Performance of Thermal Exposure Sensors in

Personal Alert Safety System (PASS) Devices

Nelson Bryner

Daniel Madrzykowski

David Stroup

NISTIR 7294
NISTIR 7294

Performance of Thermal Exposure Sensors in

Personal Alert Safety System (PASS) Devices

Nelson Bryner

Daniel Madrzykowski

David Stroup

Building and Fire Research Laboratory

National Institute of Standards and Technology

Gaithersburg, MD 20899-8661

September 2005

U.S. Department of Commerce

Carlos M. Gutierrez, Secretary

Technology Administration

Michelle O'Neill, Acting Under Secretary of

Commerce for Technology

National Institute of Standards and Technology

William A. Jeffrey, Director

Department of Homeland Security

Michael Chertoff, Secretary

U.S. Fire Administration

R, David Paulison, Administrator
Table of Contents

List of Figures...............................................................................................................................iii

List of Tables................................................................................................................................. v

List of Tables................................................................................................................................. v

Abstract.......................................................................................................................................... 1

II. Thermal Exposure Sensors in PASS Devices....................................................................... 3

III. Experimental Apparatus ....................................................................................................... 6

A. Laboratory Experiment – Static Oven............................................................................. 6

B. Laboratory Experiment – Flow Loop .............................................................................. 8

C. Full Scale Experiments- Mannequin Tests.................................................................... 10

D. Analog Signal from PASS Devices............................................................................... 13

E. Vibration or Shaker Device ........................................................................................... 15

F. Data Acquisition System................................................................................................ 15

IV. Results................................................................................................................................... 16

A. Static Oven Tests........................................................................................................... 16

B. Flow Loop Tests............................................................................................................ 19

C. Full-Scale Mannequin Experiments .............................................................................. 22

D. Uncertainty Analysis..................................................................................................... 27

V. Discussion.............................................................................................................................. 38

A. Thermal Exposure Sensor Activation............................................................................ 38

B. Standard Test Protocol................................................................................................... 42

VI. Conclusions.......................................................................................................................... 43

VII. Acknowledgements............................................................................................................. 44

VIII. References.......................................................................................................................... 44

IX. Other Resources................................................................................................................... 45
iii

List of Figures

Figure 1. Personal Alert Safety System (PASS) devices from various manufacturers. ................ 4

Figure 2. Temperature response curves......................................................................................... 5

Figure 3. Schematic of static oven apparatus................................................................................. 7

Figure 4. Photograph of static oven apparatus............................................................................... 7

Figure 5. Schematic of flow loop experimental apparatus. ........................................................... 9

Figure 6. Photograph of flow loop experimental apparatus........................................................... 9

Figure 7. Instrumented mannequin for full-scale field experiments............................................ 11

Figure 8. Thermocouple and mannequin elevations. ................................................................... 11

Figure 9. PASS devices positioned on front of mannequin......................................................... 12

Figure 10. PASS devices positioned on rear of mannequin......................................................... 12

Figure 11. Full-scale townhouse fire test used to expose instrumented mannequin.................... 13

Figure 12. Diagram of townhouse floor plan............................................................................... 14

Figure 13. Static oven gas temperature versus PASS analog signal for device A-2. .................. 17

Figure 14. Static oven gas temperature versus PASS analog signal for device B-3.................... 17

Figure 15. Static oven gas temperature versus PASS analog signal for device C-2.................... 18

Figure 16. Flow loop gas temperature versus PASS analog signal for device A-1..................... 18

Figure 17. Flow loop gas temperature versus PASS analog signal for device B-4. .................... 20

Figure 18. Flow loop gas temperature versus PASS analog signal for device C-3. .................... 20

Figure 19. Gas temperatures versus time for full-scale townhouse burn in Unit 1. .................... 23

Figure 20. Thermal heat flux versus time for full-scale townhouse burn in Unit 1..................... 23

Figure 21. Temperature (Room) and thermal sensor activation for PASS device A in Unit

1............................................................................................................................... 24

Figure 22. Temperature (Room) and thermal sensor activation for PASS device C in Unit

1............................................................................................................................... 24

Figure 23. Temperature (Mannequin front and rear) and thermal sensor activation for

PASS device A in Unit 1......................................................................................... 25

Figure 24. Temperature (Mannequin front and rear) and thermal sensor activation for

PASS device C in Unit 1. ........................................................................................ 25

Figure 25. Gas temperatures versus time for full-scale townhouse burn in Unit 2. .................... 30

Figure 26. Thermal heat flux versus time for full-scale townhouse burn in Unit 2..................... 30

Figure 27. Temperature (room) and thermal sensor activation for PASS device A in Unit

2............................................................................................................................... 31

Figure 28. Temperature (room) and thermal sensor activation for PASS device C in Unit 2 ..... 31

Figure 29. Temperature (mannequin front and rear) and thermal sensor activation for

PASS device A in Unit 2......................................................................................... 32

Figure 30. Temperature (mannequin front and rear) and thermal sensor activation for

PASS device C in Unit 2 ......................................................................................... 32

Figure 31. Gas temperatures versus time for full-scale townhouse burn in Unit 3. .................... 33

Figure 32. Thermal heat flux versus time for full-scale townhouse burn in Unit 3..................... 33

Figure 33. Temperature (room) and thermal sensor activation for PASS device A in Unit

3............................................................................................................................... 34
iv

List of Figures cont'd

Figure 34. Temperature (room) and thermal sensor activation for PASS device C in Unit

3............................................................................................................................... 34

Figure 35. Temperature (mannequin front and rear) and thermal sensor activation for

PASS device A in Unit 3......................................................................................... 35

Figure 36. Temperature (mannequin front and rear) and thermal sensor activation for

PASS device C in Unit 3. ........................................................................................ 35
v

List of Tables

Table 1. Static oven exposure tests for PASS devices................................................................. 19

Table 2. Flow loop exposure tests for PASS devices. ................................................................. 21

Table 3. Full-scale townhouse exposure tests for PASS devices (room peak temperatures). ..... 28

Table 4. Full-scale townhouse exposure tests for PASS devices (mannequin peak

temperatures)........................................................................................................... 29

Table 5. Uncertainty in static oven and flow loop experimental data. ........................................ 36

Table 6. Uncertainty in full scale experimental data. .................................................................. 37
1

Performance of Thermal Exposure Sensors in Personal Alert Safety System

(PASS) Devices

by

Nelson Bryner

Daniel Madrzykowski

David Stroup

Abstract

Fire fighters can be overcome by heat or smoke of a fire and may be unable to alert other

fire ground personnel to their need for assistance. Personal Alert Safety System (PASS) devices

are designed to signal for aid if a fire fighter becomes incapacitated. Thermal exposure sensor

technology has already been included in a number of PASS devices, but no standard exists for

testing the performance of the thermal sensor.

A series of static oven, flow loop, and full-scale experiments were conducted to

demonstrate the performance of different PASS devices. This limited set of temperature versus

thermal sensor activation data indicates that sensors respond differently under static, flowing,

and radiation intense conditions. The full-scale data demonstrate that current thermal

sensing/PASS implementations are unlikely to provide a fire fighter with sufficient warning of

an acute thermal hazard. Current PASS devices may provide information to fire fighters about

their longer term exposure to thermal conditions, but there is a significant delay of 25 s to 120 s

before the fire fighter receives this alarm or information.

This limited series of experiments demonstrates the need to develop a standard testing

protocol to insure that all PASS devices provide adequate protection for fire fighters. This

testing protocol must evaluate the performance of thermal sensors under a range of fire

environments that fire fighters may realistically encounter on a routine basis. This experimental

data was used to develop a prototype standard test protocol which can used to quantify the

thermal sensor performance.

Keywords: Personal Alert Safety System, PASS, PASS device, thermal exposure, thermal

sensor, thermal response data
2

I. Introduction

Fire fighters can be quickly overcome by the heat or smoke of a fire and may be unable to

alert other fire ground personnel to their need for assistance. Personal Alert Safety System

(PASS) devices are designed to signal for aid if a fire fighter becomes incapacitated on the fire

ground. From 1994 to 1998, an average of 725 fire fighters per year were caught or trapped in

structure fires that resulted in injury or death of fire fighters, according to an analysis of National

Fire Incident Reporting System (NFIRS) data by the National Fire Protection Association

(NFPA) [1]. Fire fighters fatalities resulting from being caught or trapped in structures caused

15 deaths out of a total of 97 fire fighter fatalities according to NFPA statistics for 2002 [2] and

represented the third leading cause of fire fighter fatalities after stress/overexertion and struck by

objects [2]. US Fire Administration statistics for 2003 indicate that caught/trapped or collapse

accounted for 12 fire fighter fatalities in 2003 [3]. Two NFPA studies examined fatalities due

to structural collapse for 1979-1988 [4] and for 1983-1992 [5] and reported that 60 % of fire

fighter deaths in structures were caused by being caught or trapped in the structure. Brassell

and Evans [6] reported that this percentage increased to over 85 % for the period 1994 to 2002.

Fire fighter becoming caught or trapped in structures has been a major hazard for fire fighters for

the past 20 years. If properly implemented, the PASS device can serve as a platform for the

incorporation of additional and more innovative technology to help reduce fatalities and injuries

resulting from caught or trapped fire fighters.

Personal Alert Safety System devices are designed to signal for aid via an audible alarm

signal if a fire fighter becomes incapacitated on the fire ground. Typically, PASS devices sense

movement or lack of movement and activate a 95-decibel alarm signal if the lack of motion

exceeds a specific time period. The loud alarm signal alarm alerts other personnel that a fire

fighter has become motionless and may be incapacitated. The loud alarm helps to guide rescue

personnel to the location of the incapacitated fire fighter. Performance standards and testing

protocols for motion or lack of motion detectors is described by NFPA Standard 1982 [7]. While

the current NFPA Standard for PASS devices (NFPA 1982) requires only a motion detector,

some PASS device manufacturers are beginning to incorporate additional technology into PASS

devicesto improve fire ground safety. If properly implemented, new technology including

thermal sensors could significantly improve the safety and effectiveness of fire fighters on the

fire ground.

Thermal exposure sensor technology has already been included in a number of models of

PASS devices. However, there are currently no standards or testing protocols with which to

assess the performance of these thermal exposure sensors. While it is commendable that

manufacturers seek to include more technology in order to increase the safety of fire fighters, the

fire service does not have the resources to evaluate the thermal exposure sensor performance in

PASS devices. There is a need for a well-designed testing protocol that would include different

fire conditions that fire fighters typically encounter. This would allow the fire service to

understand better the performance characteristics of the thermal sensors. In addition, a

standardized testing protocol would allow the manufacturers to match the performance of their

devices with the requirements of the fire service.

