is one of the most challenging tasks facing an incident commander at a fire
scene. Usually the lack of information on the construction of the building, fire size, fire location,
fire burn time, condition of the building, fuel load, etc., makes the task nearly impossible.

The fire department in the City of Phoenix, Arizona conducted a series of live fire training
exercises in various structures in an effort to better educate fire fighters about structural collapse.
While some of the structures in this ongoing series of training exercises were scheduled for
demolition [7], other structures such as those described in this report were built specifically for
the fire tests. Each structure was allowed to burn until some portion of the structure collapsed.
In collaboration with the Phoenix Fire Department, researchers from NIST provided
measurement support during the fire tests. Using video and data obtained from two different fire
test series, the fire department developed a set of three videotapes dealing with fire ground
command and collapse issues [8].

This report presents the results obtained from a set of tests that were conducted in single story
wood frame residential structures. These structures were constructed for test experiments in
order to examine several issues related to fire fighter health and safety. The first goal of the tests
was to obtain temperature data from a burning structure during a collapse. Second, various
techniques and tools were being evaluated for use in predicting structural collapse. Specifically,
the use of thermal imaging techniques was being examined as a means to predict collapse. In
addition, the exterior of the building was observed prior to and during collapse to identify any
visual indicators of impending collapse. Subsequent reports will provide additional analysis of
these fires and will also assess the effectiveness of various methodologies for predicting the
onset of structural collapse.

These tests were not designed to evaluate the fire endurance of wood trusses, gypsum wallboard,
wood studs, or any other structural elements used in the construction of the four structures. The
fire scenario used in this study was designed to reach flashover conditions rapidly to force a
partial or complete collapse of the structure. Many factors influence the failure of structural
elements including the load on the element, protection of the element, fire intensity, and fire
duration. More or less time may be available before failure of the element depending on the
particular fire scenario. Kenneth E. Bland provides a review of and expert procedure for
predicting the failure of wood assemblies when exposed to fire [9]. Using the Component

-2-


wo 22-2 2--------------------- NIST/BFRL/MPG --------------------------------
C:\CONE171\RAWDATA\010731B1.CDT

Test Date : 31-Jul-01 Test Time : 03:34 p.m. Operator : Michael Smith

Test Scans 159 scans, 3 secs/scan

Test Length : 355.86 secs
Sample Surface Area : 0.01000 m2
Radiant Heat Flux > 70.0 kW/m2
Sample Orientation : Horizontal
Measured Exh. Flow : 0.024 m3/sec
Orifice Plate : 57 mm

Sample Material
External 5 PLY Plywood
SAMP.1

Pre-test Comments:

Samp.in double density alumn.pan edge control.
Thermal absorber applied.
Samp.wt.=58.0g,Samp.t+pan wt.=60.9g.

Post-test Comments:
Samp.exhibited a uniform combustion process
without any thermal anomalies to report.

aaa Reduction Parameters ---W--~-------- 9-993 -2n2nnnnnnnnnnnnnnnnnnn

C-Factor (Methane) : 0.04381603
Conversion Factor : 13.100 MJ/kg 02
Baseline 02 Reading : 20.986 3%
Baseline C02 Reading : 0.04953 %
Baseline CO Reading : 0.00008 %

Sanaa” Test Results -------9--9 9-92 n nnn nnn nnn nnn nn nnn nnn nnn nnn

257.48 kW/m2 at 49.00 secs
167.08 kW/m2
174.59 kW/m2
159.94 kW/m2
178.10 kW/m2
59.15 MdJ/m2
13.04 MJ/kg

Peak Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Total Heat Released
Average Effective HOC

Average Specific Ext Area : 105.84 m2/kg
Average Mass Loss Rate: H 14.742 g/s*m2
Entered Initial Specimen Mass : 60.90 g
Measured Final Specimen Mass : 15.54 g
Average CO Yield : 0.00235 kg/kg
Average C02 Yield : 1.37760 kg/kg
Time to sustained Ignition H 6.73 secs

-77-


B]
[4]
[5]
[6]

[7]

[8]
19]

[10]

(11
[12]

[13]

[14]

[15]

[16]

(17]

[18]

“Fire Fighter Deaths in Structural Collapses, 1979-1988,” National Fire Protection
Association, Quincy, MA, August 1989.

“Fire Ground Fatalities as a Result of Structural Collapse, 1983-1992,” National Fire
Protection Association, Quincy, MA, August 1993.

Fahy, R.F., “U.S. Fire Service Fatalities in Structure Fires, 1977-2000,” National Fire
Protection Association, Quincy, MA, July 2002.

Brassell, L.D. and Evans, D.D., “Trends in Firefighter Fatalities Due to Structural
Collapse, 1979-2002,” NISTIR 7069, National Institute of Standards and Technology,
Gaithersburg, MD, November 2003.

Stroup, D.W., Madrzykowski, D., Walton, W.D., and Twilley, W., “Structural Collapse
Fire Tests: Single Story, Ordinary Construction Warehouse,” NISTIR 6959, National
Institute of Standards and Technology, Gaithersburg, MD, May 2003.

Brunacini, A., “Critical Fireground Factors Video Set,” VCRSET1, National Fire
Protection Association, Quincy, MA, 2002.

Bland, K.E., “Behavior of Wood Exposed to Fire: A Review and Expert Judgment
Procedure for Predicting Assembly Failure,” Master’s Thesis, Worcester Polytechnic
Institute, Worcester, MA, May 1994.

Babrauskas, V., “Development of the Cone Calorimeter — A Bench-Scale Heat Release
Rate Apparatus Based on Oxygen Consumption,” Journal of Fire and Materials, Vo/. 8,
pp. 81-95, 1984.

Janssens, M., “Section 3/Chapter 2: Calorimetery,” The SFPE Handbook of Fire
Protection Engineering, gn ed., SFPE, Bethesda, MD, pp. 3-16 — 3-36, 1995.

“ASTM E 1354: Test Method for Heat and Visible Smoke Release Rates for Materials
and Products Using an Oxygen Consumption Calorimeter,” ASTM Fire Test Standards,
4" ed., ASTM, Philadelphia, PA, pp. 968-984, 1993.