In the future, additional capabilities and technologies may be incorporated into PASS

devices. Emerging technologies which would provide valuable capabilities to the fire service

include fire fighter location and tracking, fire ground accountability, toxic gas analyzers, and
3

physiological and stress monitors. It would also be useful if future PASS devices could

incorporate the capability to communicate information such as location, gas concentrations, and

heart rate to the incident commander outside the structure. It is critical that a standardized

testing protocol be in place as each these technologies are integrated into PASS devices so that

the fire service understands the performance as well as the limitations of their equipment. The

overall goal of this work is to improve the safety and effectiveness of fire fighters. To

accomplish this goal, the fire service must be able to incorporate state-of-the-art technology into

all of its equipment. But, in order for the fire service to integrate new technology safely, it must

be able to understand the performance and the limitations of this new technology.

The first part of this study examines the performance of the thermal exposure sensors in a

series of laboratory as well as real scale experiments. Exploring new technologies, such as fire

fighter locator, fire ground accountability, toxic gas analyzers, and physiological monitors,

which might enhance performance of future PASS devices and developing a prioritized plan to

incorporate new technology will be addressed in a separate report.

II. Thermal Exposure Sensors in PASS Devices

Thermal exposure sensor technology has been incorporated into motion detector PASS

devices by a number of manufacturers, but not all PASS suppliers have incorporated thermal

sensors into their devices. Examples of different PASS devicesare shown in Figure 1. Some

of the PASS devices that are shown in Figure 1 have been modified by adding external wires

which allowed the alarm signal to be monitored externally. This modification is discussed later

in this report. Not all the devices shown in Figure 1 incorporate thermal exposure sensors.

This thermal sensing capability is not required by NFPA Standard 1982. Currently, the lack of

an equipment standard or testing protocol for the thermal sensors has resulted in each

manufacturer developing their own specific implementation of thermal sensing technology.

Typically, the thermal sensor utilizes a single, small sensing element, usually less than 3.2 mm

(0.125 in) in diameter. The temperature-sensing component is located inside the case of each

PASS device. Each thermal sensor monitors a temperature and if the temperature exceeds a predetermined value for a specific period of time, the PASS device is designed to go into alarm.

The electronics necessary to process the temperature data are typically incorporated onto the

circuit board that collects and processes the information from the motion detector. The PASS

device generates a 95-decibel alarm signal when either the temperature sensor or motion detector

has been activated.

Fire fighters wear protective gear that effectively insulates them from the thermal

environment around them. At times, it is difficult for the fire fighter to appreciate how much

heat flux or thermal stress they have been exposed to during fire fighting operations. Thermal

sensor equipped PASS devices are worn on the outside of the protective gear and monitor the

thermal exposure. Thermal sensors continuously track the thermal environment and are

designed to alarm at pre-set exposure values when the set-point temperature is exceeded for a

Certain trade names and company products are mentioned in the text or identified in an illustration in order to

specify adequately the experimental procedure and equipment used. In no case does such identification imply

recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the

products are necessarily the best available for the purpose.
4

specified time period. The thermal environment can range from slightly elevated temperatures,

66 oC (150 oF) up to pre-flashover temperatures, 650 oC (1200 oF). A fire fighter may be able

to work for longer periods in slightly elevated temperatures, but must quickly escape high

temperature situations. Consequently, thermalsensing PASS devices must be able to warn the

fire fighter for a range of exposures; short duration at high temperatures and long duration at

slightly elevated temperatures.

Figure 1. Personal Alert Safety System (PASS) devices from various manufacturers.

Thermal sensing PASS devices use a temperature response curve to determine which

thermal exposures will activate an alarm. Two examples of temperature response curves are

shown in Figure 2. Once the thermal sensor temperature has exceeded the temperature response

value (above the temperature versus time curve) for a period of time that corresponds to that

temperature, the thermal sensor will activate an alarm. For example, a sensor designed to

follow the lower curve (Curve A in Figure 2) would alarm in less than 1 minute to a temperature

above 320 oC (600 oF). A sensor that is configured to the upper response curve (Curve B in

Figure 2) would require significantly longer time to respond, 3 minutes at a temperature of

320 oC (600 oF). For lower temperatures at around 66 oC (150 oF), the lower and upper curves

indicate a response time of 20 minutes and 25 minutes, respectively. If the thermal sensor

equipped PASS device is designed to monitor exposure to lower temperatures for longer periods

of time, either of the response curves would activate an alarm at 25 minutes of exposure to 66 oC

(150 oF). But, if the PASS device was designed to warn a fire fighter of an exposure to higher

temperatures for designed to Curve B. However, even a thermal sensor that alarms
5

200

400

600

800

1000

0

100

200

300

400

500

0 5 10 15 20 25 30 35

Te

m

p

erature, F

o

T

e

m

p

erature, C

o

Time, min

Response

Curve A

Response

Curve B

Figure 2. Temperature response curves.

after a 1 min exposure to 320 oC (600 oF), may not provide adequate time for a fire fighter to

escape a serious thermal threat.

A standard testing protocol would allow the fire service and manufacturers a method to

evaluate or characterize the performance of thermal sensors in PASS devices. The performance

characteristics can vary from manufacturer to manufacturer due to different sensing elements,

multiple sensing locations, e.g. inside PASS case or outside a case, and different temperature

averaging algorithms. A standard testing protocol would help ensure that every PASS device

responds to a basic set of fire conditions or thermal environments that may be encountered by a

fire fighter wearing a thermal sensing PASS device. It is important that the performance

characterized by the testing protocol be representative of the conditions a fire fighter may

experience.

But, the thermal environment that a fire fighter encounters can be complex. Fire

fighters may find themselves standing or crouching in a room full of hot combustion products

and smoke. In this scenario, the fire fighter is enveloped in a relatively static layer of hot gases.

If suppression has been initiated, water droplets and steam may also be present. Fire fighters

may also be moving through a smoke filled room or experience a situation where the smoke is

moving past them. In these circumstances, a fire fighter is immersed in a flowing smoke layer.

Fire fighters may also need to enter a room in which a fire is burning. Under these conditions, a

fire fighter is exposed to the intense thermal radiation that is produced by a hot fire. During

each of these scenarios, the fire fighter and PASS devices that they are wearing experience the

transfer of heat from the hot smoke or fire via conduction, convection, and/or radiation. To

understand the performance of the thermal exposure sensors, it is necessary to examine the

response of the thermal sensor and PASS device to these various conditions that may be

experienced by fire fighters.

The performance of thermal exposure sensors was documented for three different PASS

models from three different manufacturers. Through a series of lab- and full-scale experiments,
6

the overall performance of a PASS device to alarm in response to a specific thermal insult or

condition was evaluated. This limited set of experiments was designed to provide a better

understanding of the response characteristics of PASS devices equipped with thermal sensors in

order to help develop a standard test protocol.

These experimental series was not intended to be “product testing” and is too limited to

be used to rank the individual PASS devices. Since the focus of this work is to develop a

standard test protocol which does not favor any one specific thermal sensor technology, PASS

devices will only be identified as Model A, Model B, and Model C. Multiple PASS devices of

the same model from the same manufacturer will be identified as A-1, A-2, and A-3.

III. Experimental Apparatus

The performance of different PASS models from various manufacturers was examined

during experiments in a static oven, in a heated flow loop, and on a mannequin in field tests.

Four different models of PASS devices were exposed to static hot gases, flowing hot gases, or

real scale combustion gases. Three of the models had thermal sensors and one model did not.

This study will focus on the temperature versus alarm activation data for the three models that

incorporated thermal sensors. While not the focus of this study, the impact of repeated thermal

exposures on the motion repeated thermal exposures did not appear to impact the motion sensing

capability of the PASS devices, with or without the thermal sensor. The performance of

thermal sensor equipped PASS devices were examined in 60 tests in a static oven, 48 runs in a

heated flow loop, and four mannequin tests in townhouse fires.

The laboratory experiments involved exposing each thermal sensor equipped PASS

device to a series of different temperature environments in a static oven as well as a flow loop

that allowed hot air to flow past each device. Both the static oven and flow loop experiments

were designed to allow careful monitoring of the temperature around each PASS device and

when each PASS device alarmed. In each laboratory experiment, the temperature could be

increased gradually and in a controlled fashion. For each case, static or flowing, the temperature

of the hot gases was increased until the thermal sensor alarmed.

Field experiments were designed to expose each PASS device to realistic fire conditions

in which the temperatures may increase more quickly (and realistically) than in the laboratory

experiments. Six PASS devices were mounted on a mannequin that was also instrumented with

thermocouples on the front, rear, inside, and top of the protective gear. This instrumented and

PASS equipped mannequin was then exposed to a series of townhouse burns when the

temperature and time history were monitored until the thermal sensors alarmed.

A. Laboratory Experiment – Static Oven

For each of the static oven tests, either a single or a pair of PASS devices was suspended

inside a small electric resistance oven (Figures 3 and 4) with internal dimensions of 0.44 m

(17.3 in) wide x 0.29 m (11.6 in) deep x 0.39 m (15.5 in) height. This oven temperature was

continuously variable between 18 oC (64 oF) and 250 oC (480 oF) and thermostatically controlled.
7

250

200

150

100

0

50

On

Off

44 cm wide x 30 cm deep

40 cm

Electrical Resistance Oven

Vibration

Inducing

Device

PASS

Analog

Signal

Thermocouple

Data Lines

Data Acquisition

System

Figure 3. Schematic of static oven apparatus.

Figure 4. Photograph of static oven apparatus.
8

Each device was suspended approximately in the center of the oven and connected to the data

acquisition system. Each PASS device was instrumented front and rear with Chromel-Alumel

thermocouples with bead diameters of 2 mm (0.08 in) diameter. Additional thermocouples were

placed in the center of the oven and outside the oven to monitor the gas temperature and ambient

temperature, respectively. These thermocouples allowed the PASS device, gas, and ambient

temperatures to be monitored continuously. Prior to inserting the PASS devices into the static

oven, each device received a new 9 Volt battery.

For each oven test, the initial oven temperature was recorded, typically being between

18 oC (64 oF) to 28 oC (82 oF). Each PASS device or pair of PASS devices was mounted along

the centerline of the oven. Once mounted inside the oven, each PASS devices was connected to

the data acquisition system and to a vibration-inducing device. The vibration or shaker device

induced a slight movement (vertical direction) in each PASS devices in order to prevent false

alarms due to the motion sensor. The oven door was closed and the oven temperature was reset

to 40 oC (105 oF). The temperature of the gas as indicated by a thermocouple in the center of the

oven was allowed to reach the initial temperature set point. After ten minutes if the PASS

device had not alarmed, the temperature set point was increased by 5 oC (9 oF). This process of

increasing the temperature and exposing the PASS device to that temperature for 10 minutes was

continued until the PASS alarmed or the oven temperature exceeded 120 oC (250 oF).

If two PASS devices had been mounted in the oven, then the device that had alarmed was

removed from the oven and the test continued with the other PASS device alarm. After each

PASS device had alarmed, the PASS devices were removed and the oven was allowed to cool

down and then the procedure was initiated with the next two PASS devices. Each set of

experiments for a given PASS device included at least three runs in the oven and at least two

PASS devices from each manufacturer were exposed.