“ISO 5660-1: Rate of Heat Release of Building Products (Cone Calorimeter),”
International Organization for Standardization, Geneva, Switzerland, 1992.

Parker, W., “Calculations of the Heat Release Rate by Oxygen Consumption for Various
Applications,” NBSIR 81-2427, National Bureau of Standards, Gaithersburg, MD, March
1982.

Siegel, R. and Howell, J.R., Thermal Radiation Heat Transfer, 2" edition, McGraw-Hill
Book Company, New York, NY, pg. 1, 1981.

Babrauskas, V., “Specimen Heat Fluxes for Bench-Scale Heat Release Rate Testing,”
Fire and Materials, Interflam °93, Fire Safety, International Interflam Conference, 6",
March 30-April 1, 1993, Oxford, England, Interscience Communications Ltd., London,
England, pp. 57-74, 1993.

Madrzykowski, D., “Office Work Station Heat Release Rate Study: Full Scale vs. Bench
Scale,” Interflam ’96, International Interflam Conference, 7th Proceedings, March 26-28,
1996, Cambridge, England, Interscience Communications, Ltd., London, England, pp.
47-55, 1996.

Taylor, B.N. and Kuyatt, C.E., “Guidelines for Evaluating and Expressing the
Uncertainty of NIST Measurement Results,” NIST TN 1297, National Institute of
Standards and Technology, Gaithersburg, MD, January 1994.

-18-


NISTIR 7094

Structural Collapse Fire Tests:
Single Story, Wood Frame Structures

David W. Stroup
Nelson P. Bryner
Jack Lee

Jay McElroy

Gary Roadarmel
William H. Twilley

EES.
RSA FEMA

@ ;

oS oe y
Sponsored in part by
Department of Homeland Security

Federal Emergency Management Agency
United States Fire Administration

NUsT

National Institute of Standards and Technology
Technology Administration, U.S. Department of Commerce



Figure 22. Photograph of test structure at 960 s after ignition with portion of roof structure
burning.

-41-


Table 1. Fuel Load

Test No. 1 Test No. 2 Test No. 3 Test No. 4
Item Weight Weight Weight Weight
kg (Ib kg (Ib kg (Ib kg (Ib
Bedroom
Chair 34 (75) 32.7 (72) 30.8 (68) 34.5 (76)
Dresser | 50.8 (112) 45.3 (100) 49 (108) 47.6 (105)
Bed Stand 1 13.6 (30) 13.6 (30) 13.6 (30) 13.6 (30)
Lamp 1 4.5 (10) 3.6 (8) 2.7 (6) 2.3 (5)
Bed 1 64.9 (143) 63.5 (140) 64 (141) 64.4 (142)
Bed Stand 2 9.5 (21) 14 (31) 13.6 (30) 13.6 (30)
Lamp 2 4(9) 2.3 (5) 2.7 (6) 3.2 (7)
Bed 2 69.9 (154) 62.6 (138) 63.5 (140) 65.8 (145)
Dresser 2 50.3 (11 45.3 (100 50.8 (112 49.4 (109
Living Room
Chair 1 35.4 (78) 36.3 (80) 34.5 (76) 35.8 (79)
Table Lamp 1 1.8 (4) 4.5 (10) 3.6 (8) 3.2 (7)
End Table | 14 G1) 13.6 (30) 13.6 (30) 14 (31)
Sofa 97.5 (215) 98.9 (218) 87.5 (193) 95.3 (210)
Table Lamp 2 2.3 (5) 4.5 (10) 2.7 (6) 3.2(7)
End Table 2 13.6 (30) 13.6 (30) 13.6 (30) 13.6 (30)
Chair 2 33.6 (74) 33.6 (74) 30.4 (67) 32.7 (72)
Coffee Table 19.1 (42) 20 (44) 21.8 (48) 20.4 (45)
Love Seat 51.7 (114) 51.7 (114) 51.3 (113) 50.8 (112)

Four thermocouple arrays were positioned in each structure to obtain temperature data during the
fire test. The first array was located in the living room 0.8 m (2.6 ft) from the front wall and

0.8 m (2.6 ft) from the adjacent wall. The second thermocouple array was placed in the rear
room between the two beds, 1.6 m (5.3 ft) from the rear wall and 2.6 m (8.6 ft) from the north
wall. These arrays had Chromel-Alumel (Type K)! thermocouples located at 25 mm (1 in),

0.3 m(1 ft), 0.6 m (2 ft), 0.9 m (3 ft), 1.2m (4 ft), 1.5 m (5 ft), 1.8 m (6 ft), and 2.1 m (7 ft)
below the ceiling. Two thermocouple arrays were located in the attic space along the attic

centerline that ran parallel to the front wall of each structure. These arrays were located 0.8 m
(2.6 ft) from either gabled end of each structure. The attic arrays had thermocouples located at
25 mm (1 in), 0.2 m (0.5 ft), 0.3 m (1 ft), 0.5 m (1.5 ft), 0.6 m (2 ft), 0.8 m (2.5 ft), 0.9 m (3 ft),
and 1.1 m (3.5 ft) below the attic peak (Figure 11).

' Certain commercial equipment, instruments, or materials are identified in this paper to foster understanding. Such
identification does not imply recommendation or endorsement by the National Institute of Standards and
Technology, nor does it imply that the materials or equipment identified are necessarily the best available for the
purpose.

-5-


The front wall of the living room had a doorway, approximately 0.9 m (2.9 ft) wide and 2 m

(6.7 ft) high, located with its centerline 0.6 m (1.9 ft) from one wall and 4.2 m (14.8 ft) from the
opposite wall. A hollow core wood door was mounted in the doorway opening. In the living
room of each structure, the walls adjacent to the front wall each had an approximately 1.2 m

(4 ft) wide by 0.9 m (3ft) high section removed to let air into the room. One wall in the bedroom
had a 1.2 m (4 ft) wide by 0.9 m (3 ft) high section removed, and the rear wall had a 0.9 m (3 ft)
by 0.9 m (3 ft) window with glass. Each of the three cutout sections of wall had a piece of
plywood on a slide track allowing it to be moved back and forth to regulate the flow of air into
the room.