B. Laboratory Experiment – Flow Loop

For each of the flow loop tests, a single PASS device was suspended inside a section of a

larger flow loop (Figures 5 and 6). The flow loop was originally designed as part of a test

apparatus used to conduct water sprinkler plunge tests [8]. The internal dimensions of the test

section were 0.2 m( 8 in) deep x 0.2 m (8 in) height x 0.36 m (14.25 in) wide. The blower

necessary to move the air flow and the electrical resistance heaters required to maintain the gases

at a specific temperature are located in other sections of the apparatus. The gas temperature of

the flow loop was continuously variable between 18 oC (64 oF) and 150 oC (300 oF) and

thermostatically controlled. The flow velocity of the flow loop was variable from 0.25 m/s

(0.6 mph) to 5 m/s (11.2 mph) and was continuously monitored via a bi-directional probe.

The flow loop featured a hinged access door that formed the top wall or roof of the test

section. This access door could be opened and moved out of the way to allow a second top wall

or removable section to be quickly positioned into the opening. Each PASS device was

mounted on the removable section for quick insertion and removal. Each instrument was

mounted on a horizontal metal rod that was suspended via thin wires from the removable section.
9

Flow

St raight ening

Sect ion

Ac cess

Door

(Open)

PASS

Flow

Flow

Heat

Plenum

Electric Blower

Resistanc e

Heater

PASS

Device

Data

Acqui sition

System

The rmo cou ple

Da ta Li nes

PA S S

An alog

Sig nal

Vibrati on

Induc ing

Devic e

Control Panel

Figure 5. Schematic of flow loop experimental apparatus.

Figure 6. Photograph of flow loop experimental apparatus.

When the removable section was inserted into the flow loop, the PASS device was positioned so

that the front of the device faced into the flow of the hot air. The PASS device did not have a

backer board or support plate behind the device case. Each PASS device was instrumented front

and rear with Chromel-Alumel thermocouples with bead diameters of 2 mm (0.08 in) diameter.

Additional thermocouples were placed in the center of the flow and outside the loop to

monitor the gas temperature and ambient temperature, respectively. These thermocouples
10

allowed the PASS device, gas, and ambient temperatures to be monitored continuously. Prior to

inserting the PASS devices into the flow loop, each device received a new 9 Volt battery. Each

PASS was then mounted on a removable section, connected to the data acquisition system and

the vibration-inducing device.

After the flow loop had reached a velocity of 1.3 m/s (3 mph), and maintained that

velocity for several minutes, the temperature of the flow was recorded, typically being between

24 oC (75 oF) to 28 oC (82 oF). The PASS device was turned on, the shaker device was

activated, and the device equipped removable section was placed into the flow section. After

checking to insure that each PASS device was not alarming due to lack of motion, the removable

section and PASS device were lifted out of the flow section. The hinged access door was closed

and the flow loop temperature was reset to 40 oC (105 oF).

For each of the flow loop tests, a PASS device was quickly inserted into a flow of heated

air. If the device did not alarm after ten minutes of exposure, the PASS device was removed.

The temperature of the air was increased by 10 oC (18 oF). This process of increasing the

temperature and exposing the PASS device to that temperature for 10 minutes was continued

until the PASS alarmed or the flow loop air temperature exceeded 120 oC (250 oF). These

experiments were repeated at least three times with each of the different PASS devices.

C. Full Scale Experiments- Mannequin Tests

Full-scale experiments were conducted to examine the performance of thermal exposure

sensors under more realistic conditions than the static or flow loop tests provided. For each fullscale experiment, a mannequin that was instrumented with six PASS devices (Figures 7 - 10)

was inserted into a series of townhouse burns (Figure 11). During a series of burns in identical

townhouse units, an instrumented mannequin was positioned inside and exposed to different fuel

packages. The mannequin was located between the dining room and living room initially and

could be retracted to the kitchen (Figure 12). Townhouse Unit 1 (Figure 12) was only furnished

with carpeting while townhouse Unit 2 (Figure 12) and Unit 3 (not shown) were furnished with

sofa, chair, lamp, end table and carpeting. For Unit 1and Unit 2, 1.0 L (0.26 gal) of gasoline

was poured on the center of the carpet and ignited. Unit 3 was ignited using an electric match in

crumpled up newspaper in the corner of the sofa. Fuel package in Unit 1 was not sufficient to

allow the fire to approach flashover so active suppression was unnecessary. Since the fuel

package was sufficient to achieve flashover in Unit 2 and 3, each fire was allowed to approach

flashover, but water from a 3.8 cm (1.5 in) hose line was used to suppress each fire as flashover

began. The response of the PASS devices was continuously monitored throughout each

exposure. The mannequin was also instrumented with thermocouples to track the temperatures

on the front, rear, and top of the mannequin. Additional thermocouples and total heat flux

gauges were also positioned next to the mannequin.

A full-size, kneeling mannequin was clothed in protective pants and jacket, boots, gloves

and helmet. Three PASS devices were positioned on the chest of the mannequin as shown in

Figure 7, 8, and 9. The centerline of each PASS device, front and rear, was 0.95 m (37.4 in)

above the floor. Three devices were also mounted on the back or rear side of the mannequin

(Figure 10) at an elevation of 0.95 m (37.4 in) above the floor. The mannequin was also

instrumented with thermocouples on the outside of the protective gear jacket near where the six

PASS devices were mounted, the top of both shoulders, and on the top of the helmet. Two
11

Figure 7. Instrumented mannequin for full-scale field experiments.

Figure 8. Thermocouple and mannequin elevations.
12

Figure 9. PASS devices positioned on front of mannequin.

Figure 10. PASS devices positioned on rear of mannequin.
13

Figure 11. Full-scale townhouse fire test used to expose instrumented mannequin.

total heat flux gauges, one oriented parallel to the floor and one positioned perpendicular to the

floor, were mounted next to the mannequin to monitor horizontal and vertical components of

thermal radiation and heat flux. A vertical array of thermocouples was located next to the

mannequin. Thermocouple beads with diameters of 2 mm (0.08 in) were spaced at 0.31 m

(12 in) intervals from ceiling to floor. The thermocouple elevations are shown on Figure 8.

The mannequin was positioned so that it faced the fuel package that was to be ignited. The

kneeling mannequin was mounted on a platform 0.05 m (2 in) above the floor. The platform

incorporated wheels that allowed the mannequin to be withdrawn into the kitchen area. If the

specific fuel/ventilation/suppression configuration required the room to extend to flashover then

the mannequin was pulled back or retreated into the kitchen area (Figure 12). Once the

mannequin had been retreated into the kitchen, a fire resistant curtain was dropped in front of the

mannequin to shield it from additional thermal radiation and hot gases.

D. Analog Signal from PASS Devices

Each PASS device was modified so that the alarm/no alarm status of each individual

device could be continuously monitored by a data acquisition system. Two different techniques

were used to extract an analog signal from each PASS device as it alarmed. The first method

was to monitor the voltage signal at the piezo-electric disk while the second method was to track

the battery voltage. PASS devices typically incorporate a piezo-electic disc to generate a 95

decibel alarm signal. When a voltage is applied across a piezo-electric material, such as quartz

or barium titanate, the electrical energy is converted to mechanical energy. The mechanical

motion of a disc creates the alarm signal. Monitoring the piezo-electric voltage provided a

relatively stable signal that typically was near zero until the device began to alarm. When the

alarm was activated the amplitude increased dramatically and exhibited high frequency
14

Kitchen Kitchen

Living

Room

Dining

Room

Living

Room

Dining

Room

Thermocouple Video Camer a

Radiometer

Mannequin

Exposed

Mannequin

Retracte d

Chair

Sofa

Unit 1 Unit 2

Figure 12. Diagram of townhouse floor plan.

fluctuations. The voltage to the piezo-electric disk could also be interrupted to disable the 95

decibel alarm signal. The second method of monitoring did not disable the alarm signal, but

simply tracked the battery voltage. Tracking the battery voltage resulted in signal that steadily

declined as the device functioned normally. This steady decline was expected as the electronics

used electrical energy stored in the battery. As the alarm was activated, a dramatic decrease in

the voltage occurred as the device began to draw more and more electrical energy out of the

battery.

Both techniques worked equally well at marking the activation of the alarm. In either

situation, there was a dramatic change in the voltage signal when the PASS device alarmed. A

simple extension of monitoring the voltage to the piezo-electric disc was to interrupt the voltage

and this disabled the alarm signal. Temporarily deactivating the alarm signal allowed personnel
15

to conduct the test series without additional ear protection and caused less disturbance to nearby

laboratories and offices. In the field experiments, having all six of the PASS device on the

mannequin in alarm simultaneously would have required the operator to wear ear protection,

earplugs or ear muffs. Monitoring the piezo-electric signal in the field again allowed for the

experiments to be conducted without ear protection.

E. Vibration or Shaker Device

As each thermal sensor was being exposed to a different thermal environment, whether it

was a static oven, flow loop, or full-scale fire test, it was necessary to prevent the PASS device

from alarming due to lack of motion. The lack of motion detector and thermal exposure sensor

shared the same piezo-electric disks to generate the 95 decibel alarm signal. An alarm from the

lack of motion could have been confused with the alarm from the thermal sensor. To prevent

this confusion, each PASS device was connected to a shaker or vibration inducing device. The

shaker cause a relatively small movement, typically less than 0.013 m (0.5 in), and this was

sufficient motion to prevent the motion detector from activating the alarm. For the lab-scale

tests in the static oven and flow loop the shaker device was attached to each PASS device via

high temperature wire and periodically lifted the device and allowed the PASS to drop back

down approximately 4 to 5 times a minute.

For the field experiments, it was impractical to use the lab-scale device to shake the

PASS devices mounted on the mannequin. The lab-scale shaker was relatively large and was

powered via 120 volt AC house electricity. For the field work, smaller battery powered

shakers, each 2.54 cm (1 in) diameter and 8.9 cm (3.5 in) long, were attached to the harness that

held the three PASS devices on the front and three devices on the rear of the mannequin. Two

of the battery powered vibration devices appear as white cylindrical shaped objects in between

the PASS devices in Figure 9 and blue rectangles in Figure 8. Each of the small shakers

incorporated a small direct current (DC) motor that moved a small weight that resulted in a slight

movement of the shaker. Since each of the vibration inducing devices was attached to the same

harness the secured the PASS devices, the vibrations were transmitted to the PASS devices.

Multiple shakers were necessary to obtain sufficient movement or vibrations to prevent the

PASS devices from alarming due to lack of motion.

F. Data Acquisition System

The analog voltage signal from each PASS device as well as the electrical signal from

each of the thermocouples were connected to a 12 channel (Model CRX-23) or 70 channel

(Model CR-7) portable data acquisition system from Campbell Scientific Instruments. The 12

channel system was used for the static oven and flow loop experiments while the 70 channel

system was utilized in the field experiments. Both of these battery powered data collection

boxes recorded the PASS and thermocouple data at 2 s intervals. The software available with

the data acquisition system also allowed the temperatures and alarm status of the PASS devices

to be continuously monitored via a laptop computer.
16

IV. Results

For each of the tests, the response of a PASS device and the temperature were monitored

as a function of time. Five different models from four different manufacturers were included in

this study. The focus of this study was to help develop a standard test protocol for testing

thermal sensors, not to specifically evaluate the performance of any single PASS device. Each

model of PASS device was assigned an alphabetic letter as an identifier, such A, B, C, D, or E.

Since there were multiple devices of each model, the first device was assigned the number B-1

and the second B-2, and the third, B-3. Devices A through C included thermal sensors and

devices D and E did not include thermal sensors. The response and temperature data for the

laboratory tests are plotted versus time in Figures 13 - 15, and 16 - 18 for the static oven and

flow loop tests, respectively. For the full-scale tests, each PASS device response, temperature

and total heat flux are plotted in Figures 19 - 22.

A. Static Oven Tests

As shown in Figure 13 - 15, the each test was started with the temperature at less than

25 oC (77 oF). Over a period of time, ranging from 25 minutes to 60 minutes, the oven

temperature was gradually increased to 120 oC (250 oF). At temperatures above 120 oC (250

o

F), all the PASS devices began to emit odors that were suggestive of thermal decomposition and

since these PASS devices were also needed for flow tests and full scale tests, the static oven tests

were limited to 120 oC (250 oF) exposures. As the temperature inside the oven increased, the

PASS device would activate its alarm. For each test, alarm activation caused a change in the

analog signal from the PASS device. The corresponding gas or air temperature at the time of

this alarm activation was recorded as the alarm temperature. Each alarm activation was confirmed visually by the test operator who examined the LEDs on the front of each PASS device.

For PASS Device Model A, the average temperature (for each unit) at which the thermal

exposure sensor alarmed for three different units was 98 oC (210 oF) to 100 oC (212 oF).

Individual test alarm activations occurred between 88 oC (190 oF) and 105 oC (220 oF). As

shown in Figure 13, Model A-2 alarmed at 103 oC (217 oF) at 2170 s into the test. For PASS

Device Model B, the

average temperature at which the thermal exposure sensor alarmed for three different units was

82 oC (190 oF) to 98 oC (208 oF) which is slightly lower temperatures than for Model A.

Individual test alarm activations occurred between 81 oC (178 oF) and 98 oC (208 oF). As shown

in Figure 14, Model B-3 alarmed at 94 oC (201 oF) at 1880 s into the test. For PASS Device

Model C, the average temperature at which the thermal exposure sensor alarmed for three

different units was 93 oC (199 oF) to 110 oC (230 oF) which is slightly higher temperatures than

for Model A. Individual test alarm activations occurred between 80 oC (176 oF) and 122 oC

(252 oF) . As shown in Figure 15, Model C-2 alarmed at 90 oC (194 oF) at 2630 s into the test.

The static oven temperature versus response data for each of the PASS devices is included in

Table 1. Overall, the reproducibility between different PASS devices from the same

manufacture was relatively good. The range of alarm temperatures for Model A and Model B

was 17 oC (31 oF) and for all tests and all units. Model C exhibited a much larger variation in

temperatures with a range of 42 oC (76 oF). The greatest variation in alarm temperatures was

also exhibited by Model C devices.
17

0

20

40

60

80

100

120

0 500 1000 1500 2000 2500 3000

Air T

e

m

p

erature,

o

C

P

AS

S

A

n

alo

g

Sig

n

al

(arbitrary

v

olts)

Time, s

Air Temperature

at Alarm

Temperature

Sensor in Alarm

Figure 13. Static oven gas temperature versus PASS analog signal for device A-2.

Figure 14. Static oven gas temperature versus PASS analog signal for device B-3.

0

20

40

60

80

100

120

0 500 1000 1500 2000 2500

Air T

e

m

p

erature,

o

C

P

A

S

S

A

n

alo

g

Sig

n

al

(arbitrary

v

olts)

Time, s

Air Temperature

at Alarm

Temperature

Sensor in Alarm
18

0

20

40

60

80

100

120

0 500 1000 1500

Air Te

m

p

erature,

o

C

P

A

S

S

A

n

alo

g

Sig

n

al

(arbitrary

v

olts)

Time, s

Air Temperature

at Alarm

Temperature

Sensor in Alarm

Figure 15. Static oven gas temperature versus PASS analog signal for device C-2.

Figure 16. Flow loop gas temperature versus PASS analog signal for device A-1.

0

20

40

60

80

100

120

0 500 1000 1500 2000 2500 3000

Air T

e

m

p

erature,

o

C

P

A

S

S

A

n

alo

g

Sig

n

al

(arbitrary

v

olts)

Time, s

Air Temperature

at Alarm

Temperature

Sensor in Alarm
19

Table 1. Static oven exposure tests for PASS devices.

PASS

Device

Range of

Alarm

Temperature

Average

Alarm

Temperature

Number

of

Tests

89 oC – 105 oC

(192 oF – 221 oF)

99 oC

(210 oF)

4

93 oC – 105 oC

(199 oF – 221 oF)

100 oC

(212 oF)

3

Model A

A-1

A-2

A-3

88 oC – 105 oC

(190 oF – 221 oF)

98 oC

(208 oF)

4

81 oC – 98 oC

(178 oF – 208 oF)

87 oC

(189 oF)

4

82 oC – 93 oC

(187 oF – 199 oF)

88 oC

(190 oF)

5

Model B

B-1

B-2

B-3

86 oC – 97 oC

(187 oF – 207 oF)

92 oC

(198 oF)

4

109 oC – 114 oC

(228 oF – 237 oF)

110 oC

(230 oF)

3

87 oC – 98 oC

(189 oF – 208 oF)

93 oC

(199 oF)

2

Model C

C-1

C-2

C-3

80 oC – 122 oC

(176 oF – 252 oF)

98 oC

(208 oF)

5

B. Flow Loop Tests

As shown in Figure 16 - 18, the each test was started with the temperature at less than

25 oC (77 oF). Over a period of time, ranging from 30 minutes to 150 minutes, the loop air

temperature was gradually increased to 120 oC (250 oF). Because additional time was

necessary for the flow loop air temperature to stabilize after a step change, the duration of the

flow loop tests were significantly longer than for the static oven tests. As the temperature
20

Figure 17. Flow loop gas temperature versus PASS analog signal for device B-4.

Figure 18. Flow loop gas temperature versus PASS analog signal for device C-3.

0

20

40

60

80

100

120

0 1000 2000 3000 4000 5000 6000

Air T

e

m

p

erature,

o

CP

A

S

S

A

n

alo

g

Sig

n

al

(arbitrary

v

olts)

Time, s

Air Temperature

at Alarm

Temperature

Sensor in Alarm

0

20

40

60

80

100

120

0 2000 4000 6000 8000 10000

Air T

e

m

p

erature,

o

C

P

A

S

S

A

n

alo

g

Sig

n

al

(arbitrary

v

olts)

Time, s

Air Temperature

at Alarm

Temperature

Sensor in Alarm
21

inside the loop increased, the PASS device would activate its alarm. For each test, alarm

activation caused a change in the analog signal from the PASS device. The corresponding gas

or air temperature at the time of this alarm activation was recorded as the alarm temperature.

Each alarm activation was confirmed visually by the test operator by examining the LEDs on the

front of the device.

For PASS Device Model A, the average temperature (for each device) at which the

thermal exposure sensor alarmed for three different units was 47 oC (117 oF) to 58 oC (136 oF).

Individual test alarm activations occurred between 41 oC (106 oF) and 61 oC (142 oF). As shown

in Figure 16, Model A-1 alarmed at 59 oC (138 oF) at 1030 s into the test. For PASS Device

Model B, the average temperature at which the thermal exposure sensor alarmed for two

different units was 70 oC (158 oF) to 73 oC (163 oF) which is slightly higher temperatures than

for Model A. Individual test alarm activations occurred between 55 oC (131 oF) and 90 oC

(194 oF). As shown in Figure 17, Model B-4 alarmed at 90 oC (194 oF) at 4650 s into the test.

Table 2. Flow loop exposure tests for PASS devices.

PASS Device

Range of

Alarm

Temperatures

Average

Alarm

Temperature

Number of

Tests

50 oC - 61 oC

(122 oF - 142 oF)

56 oC

(133 oF)

4

58 oC

(136 oF)

58 oC

(136 oF)

1

Model A

A-1

A-2

A-3

41 oC - 50oC

(106 oF - 122 oF)

47 oC

(117 oF)

3

70oC

(158 oF)

70 oC

(158 oF)

1

Model B

B-2

B-4

55 oC - 90oC

(131 oF - 194 oF)

73 oC

(163 oF)

2

Model C

C-2

90 oC – 113 oC

(194 oF - 235 oF)

102

o

C

(216 oF)

4
22

For PASS Device Model C, the average temperature at which the thermal exposure

sensor alarmed for a single unit was 102 oC (216 oF) which is slightly higher temperatures than

for Model A or B. Individual test alarm activations occurred between 90 oC (194 oF) and 113 oC

(235 oF). As shown in Figure 18, Model C-3 alarmed at 113 oC (235 oF) at 8900 s into the test.

The flow loop temperature versus response data for each of the PASS devices is included in

Table 2. Overall, the reproducibility between different PASS devices from the same

manufacturer was not as good as for the static oven tests. The range of alarm temperatures for

Model A was 17 oC (31 oF) for all tests and all units. Model B demonstrated a wider range of

35 oC (63 oF) for the flow tests Model C exhibited a somewhat lower variation in temperatures

with a range of 23 oC (41 oF), but all four tests exposed the same PASS device, C-2. Model B-4

also exhibited the widest range alarm temperatures.

C. Full-Scale Mannequin Experiments

Data was collected from an instrumented mannequin that was exposed to realistic thermal

conditions during a series of townhouse field burns. The mannequin was positioned between the

kitchen and living room (Figure 12). An array of thermocouples was positioned next to the

mannequin to monitor gas temperatures from floor to ceiling. Two total heat flux gauges were

located next to the thermocouple array (Figures 8 and 12). One flux gauge was positioned

vertically (looking at the ceiling) in order to track the thermal radiation from the upper layer.

The other flux gauge was positioned horizontally (looking at the fire) to allow it to monitor the

thermal radiation from the initial fuel package. The flux gauge viewing the upper layer would

monitor the thermal flux that the shoulders and helmet might experience from the upper layer as

he/she knelt in a room containing an active fire. The flux gauge viewing the fuel package would

monitor the thermal flux that the front side of the fire fighter might experience as he/she faces

the fire. For Unit 1and Unit 2, 1 L (0.26 gal) of gasoline was poured on the center of the carpet

and ignited. Unit 3 was ignited using crumpled up newspaper in the corner of the sofa.