The roof system was built with manufactured trusses on 0.6 m (2 ft) centers (Figure 5). The
gable ends were studded with 51 mm (2 in) by 76 mm (3 in) lumber and covered with 12.7 mm
(% in) high density fiberboard. The trusses were nailed on each end and attached to the top plate
with metal hurricane ties. All structures had 2 x 6 boards nailed to the truss tails and the tails on
the trusses were cut off at 0.5 m (1.7 ft). The outside rafts were nailed to 2 x 4 boards and
attached to the second truss at 1.2 m (4 ft) intervals.

A 1.5 m (5 ft) long base cabinet made of particle board and a counter top were placed along the
front wall of the living room. A second 1.5 m (5 ft) long cabinet was nailed to the wall above the
first cabinet. Electrical outlet boxes were installed in the walls at various locations throughout
the two rooms. A 0.3 m (0.8 ft) by 0.3 m (0.8 ft) hole was cut in the center of the ceiling in the
living room and covered with a plastic grill to simulate a vent. The location of this vent was
selected to facilitate fire spread into the attic space. A 0.6 m (2 ft) by 0.8 m (2.5 ft) hole was cut
in the ceiling of the living room to allow access to the attic space. This opening was covered
with a 12.7 mm (4 in) piece of drywall held in place using wood molding strips (Figure 6).

Identical pieces of furniture, typical of a residential occupancy, were placed in each of the four
structures. The living room contained a couch, a love seat, and two chairs consisting of wood
frames with polyurethane foam cushioning material. Two wood end tables, a wood coffee table,
and two table lamps were also placed in the living room (Figures 7 and 8). The bedroom
contained two sets of foam mattresses and box springs on metal frames. Wood bed tables were
placed adjacent to each bed. Two wood dressers were located in the room. One dresser was
located along the wall opposite the ends of the two beds while the second dresser was adjacent to
the side of the second bed. Finally, a chair with polyurethane padding on a wood frame was
positioned in the bedroom diagonally opposite the end corner of the first bed (Figures 9 and 10).
Table lamps were placed on top of the two bed tables. The mass of each object in the two rooms
for all four tests is summarized in Table 1. Both rooms in each structure had nylon wall-to-wall
carpet laid on the floor over 1.4 kg (3 Ib) pad.


1200

O-~ Standing - Left

1000 &— Standing - Right
© Leaning - Left

- -*-- Leaning - Right

800
S
g
>
3 600
Oo
Qa
E
Oo f
£

400

200

800 1000 1200 1400 1600

Time (s)

Figure 35. Graph showing temperatures measured on the roof under the fire fighter mannequins’
boots during the second test.

-54-


Figure 18. Photograph of test structure at 210 s after ignition.

-37-


wo 22-2 2--------------------- NIST/BFRL/MPG --------------------------------
C:\CONE171\RAWDATA\010731B2.CDT

Test Date : 31-Jul-01 Test Time : 03:51 p.m. Operator : Michael Smith

Test Scans 169 scans, 3 secs/scan

Test Length : 387.58 secs
Sample Surface Area : 0.01000 m2
Radiant Heat Flux  : 70.0 kW/m2
Sample Orientation : Horizontal
Measured Exh. Flow : 0.024 m3/sec
Orifice Plate : 57 mm

Sample Material
External 5 PLY Plywood
SAMP .2

Pre-test Comments:

Samp.in double density alumn.pan edge control.
Thermal absorber applied.
Samp.wt.=60.3g,Samp.t+pan wt.=63.2g.

Post-test Comments:
Samp.exhibited a uniform combustion process
without any thermal anomalies to report.

aaa Reduction Parameters ---W--~-------- 9-993 -2n2nnnnnnnnnnnnnnnnnnn

C-Factor (Methane) : 0.04381603
Conversion Factor : 13.100 MJ/kg 02
Baseline 02 Reading : 20.987 3
Baseline C02 Reading : 0.04982 %
Baseline CO Reading : 0.00009 %

Sanaa” Test Results -------9--9 9-92 n nnn nnn nnn nnn nn nnn nnn nnn nnn

262.58 kW/m2 at 25.00 secs
169.23 kW/m2
169.96 kW/m2
149.30 kW/m2
176.07 kW/m2
64.48 MJ/m2
13.56 MJ/kg

Peak Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Total Heat Released
Average Effective HOC

Average Specific Ext Area : 141.90 m2/kg
Average Mass Loss Rate: H 13.859 g/s*m2
Entered Initial Specimen Mass : 63.20 g
Measured Final Specimen Mass : 15.66 g
Average CO Yield : 0.00335 kg/kg
Average C02 Yield : 1.41203 kg/kg
Time to sustained Ignition H 9.76 secs

- 78 -


Figure 6. Photograph showing “living room” ceiling with ceiling louvers, electrical boxes, and
attic access.

-25-


Figure 23. Photograph of test structure at 1010 s after ignition as collapse is starting.

-42-


Figure 5. Diagram showing typical construction of the structure.

-24-


1200
1000
&
ial
7
800 |
is)
2
>
8 600
oO
Qa
E
oO
2
400
200
0 c “ Ll Ll

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Figure 42. Graph showing temperatures measured in the bedroom during the fourth test
(distances measured from ceiling downward).

-61-


Structural Collapse Fire Tests:
Single Story Wood Frame Structures

David W. Stroup, Nelson P. Bryner, Jack Lee,
Jay McElroy, Gary Roadarmel, and William H. Twilley

Abstract

A series of fire tests was conducted in Phoenix, Arizona to collect data for a project examining
the feasibility of predicting structural collapse. The fire test scenario was selected as part of a
training video being prepared by the Phoenix, Arizona Fire Department. Multiple fires were
started in each structure to facilitate collapse; the fires were not intended to test the fire
endurance of the structures. Four structures with different roof constructions were used for the
fire tests. Temperatures were measured as a function of time in four locations within each
structure. Furniture items were placed in the front and back of each structure to simulate living
room and bedroom areas. The living room and bedroom areas of each structure were ignited
simultaneously using electric matches. Peak temperatures obtained during the tests ranged from
approximately 800 °C (1500 °F) to 1000 °C (1800 °F). The roof of each structure collapsed
approximately 17 minutes after ignition. In addition to the full scale tests, the plywood and
oriented strand board (OSB) roofing materials were tested using a cone calorimeter to
characterize the fire properties of the materials.