Gas temperatures, thermal sensor activation, and thermal heat fluxes for the full-scale test

in Unit 1 are plotted in Figures 19 - 24. For Unit 1, a thermocouple array from floor to ceiling

was 10 cm to the left of the mannequin’s left shoulder and had thermocouples located at

approximately 30 cm (12 in) intervals. The left shoulder of the turn-out gear on the mannequin

was 108 cm (42.5 in) above the floor and the centerline of the PASS devices was 95 cm (37.4 in)

above the floor. Peak temperature (room) for the gasoline fire in Unit 1 was approximately

181 oC ( 358 oF) at 200 cm ( 78.7 in) above the floor and was recorded at 260 s (Figure 19). The

total heat flux peaked at 30 kW/m2and 21 kW/m2for the horizontal and vertical gauges,

respectively (Figure 20). The horizontal or fuel package flux gauge reported higher values of

thermal flux earlier in the burn than the vertical flux gauge. This would be consistent with the

fire fighter experiencing most of the thermal radiation directly from the fire initially because the

upper layer requires additional time to form a hot layer of gases.

The analog signal from the thermal sensor and the temperatures for 200 cm (78.7 in),

110 cm (43.3 in), and 80 cm (31.5 in) above the floor are plotted in both Figures 21 and 22.

The 200 cm thermocouple tracked gas temperatures 30 cm (12 in) below the ceiling.
23

Figure 19. Gas temperatures versus time for full-scale townhouse burn in Unit 1.

Figure 20. Thermal heat flux versus time for full-scale townhouse burn in Unit 1.

0

50

100

150

200

250

300

0 100 200 300 400 500 600

Pinal County Test 1

230 cm (90.6 in) above floor (ceiling)

200 cm (78.7 in) above floor

170 cm (66.9 in) above floor

140 cm (55.1 in) above floor

110 cm (43.3 in) above floor

80 cm (31.5 in) above floor

50 cm (19.7 in) above floor

20 cm (7.9 in) above floor

T

e

m

p

erature,

oC

Time, s

0

10

20

30

40

50

0 100 200 300 400 500 600

Total Heat Flux - Vertical (gauge viewing upper layer)

Total Heat Flux - Horizontal (gauge viewing fuel package)

T

otal H

e

at Flu

x, k

W/m

2

Time, s
24

Figure 21. Gas temperature (room) versus thermal sensor activation for A model PASS devices

on front and rear of mannequin in Unit 1.

Figure 22. Gas temperature (room) versus thermal sensor activation for C model PASS devices

on front and rear of mannequin in Unit 1.

0

50

100

150

200

250

300

0 100 200 300 400 500 600

Temperature - 230 cm (90.6 in) above floor (at ceiling)

Temperature - 110 cm (43.3 in) above floor

Temperature - 80 cm (31.5 in) above floor

PASS A Front

PASS A Rear

T

e

m

p

erature,

oC

P

A

S

S

D

e

vic

e

Sig

n

al

(arbitrary

volts)

Time, s

0

50

100

150

200

250

300

0 100 200 300 400 500 600

Temperature - front of mannequin

Temperature - rear of mannequin

PASS C Front

PASS C Rear

Te

m

perature,

o

C

P

A

S

S

D

e

vic

e

Sig

n

al

(arbitrary

v

olts)

Time, s
25

Figure 23. Gas temperature (mannequin front and rear) and thermal sensor activation for model

A PASS devices in Unit 1.

Figure 24. Gas temperature (mannequin front and rear) and thermal sensor activation for model

C PASS devices in Unit 1.

0

50

100

150

200

250

300

0 100 200 300 400 500 600

Temperature - front of mannequin

Temperature - rear of mannequin

PASS A Front

PASS A Rear

T

e

m

p

erature,

oC

P

A

S

S

D

e

vic

e

Sig

n

al

(arbitrary

v

olts)

Time, s

0

50

100

150

200

250

300

0 100 200 300 400 500 600

Temperature - front of mannequin

Temperature - rear of mannequin

PASS C Front

PASS C Rear

T

e

m

p

erature,

o

C

P

A

S

S

D

e

vic

e

Sig

n

al

(arbitrary

v

olts)

Time, s
26

The 110 cm thermocouple was 2 cm (1 in) above the left shoulder and the thermocouple at 80 cm

was 15 cm (6 in) below the PASS devices. PASS devices were positioned on the front and rear

of the mannequin. The thermal environment of this burn did not cause any of the four PASS

devices, front or rear to activate during this test (Figure 21 and 22). The peak temperature

(room), time of peak at which the peak temperature (room) occurred, and the alarm activation

time are tabulated in Table 3. In a similar manner the analog signal from the thermal sensor and

the temperatures for front and rear of the mannequin near each PASS device are plotted in both

Figures 23 and 24. The peak temperature (mannequin front and rear), time of peak at which the

peak temperature (front and rear) occurred, and the alarm activation time are tabulated in

Table 4.

Gas temperatures, thermal sensor activation, and thermal heat fluxes for the full-scale test

in Unit 2 are plotted in Figures 25 - 30. For Unit 2, a thermocouple array from floor to ceiling

was 10 cm to the left of the mannequin’s left shoulder and had thermocouples located at

approximately 30 cm (12 in) intervals. The left shoulder of the turn-out gear on the mannequin

was 108 cm (42.5 in) above the floor and the centerline of the PASS devices was 95 cm (37.4 in)

above the floor. Peak temperature (room) for the fire in Unit 2 was 306 oC ( 583

o

F) at 200 cm

(78.7 in) above the floor and was recorded at approximately 410 s (Figure 25). The total heat

flux peaked at 97 kW/m2and 70 kW/m2for the horizontal and vertical gauges, respectively

(Figure 26). The peak heat flux was much greater in Unit 2 than for Unit 1, however, the peak in

Unit 2 is observed later as the additional fuel, including the sofa and chair, become involved in

the fire. Early in the burn at about 210 s, the vertical heat flux reaches a level of 40 kW/m2

which is similar in magnitude to the peak heat flux in Unit 1. This would be consistent with

each of the fires in Unit 1 and 2 being initiated with 1 L (0.26 gal) of gasoline. However, it

should be noted that in Unit 1, the horizontal heat flux reached about 30 kW/m2while in Unit 2 it

was the vertical component of heat flux which reached 40 kW/m2.

The analog signal from the thermal sensor and the temperatures for 200 cm (78.7 in),

110 cm (43.3 in), and 80 cm (31.5 in) above the floor are plotted in both Figures 27 and 28.

The 200 cm thermocouple tracked gas temperatures 30 cm (12 in) below the ceiling. The

110 cm thermocouple was 2 cm (1 in) above the left shoulder and the thermocouple at 80 cm was

15 cm (6 in) below the PASS devices. PASS devices were positioned on the front and rear of

the mannequin. The peak temperature (room) of 306 oC (583 oF) was reached at 410 s and only

the rear mounted PASS devices activated during the fire in Unit 2. Model A-1 activated at 530 s

(Figure 27) and Model C-3 alarmed at 485 s (Figure 28). The time between peak exposure

(room) and thermal sensor activation was 120 s and 75 s for A-1 and C-3, respectively. In a

similar manner the analog signal from the thermal sensor and the temperatures for front and rear

of the mannequin near each PASS device are plotted in both Figures 29 and 30. The peak

temperature (mannequin front and rear), time of peak at which the peak temperature (front and

rear) occurred, and the alarm activation time are tabulated in Table 4.

Gas temperatures, thermal sensor activation, and thermal heat fluxes for the full-scale test

in Unit 3 are plotted in Figures 31 - 36. For Unit 3, a thermocouple array from floor to ceiling

was 10 cm to the left of the mannequin’s left shoulder and had thermocouples located at

approximately 30 cm (12 in) intervals. The left shoulder of the turn-out gear on the mannequin

was 108 cm (42.5 in) above the floor and the centerline of the PASS devices was 95 cm (37.4 in)

above the floor. Peak temperature for the fire in Unit 3 was 631 oC (1168 oF) at 200 cm

(78.7 in) above the floor and was recorded at approximately 305 s (Figure 31). The total heat
27

flux peaked at 150 kW/m2and 130 kW/m2for the horizontal and vertical gauges, respectively

(Figure 32). The peak heat flux was much greater in Unit 3 than for Unit 1 or 2. The early rapid

rise in heat flux that was observed in Unit 1 and 2 is missing in Unit 3, but Unit 3 was initiated

by igniting a crumpled newspaper, not the gasoline as in Unit 1 and 2.

The analog signal from the thermal sensor and the temperatures for 200 cm (78.7 in),

110 cm (43.3 in), and 80 cm (31.5 in) above the floor are plotted in both Figures 33 and 34.

The 200 cm thermocouple tracked gas temperatures 30 cm (12 in) below the ceiling. The

110 cm thermocouple was 2 cm (1 in) above the left shoulder and the thermocouple at 80 cm was

15 cm (6 in) below the PASS devices. PASS devices were positioned on the front and rear of

the mannequin. The peak temperature (room) of 631 oC (1168 oF) was reached at 305 s and the

thermal sensors for all four of the PASS devices activated. Two Model A PASS devices were

mounted on the mannequin, A-3 on the front and A-1 on the rear. The thermal sensors activated

at 330 s and 385 s for the front and rear, respectively (Figure 33). Two Model C PASS devices

were also mounted on the mannequin, one on the front and one on the rear. While the front

mounted C-4 PASS activated at 340 s, the C-3 device on the rear of the mannequin activated at

365 s (Figure 34). The times between peak exposure (room) and thermal sensor activation for

the front of the mannequin were 25 s and 35 s for A-3 and C-4, respectively. The times between

peak exposure (room) to activation for the rear of the mannequin were significantly longer at

80 s and 60 s for A-1 and C-3, respectively. In a similar manner the analog signal from the

thermal sensor and the temperatures for front and rear of the mannequin near each PASS device

are plotted in both Figures 35 and 36. The peak temperature (mannequin front and rear), time

of peak at which the peak temperature (front and rear) occurred, and the alarm activation time

are tabulated in Table 4.

D. Uncertainty Analysis

There are different components of uncertainty in the temperatures, total heat flux, and

time to activate data reported here. Uncertainties are grouped into two categories according to

the method used to estimate them. Type A uncertainties are evaluated by statistical methods, and

Type B are evaluated by other means [9]. 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 percent. After

estimating uncertainties by either Type A or B analysis, the uncertainties are combined in

quadrature to yield the combined standard uncertainty. Multiplying the combined standard

uncertainty by a coverage factor of two results in the total expanded uncertainty that corresponds

to a 95 percent confidence interval (2F).

Components of uncertainty are tabulated in Tables 5 and 6. Some of these components,

such as the zero and calibration elements, are derived from instrument specifications. Other

components, such as soot deposition or radiative cooling/heating include past experience with

thermophoretic deposition on cool surfaces and thermocouples in high temperature fuel rich

environments. The uncertainty in the air temperature measurements includes radiative cooling in

the each of the tests series, but also includes radiative heating for thermocouple located in the

lower layer of the full-scale tests. This resulted in an estimate of -23 % to +12 % total

expanded uncertainty for the lab tests and a slightly larger estimate of –32 % to +15 % for the
28

Table 3. Full-scale townhouse exposure tests for PASS devices (room peak temperatures).

Configuration &

Fuel Package

Peak

Temperature

(room)

Time of

Peak

Temperature

(room)

PASS

Device

ID

PASS

Location

Time of

Activation

Peak

Exposure to

Activation

A-3 Front Did not

Activate

Did Not

Activate

A-1 Rear Did not

Activate

Did Not

Activate

C-4 Front Did not

Activate

Did Not

Activate

Unit 1

Unfurnished

Living Room

Carpeting

Gasoline

Ignition

181 oC

(358 oF)

182 s

C-3 Rear Did not

Activate

Did Not

Activate

A-3 Front Did not

Activate

Did Not

Activate

A-1 Rear 530 s 120 s

C-4 Front Did not

Activate

Did Not

Activate

Unit 2

Furnished Living

Room

Carpeting, Sofa,

Chair, End table

Gasoline

Ignition

306 oC

(583 oF)

410 s

C-3 Rear 485 s 75 s

A-3 Front 330 s 25 s

A-1 Rear 385 s 80 s

C-4 Front 340 s 35 s

Unit 3

Furnished Living

Room

Carpeting, Sofa,

Chair, End table

Newspaper

Ignition

631 oC

(1168 oF)

305 s

C-3 Rear 365 s 60 s
29

Table 4. Full-scale townhouse exposure tests for PASS devices (mannequin peak temperatures).

Configuration &

Fuel Package

PASS

Device

ID

PASS

Location

Peak

Temperature

(mannequin)

Time of Peak

Temperature

(mannequin)

Time of

Activation

Peak

Exposure to

Activation

A-3 Front 107 oC

(225 oF)

295 s Did not

Activate

Did Not

Activate

A-1 Rear 109 o

C

(228 oF)

290 s Did not

Activate

Did Not

Activate

C-4 Front 101 oC

(214 oF)

285 s Did not

Activate

Did Not

Activate

Unit 1

Unfurnished

Living Room

Carpeting

Gasoline

Ignition

C-3 Rear 118 oC

(244 oF)

290 s Did not

Activate

Did Not

Activate

A-3 Front 154 o

C

(309 oF)

420 s Did not

Activate

Did Not

Activate

A-1 Rear 158 o

C

(316 oF)

420 s 530 s 110 s

C-4 Front 169 oC

(336 oF)

420 s Did not

Activate

Did Not

Activate

Unit 2

Furnished Living

Room

Carpeting, Sofa,

Chair, End table

Gasoline

Ignition

C-3 Rear 182 oC

(360 oF)

420s 485 s 65 s

A-3 Front 261 o

C

(502 oF)

305 s 330 s 25 s

A-1 Rear 245 oC

(489 oF)

310 s 385 s 75 s

C-4 Front 266 oC

(511 oF)

305 s 340 s 35 s

Unit 3

Furnished Living

Room

Carpeting, Sofa,

Chair, End table

Newspaper

Ignition

C-3 Rear 265 oC

(509 oF)

310 s 365 s 55 s
30

Figure 25. Gas temperatures versus time for full-scale townhouse burn in Unit 2.

Figure 26. Thermal heat flux versus time for full-scale townhouse burn in Unit 2.

0

50

100

150

200

250

300

350

400

0 100 200 300 400 500 600

Pinal County Test 1

230 cm (90.6 in) above floor (ceiling)

200 cm (78.7 in) above floor

170 cm (66.9 in) above floor

140 cm (55.1 in) above floor

110 cm (43.3 in) above floor

80 cm (31.5 in) above floor

50 cm (19.7 in) above floor

20 cm (7.9 in) above floor

T

e

m

p

erature,

o

C

Time, s

0

50

100

150

200

0 100 200 300 400 500 600

Total Heat Flux - Vertical (gauge viewing upper layer)

Total Heat Flux - Horizontal (gauge viewing fuel package)

T

otal H

e

at Flu

x, kW/m2

Time, s
31

Figure 27. Temperature (room) and thermal sensor activation for PASS device A in Unit 2.

Figure 28. Temperature (room) and thermal sensor activation for PASS device C in Unit 2

0

100

200

300

400

500

0 100 200 300 400 500 600

Temperature - 230 cm (90.6 in) above floor (at ceiling)

Temperature - 110 cm (43.3 in) above floor

Temperature - 80 cm (31.5 in) above floor

PASS A Front

PASS A Rear

T

e

m

p

erature,

oC

P

A

S

S

D

e

vic

e

Sig

n

al

(arbitrary volts)

Time, s

0

100

200

300

400

500

0 100 200 300 400 500 600

Temperature - 230 cm (90.6 in) above floor (at ceiling)

Temperature - 110 cm (43.3 in) above floor

Temperature - 80 cm (31.5 in) above floor

PASS C Front

PASS C Rear

Te

m

p

erature,

o

C

P

AS

S

De

vic

e

Sig

n

al

(arbitrary volts)

Time, s
32

Figure 29. Temperature (mannequin front and rear) and thermal sensor activation for PASS

device A in Unit 2

Figure 30. Temperature (mannequin front and rear) and thermal sensor activation for PASS

device C in Unit 2

0

100

200

300

400

500

0 100 200 300 400 500 600

Temperature - front of mannequin

Temperature - rear of mannequin

PASS A Front

PASS A Rear

Te

m

p

erature,

o

C

P

A

S

S

D

e

vic

e

Sig

n

al

(arbitrary volts)

Time, s

0

100

200

300

400

500

0 100 200 300 400 500 600

Temperature - front of mannequin

Temperature - rear of mannequin

PASS C Front

PASS C Rear

T

e

m

perature,

o

C

P

A

S

S

D

e

vic

e

Sig

n

al

(arbitrary volts)

Time, s
33

Figure 31. Gas temperatures versus time for full-scale townhouse burn in Unit 3.

Figure 32. Thermal heat flux versus time for full-scale townhouse burn in Unit 3.

0

50

100

150

200

250

300

0 100 200 300 400 500 600

Pinal County Test 1

230 cm (90.6 in) above floor (ceiling)

200 cm (78.7 in) above floor

170 cm (66.9 in) above floor

140 cm (55.1 in) above floor

110 cm (43.3 in) above floor

80 cm (31.5 in) above floor

50 cm (19.7 in) above floor

20 cm (7.9 in) above floor

T

e

m

p

erature,

oC

Time, s

0

50

100

150

200

0 100 200 300 400 500 600

Total Heat Flux - Vertical (gauge viewing upper layer)

Total Heat Flux - Horizontal (gauge viewing fuel package)

Total H

e

at Flu

x, kW/m

2

Time, s
34

Figure 33. Temperature (room) and thermal sensor activation for PASS device A in Unit 3.

Figure 34. Temperature (room) and thermal sensor activation for PASS device C in Unit 3.

0

100

200

300

400

500

600

700

0 100 200 300 400 500 600

Temperature - 230 cm (90.6 in) above floor (at ceiling)

Temperature - 110 cm (43.3 in) above floor

Temperature - 80 cm (31.5 in) above floor

PASS A Front

PASS A Rear

T

e

m

p

erature,

o

C

P

A

S

S

D

e

vic

e

Sig

n

al

(arbitrary volts)

Time, s

0

100

200

300

400

500

600

700

0 100 200 300 400 500 600

Temperature - 230 cm (90.6 in) above floor (at ceiling)

Temperature - 110 cm (43.3 in) above floor

Temperature - 80 cm (31.5 in) above floor

PASS C Front

PASS C Rear

Te

m

p

erature,

oC

P

A

S

S

D

e

vic

e

Sig

n

al

(arbitrary volts)

Time, s
35

Figure 35. Temperature (mannequin front and rear) and thermal sensor activation for PASS

device A in Unit 3.

Figure 36. Temperature (mannequin front and rear) and thermal sensor activation for PASS

device C in Unit 3.

0

100

200

300

400

500

0 100 200 300 400 500 600

Temperature - front of mannequin

Temperature - rear of mannequin

PASS A Front

PASS A Rear

T

e

m

perature,

oC

P

A

S

S

D

e

vic

e

Sig

n

al

(arbitrary

v

olts)

Time, s

0

100

200

300

400

500

0 100 200 300 400 500 600

Temperature - front of mannequin

Temperature - rear of mannequin

PASS C Front

PASS C Rear

Te

m

perature,

oC

P

A

S

S

D

e

vic

e

Sig

n

al

(arbitrary

v

olts)

Time, s
36

full scale tests. Soot deposition on the face of the water-cooled total heat flux gauges contributed

significant uncertainty to the heat flux measurements. Calibration of heat flux gauges was

completed at lower fluxes and then extrapolated to higher values and this resulted in a higher

uncertainty in the flux measurement. Combining all of component uncertainties for total heat

flux resulted in a total expanded uncertainty of – 31% to + 23 % for the flux measurements.

Estimating the uncertainty in the activation temperature for the static oven and flow loop

experiments required the uncertainties in air temperature, alarm activation, and repeatability to

generate a total expanded uncertainty range of –32 % to +26 %. For the full-scale experiments,

the total expanded uncertainty in peak exposure to alarm activation time measurements was

estimated to range between – 15 % and + 18 %. In all the experimental test series, positioning

or locating instrumentation such as thermocouples or heat flux gauges was estimated to have the

lowest total expanded uncertainty of ± 11 %.

Table 5. Uncertainty in static oven and flow loop experimental data.

Component

Standard

Uncertainty

Combined

Standard

Uncertainty

Total

Expanded

Uncertainty

Air Temperature

Calibration

Radiative Cooling

Repeatability 1

Random 1

± 1 %

- 10% to + 0 %

± 5 %

± 3 %

- 12 % to + 6 % - 23 % to + 12 %

Activation Temperature2

Air Temperature

Alarm Activation

Repeatability 1

Random 1

- 12 % to + 6 %

- 0 % to + 5 %

± 10 %

± 3 %

- 16 % to + 13 % - 32 % to + 26 %

Instrument Location

Zero

Repeatability 1

Random 1

± 1 %

± 5 %

± 2 %

± 5 % ± 11 %

Notes: 1. Random and repeatability evaluated as Type A, other components as Type B.

2. Determined from intersection of oven temperature and PASS alarm signal data when plotted

versus time on a single graph.
37

Table 6. Uncertainty in full scale experimental data.

Component

Standard

Uncertainty

Combined

Standard

Uncertainty

Total

Expanded

Uncertainty

Air Temperature

Calibration

Radiative Cooling

Radiative Heating

Repeatability 1

Random 1

± 1 %

- 15 % to + 0 %

- 0 % to + 5 %

± 5 %

± 3 %

- 16 % to + 8 % - 32 % to + 15 %

Total Heat Flux

Calibration

Zero

Soot Deposition

Repeatability 1

Random 1

± 10 %

- 2 % to + 2 %

- 10% to + 0 %

± 5 %

± 3 %

- 15 % to + 12 % - 31 % to + 23 %

Peak Exposure to

Activation Time 2

Time of Peak

Alarm Activation

Repeatability 1

Random 1

± 5 %

-0 % to + 5 %

± 5 %

± 3 %

- 8 % to + 9 % - 15 % to + 18 %

Instrument Location

Zero

Repeatability 1

Random 1

± 1 %

± 5 %

± 2 %

± 5 % ± 11 %

Notes: 1. Random and repeatability evaluated as Type A, other components as Type B.