Key Words:
building collapse; building fires; fire data; fire fighting; large scale fire tests; structural failure;
temperature measurements

Introduction

Every year, approximately 100 fire fighters die in the line of duty, and 90,000 to 100,000 are
injured [1]. In 1999, the United States Fire Administration estimated that slightly more than

30 % of the fire fighter fatalities occurring on the fire ground resulted from something other than
stress and heart attacks [2]. Stress and heart attacks, accounting for almost half of the fire fighter
fatalities, remain the leading cause of death. The categorization of the statistics does not lend
itself to easy identification of those deaths that occurred due to structural issues including failure
and collapse. Examination of specific incidents in 1999 indicates that 18 fire fighters or 16 %
died as a result of being trapped in a structure or involved in a collapse [2]. Based on data
obtained from 1979 through 1988, a report prepared by the National Fire Protection Association
(NFPA) for the Federal Emergency Management Agency [3] indicates that 93 of the 474 fire
fighters who were killed at structure fires died as a result of structural collapse. Of these, 60 %
were caught or trapped in the collapse while 40 % were struck by collapsing walls or sections of
walls. A subsequent report examined 1150 fire fighter fatalities that occurred during the period
from 1983 through 1992 [4]. Of the 390 deaths that occurred at structure fires, 45 fire fighters

-1-


Multiplying the combined standard uncertainty by a coverage factor of two results in the
expanded uncertainty which corresponds to a 95 percent confidence interval (20).

Components of uncertainty are tabulated in Table 3. Some of these components, such as the zero
and calibration elements, are derived from instrument specifications, while other components,
such as positioning include past experience. The combined standard uncertainty for gas
temperature includes a component that is related to the position of the thermocouple. Each
thermocouple array was carefully installed and positioned as each structure was prepared for
each experimental burn. Each thermocouple was tested individually for proper response to flame
temperatures. The position of each thermocouple was rechecked during the final steps prior to
ignition. Several load cells were utilized to measure fuel package mass. Each load cell was
calibrated with a standard mass prior to recording the mass of each fuel item. All fuel items,
such as bed, dresser, or sofa, in a particular structure were weighed, then items were selected at
random to be reweighed a second time in order to help estimate repeatability.

The combined standard uncertainty for infrared camera temperatures includes components
related to the calibration of the thermal camera which were estimated from manufacturer
specifications. Other uncertainty components including material emissivity and surface
properties were estimated based on prior experience. Uncertainty components for the cone
calorimeter were estimated based on manufacturer specifications and past experience using the
cone calorimeter to collect ignition and flammability properties. Uncertainties associated with
oxygen calorimetry techniques is discussed in greater detail by Babrabrauskas et al [19] and
Bryant et al. [20]

Table 3. Uncertainty in Experimental Data

Component Combined Total
Standard Standard Expanded
Uncertainty Uncertainty Uncertainty
Gas Temperature
Zero £2%
Calibration +2%
Position +5% + 12% = 25%
Repeatability +5%
Random +10%
Mass of Fuel Package
Zero +2%
Calibration +7% £9% +18%
Repeatability +5%
Random +3%

-15-


wo 22-2 2--------------------- NIST/BERL/MPG --------------------------------
C:\CONE171\RAWDATA\010731B3.CDT

Test Date : 31-Jul-01 Test Time : 04:04 p.m. Operator : Michael Smith

Test Scans
Test Length

179 scans, 3 secs/scan
417.46 secs

Sample Surface Area : 0.01000 m2
Radiant Heat Flux  : 70.0 kW/m2
Sample Orientation : Horizontal
Measured Exh. Flow : 0.024 m3/sec
Orifice Plate : 57 mm

Sample Material
External 5 PLY Plywood
SAMP.3

Pre-test Comments:

Samp.in double density alumn.pan edge control.
Thermal absorber applied.
Samp.wt.=65.0g,Samp.t+pan wt.=67.8g.

Post-test Comments:
Samp.exhibited a uniform combustion process
without any thermal anomalies to report.

aaa Reduction Parameters ---W--~-------- 9-993 -2n2nnnnnnnnnnnnnnnnnnn

C-Factor (Methane) : 0.04381603
Conversion Factor : 13.100 MJ/kg 02
Baseline 02 Reading : 20.988 %
Baseline C02 Reading : 0.05011 %
Baseline CO Reading : 0.00009 %

Sanaa” Test Results -------9--9 9-92 n nnn nnn nnn nnn nn nnn nnn nnn nnn

240.95 kW/m2 at 22.00 secs
168.73 kW/m2
147.92 kW/m2
161.98 kW/m2
185.50 kW/m2
69.85 MJ/m2
13.73 MJ/kg

Peak Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Total Heat Released
Average Effective HOC

Average Specific Ext Area : 143.74 m2/kg
Average Mass Loss Rate: H 14.741 g/s*m2
Entered Initial Specimen Mass : 67.80 g
Measured Final Specimen Mass : 16.91 g
Average CO Yield : 0.00461 kg/kg
Average C02 Yield : 1.39783 kg/kg
Time to sustained Ignition H 6.69 secs

-79-


1200

1000
800
i)
2
>
3 600
o
Qa
&
o
2
400
beer \,
200 p \ a wa
Pewee |
_e ~ gp
0 | L

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Figure 33. Graph showing temperatures measured in the north portion of the attic during the
second test (distances measured from roof peak downward).

-52-


wo 22-2 2--------------------- NIST/BFRL/MPG --------------------------------
C:\CONE171\RAWDATA\010731A8.CDT

Test Date : 31-Jul-01 Test Time : 03:15 p.m. Operator : Michael Smith

Test Scans
Test Length

184 scans, 3 secs/scan
432.87 secs

Sample Surface Area : 0.01000 m2
Radiant Heat Flux > 70.0 kW/m2
Sample Orientation : Horizontal
Measured Exh. Flow : 0.024 m3/sec
Orifice Plate : 57 mm
Sample Material :

External Oriented Strandboard

SAMP.3

Pre-test Comments:

Samp.in double density alumn.pan edge control.
Thermal absorber applied.
Samp.wt.=82.2g,Samp.+pan wt.=85.4g.

Post-test Comments:
Samp.exhibited a uniform combustion process
without any thermal anomalies to report.

aaa Reduction Parameters ---W--~-------- 9-993 -2n2nnnnnnnnnnnnnnnnnnn

C-Factor (Methane) : 0.04381603
Conversion Factor : 13.100 MJ/kg 02
Baseline 02 Reading : 20.986 3%
Baseline C02 Reading : 0.04896 %
Baseline CO Reading : 0.00009 %

Sanaa” Test Results -------9--9 9-92 n nnn nnn nnn nnn nn nnn nnn nnn nnn

328.92 kW/m2 at 40.00 secs
225.23 kW/m2
265.81 kW/m2
236.29 kW/m2
231.97 kW/m2
95.28 MJ/m2
14.16 MJ/kg

Peak Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Total Heat Released
Average Effective HOC

Average Specific Ext Area : 129.81 m2/kg
Average Mass Loss Rate: H 17.266 g/s*m2
Entered Initial Specimen Mass : 85.40 g
Measured Final Specimen Mass : 18.12 g
Average CO Yield : 0.00408 kg/kg
Average C02 Yield : 1.49875 kg/kg
Time to sustained Ignition H 11.20 secs

-76-


1200

1000
Standing - Left
Standing - Right }
800 © ~~ Leaning - Left i
oO - --- Leaning - Right
©
5 i
® 600 4
Oo h:
Qa Ae
€ rH
Oo i
F b
400 HH
i
|
[
200 |
0 es REA i f

0 200 400 600 800 1000 1200 1400 1600
Time (s)

Figure 40. Graph showing temperatures measured on the roof under the fire fighter mannequins’
boots during the third test.

-59-


Figure 13. Photograph showing “bedroom” with ignition location in corner of chair under the
newspaper.

-32-


wo 22-2 2--------------------- NIST/BERL/MPG --------------------------------
C:\CONE171\RAWDATA\010731A5.CDT

Test Date : 31-Jul-01 Test Time : 01:54 p.m. Operator : Michael Smith

Test Scans
Test Length

228 scans, 3 secs/scan
562.37 secs

Sample Surface Area : 0.01000 m2
Radiant Heat Flux  : 35.0 kW/m2
Sample Orientation : Horizontal
Measured Exh. Flow : 0.024 m3/sec
Orifice Plate : 57 mm

Sample Material
External 5 PLY Plywood
SAMP .2

Pre-test Comments:

Samp.in double density alumn.pan edge control.
Thermal absorber applied.
Samp.wt.=59.0g,Samp.t+pan wt.=61.9g.

Post-test Comments:
Samp.exhibited a uniform combustion process
without any thermal anomalies to report.

aaa Reduction Parameters ---W--~-------- 9-993 -2n2nnnnnnnnnnnnnnnnnnn

C-Factor (Methane) : 0.04381603
Conversion Factor : 13.100 MJ/kg 02
Baseline 02 Reading : 20.985 %
Baseline C02 Reading : 0.05104 %
Baseline CO Reading : 0.00009 %

Sanaa” Test Results -------9--9 9-92 n nnn nnn nnn nnn nn nnn nnn nnn nnn

201.86 kW/m2 at 430.00 secs
112.72 kW/m2
115.17 kW/m2

Peak Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate T60

Average Heat Release Rate 87.06 kW/m2
Average Heat Release Rate 97.40 kW/m2
Total Heat Released 58.52 MJ/m2

Average Effective HOC 12.82 MJ/kg

Average Specific Ext Area : 59.05 m2/kg
Average Mass Loss Rate: H 9.897 g/s*m2
Entered Initial Specimen Mass : 61.90 g
Measured Final Specimen Mass : 16.21 9g
Average CO Yield : 0.00133 kg/kg
Average C02 Yield : 1.33092 kg/kg
Time to sustained Ignition H 46.32 secs

-72-


Figure 14. Photograph of test structure at 60 s after ignition.

-33-


1200

1000
800
S
2
>
3 600
oO
Qa
a
oO
2
400
200
ot eo

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Figure 29. Graph showing temperatures measured in the south portion of the attic during the
first test (distances measured from roof peak downward).

- 48 -


Figure 2. Photograph showing rear and one side of test structure with asphalt single roof prior to
start of test.

-21-


1200

1000
800

S

©

5

3 600

Oo

Qa

E

Oo

£
400
200

0 z : 1 1

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Figure 32. Graph showing temperatures measured in the bedroom during the second test
(distances measured from ceiling downward).

-51-


1200
1000
800
S
2
>
o 600
oO
Qa
=
oO
e
400 | 4
j
200 - |
k
j
0 i L L

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Figure 41. Graph showing temperatures measured in the living room during the fourth test
(distances measured from ceiling downward).

- 60-


Table of Contents

Abstract...
Introduction
Experimental Configuratio:
Experiments
Full Scale Fire Tests
Cone Calorimeter Experiments
Results
Full Scale Fire Tests
Temperature Data...
Infrared Camera Data.
Cone Calorimeter Experiments
Uncertainty Analysis
Conclusions..........
Acknowledgements.
References
Appendix A — Cone Calorimeter Test Data

E
es
COMAAwWHK 1d

- iii -


Figure 21. Photograph of test structure at 900 s after ignition when front door has burned away.

- 40 -


Figure 19. Photograph of test structure at 540 s after ignition.

-38-


1200

1000
800
S
©
5
3 600
Oo
Qa
E
Oo
£
400
200
ot

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Figure 44. Graph showing temperatures measured in the south portion of the attic during the
fourth test (distances measured from roof peak downward).