2. Peak Exposure to Activation Time - time between exposure to peak temperature near

PASS device and time of thermal sensor activation.
38

V. Discussion

A. Thermal Exposure Sensor Activation

This study has examined the performance of thermal exposure sensor equipped PASS

devices to the different thermal environments that fire fighters experience on the fire ground.

The static oven tests were designed to simulate fire fighter activity is a layer of stagnant hot

gases. The flow loop exposures were intended to reproduce a fire fighter’s motion through hot

gases or the movement of hot combustion gases around a stationary fire fighter. And, the fullscale fire tests exposed the PASS instrumented mannequin to typical fire conditions. For each of

these scenarios, the gas temperature and alarm activation was observed for each PASS device.

Static Oven and Flow Loop Test Series

This limited set of temperature versus alarm activation data demonstrates average alarm

temperatures of between 87 oC (189 oF) and 110 oC (230 oF) for all the PASS devices (Table 1).

This series of tests reveals that different models can respond differently to static smoke

conditions. Model B PASS devices displayed the lowest average activation temperatures while

Model C revealed the highest average activation temperatures. Alarm activation repeatability

appears good for Model A and B. Model C unit C-3 exhibited a wider range of alarm activation

temperatures than any other PASS tested. Activation temperature is influenced by many factors

including, but not limited to sensor type, sensor position, and how the temperature is processed

by the circuitry of the PASS device. This limited data set does not demonstrate which factor or

factors are responsible for generating the range of activation temperatures. There are

significant uncertainties (Table 5) associated with the measurements and the range of total

expanded uncertainties is larger than the range of temperatures measured.

The smaller series of flow loop tests produced much lower activation temperatures than

observed in the static oven tests. This would be consistent with the heated air flow being able to

transfer thermal energy to the PASS device more effectively than the static oven. The flow loop

experiments generated wider range of activation temperatures than for the static oven tests. The

thermal exposure sensors exhibited average alarm temperatures from 54 oC (129 oF), 72 oC

(162 oF), to 102 oC (216 oF) for Models A, B, and C, respectively. Model A activated over a

narrower range than Models B and C. On average, Model A alarmed at a much lower

temperature than Model B or C. Even though this is a limited data set, the activation

temperatures indicate that the thermal sensors respond differently to moving or flowing smoke

than to static or quiescent smoke. Would the lower response temperatures display by Model A

provide additional warning to fire fighters or would the lower activation temperatures generate

unwanted false alarms?

Comparing the static oven and the flow loop alarm temperatures suggests that the thermal

sensor utilized by Model A is more sensitive to the convective component of heat transfer

associated with the flow loop. Model B also appears to respond to the convective component of

heat transfer, but to a lesser degree than Model A. Model C activated at similar temperatures for

both the static oven and the flow loop tests.

While each PASS device experienced similar exposures to the thermal environment of

the static oven or flow loop series, additional experiments would be necessary to map out the

entire temperature versus alarm response curve as a function of time. For example, this
39

experimental data set would not have captured an alarm activation resulting from a 60 minute

exposure to 50 oC (122 oF) environment. In a similar fashion, it might be useful to expose each

PASS device to much higher temperatures, such as 400 oC (752 oF) for short durations.

However, the high temperature/short durations would probably cause irreversible damage to the

PASS device. The high temperature endurance of the thermal exposure sensors, in terms of the

total duration or number of trips into high temperature conditions, would also be useful

information in determining when PASS devices should be replaced.

Full-Scale Mannequin Experimental Series

The response of the PASS devices during the townhouse burns initially appears to be

inconsistent. In the Unit 1 fire test, none of the thermal sensors activated during the burn. In

Unit 2, the rear PASS devices, A-1 and C3, both alarmed but the front PASS devices, A-3 and

C-4, did not alarm. In the Unit 3, both front PASS devices alarm before the rear PASS devices

alarm. However, with more detailed examination of the gas temperatures and total heat fluxes,

the thermal sensor activations are relatively consistent. Each of the fires in Unit 1 and Unit 2

was initiated by igniting gasoline, so both fire developed quickly, but the fuel in Unit 1 was

limited to carpeting, no furniture. The fire in Unit 1 started quickly, but after consuming the

gasoline, the fire began to decrease in its intensity. Initially the gasoline fueled fire generated

significant levels of thermal radiation to help pyrolyze additional fuel, but as the gasoline was

expended, the carpeting continued to burn, but the line of flames was distributed over a wider

flame front and this would have reduced the radiation feedback to the fuel. The reduced

feedback would have caused the fire to decrease in it intensity. The fire in Unit 2 also started

quickly, but there was additional furniture in the living room. Consequently, the temperature

data show the same initial development and actually begin to decline. But as the fire spreads to

additional items, the intensity of the fire increases until the fire begins to approach flashover and

suppression was initiated. The fire in Unit 3 was slower to develop initially because it was

ignited with crumpled newspaper rather than gasoline. The crumpled newspaper was positioned

on the sofa and may have caused the fire to spread more quickly across the sofa and chair. The

gasoline was spilled in the center of the carpet and the fire at least in the initial stages, was a

greater distance from the additional fuel items. The higher temperatures and heat fluxes

observed in Unit 3 suggest that more of the fuel package became involved in the early stages of

the fire than in Unit 2. As a result of more of the furnishings becoming involved, the intensity

of the fire in Unit 3 fire increased until the fire approached flashover and water suppression was

initiated.

As one would expect, the intensity of the fire in Unit 3 produced the highest gas

temperatures and the highest thermal heat fluxes while Unit 1 reported the lowest temperatures

and heat fluxes. It would be consistent to find that the fire in Unit 3 activated all of the thermal

sensors, front and rear of the mannequin, while none of the thermal sensors activated in Unit 1.

This indicates that the temperatures/fluxes were sufficient in Unit 3, and not sufficient to cause

activation in Unit 1. In Unit 2, the fire produced temperatures and fluxes in between those

observed in Unit 1 (lower than Unit 2) and Unit 3 (higher than Unit 2). Consequently, it should

not be a surprise that only two out of the four thermal sensor equipped PASS devices alarmed in

Unit 2. It is curious that it was not the two PASS devices on the front of the mannequin which

faced the burning fuel package. It was the two PASS devices on the rear of the mannequin that

activated. Since the PASS devices on the front and rear of the mannequin would experience the
40

radiation from the hot upper layer, one might expect that the additional thermal flux from the

burning fuel package that only the PASS devices facing the fire would experience would cause

the front PASS devices to activate first. However, the rear-mounted devices activated first and

those PASS devices would have been shielded by the body of the mannequin from the radiation

of the burning fuel. But, the activation of the rear thermal sensors demonstrates that the rear of

the mannequin may have experienced some additional energy that did not impact the PASS

devices on the front. One possibility is that as the hot layer moved across the ceiling and struck

the rear wall of the townhouse, some portions of the hot layer may have recirculated or moved

down the wall and towards the rear of the mannequin. If this “reflected jet” of hot upper layer

gases was sufficiently strong, it may have convected additional thermal energy to the rear of the

mannequin. The mannequin would have shielded the front mounted devices from this reflected

stream of hot gases. This would suggest that the energy convected by the reflected stream to the

rear devices was greater than the radiative energy received by the front PASS devices.

Modeling this set of experiments using computer fire models such as fire Dynamic Simulator

[10] could provide additional insight about the recirculation the hot combustion gases around the

mannequin.

While the activation of the rear mounted PASS devices in Unit 2 may suggest that the

radiation from the burning fuel package was not sufficient to activate the thermal sensors on the

front of the mannequin, the heat flux reached much higher levels in Unit 3 and the combination

of gas temperatures did activate all four of the thermal sensor equipped PASS devices in Unit 3.

But, the two front mounted devices activated much more quickly than the rear mounted devices

and this would be consistent with radiative heat flux playing a role in the activation. There were

also significant delays between the activation of the front PASS devices and the rear PASS

devices. The time between peak temperature and thermal sensor activation was tabulated for

both peak room temperature and peak temperature near each PASS device. It did not appear to

make much difference whether the time was calculated from the peak room temperature or the

peak mannequin temperature. The peak exposure to alarm activation time was significantly

longer, 65 s to 120 s, for the mannequin in Unit 2 as compared to Unit 3 which had a range of

25 s to 80 s. The longer exposure to activation time in Unit 2 would be consistent with a less

intense fire development while the shorter times in Unit 3 would reflect the more intense

temperature and heat flux environment. The full-scale townhouse burns demonstrate that

thermal radiation can significantly affect the activation of the thermal exposure sensor, but

clearly illustrate that conduction, convection and radiation can work in different combinations to

cause a thermal sensor to alarm.

Since a fire fighter may be exposed to relatively low temperature environments such as

the fire in Unit 1, it is important that a standard testing protocol include a component that

simulates the exposure of the thermal sensor to a relative low temperature, less than 70 oC

(158 oF), for a relatively long period of time, up 30 minutes. When the static oven activation

temperatures are compared to the flow loop temperatures, it is clear that the testing protocol also

needs to include a component with the hot gases moving across the fire fighter. The importance

of moving or recirculating gases was also observed in the activation of the rear mounted PASS

devices in Unit 2. The full-scale results illustrate the role that thermal radiation can play in

thermal sensor activation and the standard protocol should also include exposure to thermal

radiation. Although limited, the static oven, flow loop, and full-scale test data, all indicate that
41

a thermal sensor must be characterized under conductive, convective, and radiative modes of

heat transfer.

This limited data set also raises some additional issues associated with thermal sensors in

PASS devices. Each thermal sensor is designed to activate according to a temperature response

curve. The higher the temperature, the quicker the thermal sensor is designed to activate. But,

in the full-scale townhouse tests, there was between 25 s and 120 s delay between peak exposure

and sensor activation. If a fire fighter had delayed their retreat until the thermal sensor had

activated, up to 2 minutes, serious injury could have occurred. If the thermal sensor in PASS

devices is intended to warn the fire fighter of a possibly hazardous thermal environment, the

PASS device must provide this warning quickly, not 60 s or 90 s later. A thermal sensor can be

designed to activate in response to a range of parameters. Sensors can activate when a specific

temperature is exceeded. This type of sensor might be set to alarm when a temperature greater

than 100 oC (212 oF) is experienced. The sampling frequency of a sensor can also impact how

quickly it alarms. If a sensor only looks at the temperature every 30 s, the temperature may

exceed the set point for up to 30 s before the alarm is activated. A temperature specific sensor

might alarm at the sudden rise in temperature, but a prolonged exposure to temperatures just

below the set point, say 2 hours at 98 oC (209 oF) might not trigger an alarm. A thermal sensor

can also be designed to activate when the sensor has experienced a certain amount of energy.