-63-


Cone Calorimeter Experiments

The type of material, either plywood or OSB, which was used for the roofs of the structures is
one of the variables examined during this study. In an effort to develop additional information
about the materials and their response to fire exposure, samples were tested in the cone
calorimeter. The cone calorimeter was developed at NIST in the 1980’s [10], and it is presently
the most commonly used bench-scale rate of heat release apparatus [11]. There are national [12]
and international [13] standards documenting the apparatus and appropriate test procedures.
Heat release rate is determined by the oxygen consumption method [14]. The gas flow rate in
the exhaust duct is calculated from the pressure drop across and temperature at an orifice plate in
the duct.

The cone calorimeter consists of a heater, spark ignitor, sample holder, and load cell located
underneath an exhaust hood (Figure 25). Typically, the sample is located in the open with free
access of air to the combustion zone. The heater consists of a 5-kW electrical heating element
inside an insulated stainless-steel conical shell. Samples can be tested in either a horizontal or
vertical orientation. When tests are performed in the horizontal configuration, the specimen is
positioned approximately 25 mm (1 in) beneath the bottom plate of the cone heater. Flames and
products of combustion pass through a circular opening at the top of the heater. The heater can
expose samples to a maximum irradiance of approximately 100 kW/m’.

For piloted ignition tests, an electric spark ignitor is positioned at the top of vertical samples and
over the center of horizontal samples. Samples are typically 0.1 m (0.3 ft) by 0.1 m (0.3 ft), and
they can be wrapped with aluminum foil to minimize edge effects. Combustion products and
dilution air are extracted through the hood and exhaust duct by a high temperature fan. The flow
rate can be adjusted between 0.01 m°/s (0.35 ft’/s) and 0.03 m’/s (1.1 ft’/s). The volumetric flow
rate is maintained constant during testing. The sample is mounted on a load cell to determine
mass loss rate during a test, and smoke obscuration is measured using a laser light source.
Finally, the concentrations of carbon dioxide, carbon monoxide, and other gases are measured
using appropriate instruments.

Three replicate tests of each sample were conducted at external heat fluxes of 35 kW/m? and
70 kW/m. For each test, the 0.1 m (0.3 ft) square sample was oriented horizontally under the
cone heater. Data were recorded until approximately 20 % to 25 % of the original mass
remained.


1200

1000
800
S
o
5
® 600
oO
Qa
€
oO
fa
400
Tes
he
200
fe ee
0 “ \ Lo
0 200 400 600 800 1000 1200 1400
Time (s)

1600

Figure 31. Graph showing temperatures measured in the living room during the second test

(distances measured from ceiling downward).

- 50-


1200

1000

800
Ss
©
5

® 600
cy
Qa
&
o
&

400

200

0 : ! !

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Figure 37. Graph showing temperatures measured in the bedroom during the third test (distances
measured from ceiling downward).

- 56-


momentarily extending into the attic area through the ceiling ventilation louvers. A comparison
of Figures 33 and 34 suggests that the attic access panel and possibly a portion of the ceiling near
the ignition location failed at 400 s. The brief peak in Figure 34 at 725 s is probably the ignition
of plastic light boxes in the ceiling. The attic area reaches a flashover condition at about 900 s.
A portion of the roof under the fire fighter mannequins collapses approximately 4 min after
flashover in the attic area. The temperature data obtained on the roof surface beneath the fire
fighter mannequin boots during the fire test is shown in Figure 35. As the attic space approaches
flashover conditions at about 800 s, the temperatures under the boots increase to 750 °C

(1380 °F). At approximately 1020 s, the roof structure begins to collapse.

The temperature histories obtained for the third test are shown in Figures 36 through 40. As with
the other tests, the temperatures in the living room rise rapidly at the start of the third test. At
approximately 120 s, the space reaches temperatures indicative of flashover (Figure 36). After
flashover, the environment becomes stratified with temperatures ranging from 300 °C (570 °F) to
600 °C (1110 °F). At about 550 s, the temperatures in the lower part of the living room increase
producing an almost uniform environment of between 550 °C (1020 °F) and 600 °C (1110 °F).
Just prior to a portion of the ceiling collapsing at about 700 s, the temperatures in the living room
increase to about 700 °C (1290 °F). After collapse of a portion of the ceiling, the temperatures
initially decrease then increase to 700 ° C (1290 °F) to 800 °C (1470 °F). Collapse of a portion
of the roof occurs at about 960 s. Prior to collapse of a portion of the ceiling, the bedroom
temperatures remain well below 600 °C (1110 °F) (Figure 37). For the first 400 s of the test, the
temperatures in both the north (Figure 38) and south (Figure 39) portions of the attic grow slowly
to a peak of about 150 °C (300 °F). The temperature spikes during this period are indicative of
flames momentarily extending into the attic area through the louvers and other ceiling
penetrations (Figure 6). Once materials located in the attic start burning, the temperatures
increase reaching a sustained maximum of 550 °C (1020 °F) with a momentary peak above

600 °C (1110 °F). When the roof collapses at 960 s, the attic temperatures initially increase then
decrease rapidly as suppression is initiated. The temperatures under the fire fighter mannequins’
boots remain close to ambient until the roof collapses at 960 s when the mannequins are
enveloped in flame and removed (Figure 40).

The temperature histories obtained for the fourth test are shown in Figures 41 through 45. The
temperature data obtained in the living room (Figure 41) indicates that the fire grew rapidly
producing temperatures in excess of 600 °C (1110 °F). The environment in the living room
remained at flashover temperatures and well mixed until about the time of roof collapse. The
environment in the bedroom (Figure 42) remains stratified with a peak temperature of 420 °C
(790 °F) until some portion of the ceiling fails at 450 s. After ceiling failure, the temperatures
become somewhat erratic varying between 400 °C (750 °F) and almost 800 °C (1470 °F). At
approximately 800 s, the temperatures in the bedroom become uniform and decrease then rapidly
increase then decrease again. The most likely cause of this phenomenon is failure of additional
portions of the ceiling as a result of flashover in the attic space. Temperature increase in both the
north (Figure 43) and south (Figure 44) parts of the attic is relatively continuous with only slight
discontinuities at about 450 s and 850 s. These discontinuities indicate ignition of materials in

-10-


-li-


Figure 12. Photograph of “living room” showing ignition location in corner of couch under
newspaper.

-31-


wo 22-2 2--------------------- NIST/BFRL/MPG --------------------------------
C:\CONE171\RAWDATA\010731A6.CDT

Test Date : 31-Jul-01 Test Time : 02:11 p.m. Operator : Michael Smith

Test Scans
Test Length

227 scans, 3 secs/scan
561.41 secs

Sample Surface Area : 0.01000 m2
Radiant Heat Flux  : 35.0 kW/m2
Sample Orientation : Horizontal
Measured Exh. Flow : 0.024 m3/sec
Orifice Plate : 57 mm

Sample Material
External 5 PLY Plywood
SAMP.3

Pre-test Comments:

Samp.in double density alumn.pan edge control.
Thermal absorber applied.
Samp.wt.=62.6g,Samp.t+pan wt.=65.5g.

Post-test Comments:
Samp.exhibited a uniform combustion process
without any thermal anomalies to report.

aaa Reduction Parameters ---W--~-------- 9-993 -2n2nnnnnnnnnnnnnnnnnnn

C-Factor (Methane) : 0.04381603
Conversion Factor : 13.100 MJ/kg 02
Baseline 02 Reading : 20.986 3%
Baseline C02 Reading : 0.05039 %
Baseline CO Reading : 0.00009 %

Sanaa” Test Results -------9--9 9-92 n nnn nnn nnn nnn nn nnn nnn nnn nnn

238.41 kW/m2 at 415.00 secs
124.83 kW/m2
143.02 kW/m2
109.21 kW/m2
102.26 kW/m2
63.66 MJ/m2
13.17 MJ/kg

Peak Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Total Heat Released
Average Effective HOC

Average Specific Ext Area : 56.65 m2/kg
Average Mass Loss Rate: H 10.248 g/s*m2
Entered Initial Specimen Mass : 65.50 g
Measured Final Specimen Mass : 17.16 9g
Average CO Yield : 0.00183 kg/kg
Average C02 Yield : 1.38610 kg/kg
Time to sustained Ignition H 54.23 secs

-73-


[19]  Twilley, W. H. and Babrauskas, V., “User's Guide for the Cone Calorimeter,” NBS SP

745, National Institute of Standards and Technology, Gaithersburg, MD, August 1988.
Bryant, R.A., Womeldorf, C.A., Johnsson, E.L., and Ohlemiller, T.J., “Radiative Heat
Flux Measurement Uncertainty,” Fire and Materials, Vol. 27, No. 5, pp. 209-222, 2003.

[20]

-19-


NISTIR 7094

Structural Collapse Fire Tests:
Single Story, Wood Frame Structures

David W. Stroup

Nelson P. Bryner

Jack Lee

Jay McElroy

Gary Roadarmel

William H. Twilley

Fire Research Division

Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899-8661

March 2004

) FEMA

Sree’

Department of Homeland Security U.S. Department of Commerce
Tom Ridge, Secretary Donald L. Evans, Secretary
Federal Emergency Management Agency Technology Administration
Michael D. Brown, Under Secretary of Emergency _ Phillip J. Bond, Under Secretary for Technology
Preparedness and Response National Institute of Standards and Technology
United States Fire Administration Arden L. Bement, Jr., Director

R. David Paulison, Administrator


Figure 24. Photograph of test structure at 1140 s after ignition when suppression has been
completed.

-43-


Figure 8. Photograph showing “living room” with furniture, cabinets, and thermocouple array.

-27-


Figure 17. Photograph of test structure at 180 s after ignition.

-36-


Bed

Thermocouple
Array

Dresser

O

Table
& Lamp

Thermocouple
/ Array

Loveseat

Figure 3. Plan view of generic test structure showing approximate placement of furniture and
other items within structure (not to scale).

-22-


Two mannequins outfitted in fire fighter turnout gear with self-contained breathing apparatus
were placed on the roof of each structure during the test. Each fire fighter mannequin had a mass
of approximately 127 kg (280 Ib) with gear, and they were positioned on the roof using metal
stands. One fire fighter was placed in a bending position while the second stood upright (Figure
1). Thermocouples were located in contact with the roof surface under the left and right boot of
each fire fighter mannequin. The tiles were removed from under the mannequins’ boots for tests
3 and 4. A roof mounted air conditioning unit was also placed on the roof of each structure.

Each air conditioning unit had an approximate mass of 227 kg (500 Ib) and was placed on the
sloped portion of the roof opposite the fire fighter mannequin locations.

Each test was documented using standard video, infrared cameras, and still photographs. Two
separate infrared cameras monitoring different portions of the electromagnetic band were used
during the tests. One of the infrared imagers, Camera A provided less quantitative temperature
data, but was representative of infrared cameras typically used by fire departments. The other
infrared imager, Camera B, provided significantly more resolution in temperature data, different
measurement ranges, emissivity factors, adjustable sensing spans, and calibration capability, but
it was not designed for fire fighter use. The video and infrared cameras were mounted on a fire
department ladder truck. During each fire test, the ladder with the standard video and two
infrared cameras was elevated to provide a similar overhead view of each structure for the three
cameras.

Experiments
Full Scale Fire Tests

Two fires were ignited simultaneously in each structure using electric matches. Electric matches
are matchbooks with a short length of Ni-Chrome wire wrapped around the match heads. When
a small electric current passes through the wire, the wire heats up and ignites the matchbook.
One electric match was placed in a slit in the couch in the front room and covered with paper
towels and newspaper (Figure 12). A second electric match was positioned in a slit in the chair
in the back room and covered with paper towels and newspaper (Figure 13).

The fires were ignited in each room simultaneously and allowed to grow to flashover. Flashover
occurs when multiple combustible items in a room ignite as a result primarily of being heated by
the intense thermal radiation from the hot upper layer. At flashover, the room environment is
characterized as well stirred with temperatures throughout the space being relatively uniform.
Gas temperatures in the room typically exceed 600 °C (1110 °F). During this test series, the fire
ultimately spread into the attic space and eventually caused collapse of a portion of the roof
structure. For this test series, collapse was assumed to occur when the portion of the roof
supporting the fire fighter mannequins failed and allowed fire to envelope the mannequins. As
the roof structure collapsed, the fire fighter mannequins were removed using a fire department
crane. Once the mannequins were removed, the fire was extinguished using water or a

-6-


1200

1000
800

S

©

5

3 600

Oo

Qa

E

Oo

£
400
200

0 1 1

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Figure 39. Graph showing temperatures measured in the south portion of the attic during the
third test (distances measured from roof peak downward).

- 58-


wo 22-2 2--------------------- NIST/BFRL/MPG --------------------------------
C:\CONE171\RAWDATA\010731A7.CDT

Test Date : 31-Jul-01 Test Time : 02:46 p.m. Operator : Michael Smith

Test Scans 171 scans, 3 secs/scan

Test Length : 393.60 secs
Sample Surface Area : 0.01000 m2
Radiant Heat Flux > 70.0 kW/m2
Sample Orientation : Horizontal
Measured Exh. Flow : 0.024 m3/sec
Orifice Plate : 57 mm
Sample Material :

External Oriented Strandboard

SAMP.1

Pre-test Comments:

Samp.in double density alumn.pan edge control.
Thermal absorber applied.
Samp.wt.=72.3g,Samp.t+pan wt.=75.6g.

Post-test Comments:
Samp.exhibited a uniform combustion process
without any thermal anomalies to report.

aaa Reduction Parameters ---W--~-------- 9-993 -2n2nnnnnnnnnnnnnnnnnnn

C-Factor (Methane) : 0.04381603
Conversion Factor : 13.100 MJ/kg 02
Baseline 02 Reading : 20.989 %
Baseline C02 Reading : 0.05890 %
Baseline CO Reading : 0.00009 %

Sanaa” Test Results -------9--9 9-92 n nnn nnn nnn nnn nn nnn nnn nnn nnn

325.77 kW/m2 at 34.00 secs
219.88 kW/m2
263.24 kW/m2
223.34 kW/m2
223.88 kW/m2
84.46 MJ/m2
14.20 MJ/kg

Peak Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Average Heat Release Rate
Total Heat Released
Average Effective HOC

Average Specific Ext Area : 117.30 m2/kg
Average Mass Loss Rate: H 16.520 g/s*m2
Entered Initial Specimen Mass : 75.60 g
Measured Final Specimen Mass : 16.10 g
Average CO Yield : 0.00359 kg/kg
Average C02 Yield : 1.46371 kg/kg
Time to sustained Ignition H 10.55 secs

-74-


Laser extinction beam including
\ lomperature measurement

— Temperature and differential pressure
\ measurements taken here

F -Soot sample tube location

Vertical orientation

Figure 25. Schematic drawing of the cone calorimeter.

-44-

~ Sample

Load cell


1200

1000

800
S
g
3

® 600
cy
ror
&
o
&

400

200

Z ai ene B. —
0 L i

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Figure 27. Graph showing temperatures measured in the bedroom during the first test (distances
measured from ceiling downward).

- 46 -


Results
Full Scale Fire Tests

Temperature Data

The temperature histories obtained for the first test are shown in Figures 26 through 30. As the
fire in the living room grows to flashover, the stratified fire environment is evident from the
distinct temperature histories obtained at the eight sampling locations (Figure 26). At about

200 s, the temperature plots indicate a “well stirred environment” with an average temperature of
about 500 °C (930 °F). The fire in the bedroom takes longer to reach flashover temperatures; it
reaches that point at about 420 s. At this point, the environment becomes well mixed with a
temperature of about 600 °C (1100 °F) (Figure 27). Both the north (Figure 28) and south (Figure
29) thermocouple arrays in the attic indicate a stratified environment until about 700 s. The two
peaks evident in both figures, one at about 180 s and the second at 200 s to 250 s, are most likely
the result of periodic flame penetration into the attic space through the ceiling penetrations
(Figure 6). At about 700 s, flashover appears to have occurred in the attic with the environment
becoming well mixed at an average temperature of 750 to 800 °C (1380 to 1470 °F). The
temperature plots suggest that some portions of the ceiling begin failing at about 800 s. In
addition, the front door failed at about 840 s. The roof begins to collapse at 1050 s and
suppression is started at 1120 s. The temperature data obtained on the roof surface beneath the
fire fighter mannequin boots during the fire test is shown in Figure 30. Once flashover occurs in
the attic at about 700 s, the temperatures under the boots increase rapidly to 800 °C (1470 °F),
approximately the temperature within the attic space. Subsequently, the temperatures decrease
correspondingly with decreasing temperatures within the attic space, possibly the result of failure
of the ceiling. The temperatures gradually increase until roof collapse at which point the
mannequins become surrounded by flames until their removal.

The temperature histories obtained for the second test are shown in Figures 31 through 35. In the
living room, the fire grows to a temperature indicative of impending flashover, approximately
600 °C (1100 °F) within 180 s after ignition. After this initial period, the fire environment
becomes stratified with a temperature gradient of 300 °C (570 °F) to 550 °C (1020 °F) for a
period of about 180 s (Figure 31). At approximately 350 s after ignition, the entire living room
area appears to flashover with a peak temperature of 700 °C (1300 °F). At this point, the
environment in the living room becomes well mixed with a uniform temperature throughout
most of the remainder of the test. The decrease in temperature occurring at approximately 400 s
is the result of failure of some portion of the living room ceiling. After the fire begins spreading
into the attic area, temperatures in the living room begin a steady climb to a peak of 1200 °C
(2200 °F). The front door fails at about 840 s leading to a reduction in living room temperatures.
Except for a few brief moments, the temperatures in the bedroom area never exceed 600 °C
(1110 °F) (Figure 32). With the exception of the point at which the roof section collapsed at
1020 s, the environment in the bedroom remains stratified throughout the duration of the test.
The first peak evident in Figures 33 and 34 at 180 s is most likely the result of flames

-9-