This type of sensor would accumulate or integrate the energy and when sufficient energy had

been collected, it would alarm. An integrating type sensor would alarm whether that energy

arrived in a few seconds or over an hour, but the process of accumulating the energy could slow

how fast the alarm is activated. A sensor can also be designed to alarm at a certain rate of

temperature increase. A rate of rise sensor would activate when the temperature is increasing

faster than a specific rate. For instance, if alarm set point was 50 oC (90 oF) per second, a

temperature that increased from 100 oC (212 oF) to 200 oC (392 oF) in less than a second would

trigger an alarm. Different fire conditions would cause each of these different sensor designs to

alarm. A rate of rise sensor would not alarm under the thermal conditions, relatively low

temperatures over a period of time, that occurred in Unit 1. A temperature specific or integrating

sensor may not respond quickly enough to warn of the hazardous conditions, rapidly rising

temperature, in Unit 2 or 3. A thermal sensor may have to incorporate the ability to alarm to

multiple conditions, rapid temperature rise over a short period of time as well as lower

temperatures over a prolonged period of time. The full-scale townhouse data clearly suggests

that the thermal sensors mounted on the front and rear of the mannequin did not provide

sufficient warning to allow safe retreat from the fire conditions. These PASS thermal sensors

may provide information on the integrated or total exposure to thermal conditions which could

be used by the incident commander to reassign the affected fire fighters to rehab. But, this

limited data indicates that fire fighters should not rely on current thermal sensors to provide

adequate warning of short-term exposures to the hazards of high thermal radiation or high

temperature environments.

A second issue that the full-scale data highlights is the position or location of the thermal

sensor on the fire fighter. In the Unit 3 tests, the body of the mannequin shielded the rearmounted PASS devices from the thermal radiation of the burning fuel package. In Unit 2, the

body of mannequin may have shielded the front mounted PASS devices from the recirculation

zone that may have occurred behind the mannequin. If a single thermal sensor is utilized,

neither the front or rear location will adequately address the issue of the sensor being shielded by
42

the body of the fire fighter. Either multiple point sensing, front and rear, or another location on

the fire fighter may needed to be considered. Multiple point sensing would monitor the

temperature at different locations and would alarm if the set point temperature is exceeded on

either front or rear location. Mounting the thermal sensor on the shoulder or on the helmet may

provide a compromise that minimizes the ability of the body to shield the thermal sensor. Front

or rear mounted thermal sensors do not appear to provide optimum coverage and alternatives

need to be investigated.

B. Standard Test Protocol

The thermal exposure sensor response data collected by this study demonstrates that

current sensors respond differently to different fire conditions. Thermal exposures can be for

short periods at high temperatures or for prolonged periods at lower temperatures. For both of

these exposures, acute and prolonged, thermal exposure sensors are expected to provide adequate

warning of hazardous thermal environments. A well-designed testing protocol must

characterize the thermal sensor performance when immersed in stagnant hot gases, enveloped by

moving combustion products, and experiencing intense thermal radiation. The testing protocol

should at a minimum include components to collect response versus temperature data for thermal

sensors encountering the following fire scenarios:

A) Quiescent hot gases for temperature ranging from 150 oC (300 oF) to 300 oC (572 oF),

for prolonged and acute exposures respectively; recommend using static oven to

evaluate this condition,

B) Flowing or moving hot gases for temperature ranging from 125 oC (260 oF) to 250 oC

(482 oF) for prolonged and acute exposures respectively; with gas velocity ranging

from 0.22 m/s (0.5 mph) to 2.24 m/s (5 mph); recommend employing a flow loop that

allows for variable temperature and velocity.

C) High thermal flux / pre-flashover conditions with total heat fluxes from 2.5 kW/m2to

30 kW/m2for prolonged and acute exposures respectively; recommend either electric

resistance radiant panel or gas fired radiant panel.

While the test protocol needs to include these scenarios, the protocol should not be used

to limit the characterization of thermal sensor performance to only these three scenarios. For

example, it is important that a temperature response curve describe the thermal sensor

performance over a wider range of temperatures from 25 oC (77 oF) to 600 oC (1112 oF).

As the standard testing protocol is developed, it must also address whether the thermal

sensor is designed to provide warning of an imminent hazard, such as rapid increase in

temperature just before flashover, or designed to alarm after a more prolonged exposure to

relatively lower temperatures. If the alarm is intended to provide time to retreat safely from an

imminent hazard, then the alarm activation must occur almost instantaneously when the sensor

experiences either the imminent hazard or the conditions leading to an imminent hazard. The

time delay must be on the order of seconds, not minutes. If the alarm is expected to warn of an
43

exposure over an extended period of time, then the time between exposure and alarm can be

substantially longer.

A draft protocol for Thermal Exposure Sensor is described in Appendix A. It includes sections

that address A) Design Requirements, B) Performance Requirements, and C) Test Methods.

The draft protocol incorporates

1) Exposure temperatures and durations for each of the above three scenarios,

2) Tests on fully assembled, ready for service, PASS devices,

3) Pre-test conditioning of specimens,

4) Testing of multiple units of the same model of PASS device,

5) Specific velocities for moving gases,

6) Non-destructive testing at low temperatures,

7) Destructive testing at high temperatures,

8) Data to be recorded during each test,

9) Interpretation of results.

It is critically important that input from the fire service, the PASS manufacturers, testing

laboratories, and fire research institutions be included in the development of the standard testing

protocol. The fire service will provide insight into the conditions and thermal environments that

fire fighters experience. Manufacturers will continue to incorporate new technologies to provide

improved instrumentation for fire fighter safety. Fire testing laboratories will make sure that the

performance can be adequately characterized. Research institutions will help ensure a scientific

foundation for the design and help identify new technology for future devices.

VI. Conclusions

The limited set of temperature versus thermal sensor activation data indicates that sensors

respond differently under static, flowing, and radiation intense conditions. The full-scale data

demonstrate that current thermal sensing/PASS implementations are unlikely to provide a fire

fighter with sufficient warning of an acute thermal hazard. Current PASS devices may provide

information to fire fighters about their longer term exposure to thermal conditions, but there is a

significant delay of 25 s to 120 s before the fire fighter receives this alarm or information.

This limited series of experiments demonstrates the need to develop a standard testing

protocol to insure that all PASS devices provide adequate protection for fire fighters. This

testing protocol must evaluate the performance of thermal sensors under a range of fire

environments that fire fighters may realistically encounter on a routine basis. The fire service,

equipment manufacturers, and fire research and fire testing laboratories must be included in the

development of a standard testing protocol.

The overall goal of this work is to improve the safety and effectiveness of fire fighters.

To accomplish this goal, the fire service must be able to incorporate state-of-the-art technology

into all of its equipment. But, in order for the fire service to integrate new technology safely, it

must be able to understand the performance and the limitations of this new technology.
44

VII. Acknowledgements

This project was funded by the US Fire Administration, Federal Emergency Management

Agency with Mr. William Troup served as project officer. Mr. Jack Lee and Mr. Roy McLane

expertly conducted both static oven and flow loop experiments. Mr. Robert Vettori and Mr. Jay

McElroy did an excellent job of field instrumentation and mannequin setup.

VIII. References

1. Karter, M.J., Jr., “Patterns of Firefighter Fireground Injuries,” Quincy, MA: National

Fire Protection Association, Fire Analysis and Research Division, Nov. 2003.

2. Fahy, R. and Leblanc, P., “On-Duty Deaths Firefighter Fatalities 2002,” National Fire

Protection Association Journal, Vol. 97, No. 4, pp 56-63, July/August 2003.

3. “Provisional Report for On-Duty Firefighter Fatalities in the United States Date Range

01/01/2003 to 12/31/2003 ,” Emittsburg, MD, US Fire Administation, updated Feb. 2004.

4. “Fire Fighter Deaths in Structural Collapses, 1979-1988.” Quincy, MA: National Fire

Protection Association, Fire Analysis and Research Division, Aug. 1989.

5. “Fire Ground Fatalities As A Result of Structural Collapse, 1983-1992.” Quincy, MA:

National Fire Protection Association, Fire Analysis and Research Division, Aug. 1993.

6. Brassell, L.D. and Evans, D.D., Trends in Firefighter Fatalities Due to Structural

Collapse, 1979-2002. NISTIR 7069. Gaithersburg, MD: National Institute of Standards

and Technology, Nov. 2003.

7. Standard on Personal Alert Safety Systems (PASS), 1998 Edition, Quincy, MA: National

Fire Protection Association, August 1998.

8. Fleming, R. P., “Theory of Automatic Sprinkler Performance.” Fire Protection

Handbook, Eighteenth Edition, Section 6/Chapter 8, Quincy, MA: National Fire

Protection Association, pp 6-113 – 6-123, 1997.

9. Taylor, B. N. and C. E. Kuyatt, Guidelines For Evaluating and Expressing the

Uncertainty of NIST Measurement Results. National Institute of Standards and

Technology (U.S.) NIST TN 1297; September, 20 p. 1994.

10. McGrattan, Kevin B.; Baum, Howard R.; Rehm, Ronald G.; Hamins, Anthony;

Forney, Glenn P.; “Fire Dynamics Simulator – Technical Reference Guide,”

National Institute of Standards and Technology, Gaithersburg, MD, NISTIR

6467, January 2000.
45

IX. Other Resources

United States Fire Administration Website - http://www.usfa.fema.gov/


46
47

Building and Fire Research Laboratory Website - http://www.bfrl/nist.gov
48

Appendix A.

Draft Performance Standard for Thermal Exposure Sensors for Personal Alert Safety Systems

(PASS).

Section A - DESIGN REQUIREMENTS

A.x Thermal Exposure Sensing Design Requirements for PASS.

A.x.1 PASS shall incorporate thermal sensing that shall detect high thermal environment near the

person on whom the PASS is deployed and cause the activation of the sequence that leads to the

sounding of the alarm signal when high thermal environment is detected for the specified time.

A.x.2 PASS shall sound the alarm signal specified in A.4.3 when the PASS does not sense the

thermal environment for 10 seconds, +2/-0 seconds.

A.x.3 PASS Thermal sensing shall function regardless of the angle of deployment of the PASS.

A.x.4 PASS shall be designed so that any failure of the thermal sensing function shall cause the

PASS to sound the alarm signal, specified in x.x.x, within 10 seconds, +2/-0 seconds, of such

failure. The PASS manufacturer shall submit a failure modes analysis to the certification

organization for verification of this requirement.

Section B - PERFORMANCE REQUIREMENTS

B.xx Thermal Exposure Sensor Test.

B.xx.1

PASS shall be tested for ability to sense the thermal environment as specified in Section C.xx,

Thermal Sensor Tests, and shall function as follows:

(a) PASS shall emit the operational signal, as specified in A.x.x.

(b) Signals shall be evaluated for proper functioning as specified in Section x.x

(c) The alarm signal shall sound and continue to sound, as specified in A.x.x.

(d) Signals shall meet the sound pressure levels as specified Section B.x

(e) Nothing shall fall off the PASS, and the PASS shall not fall from its mounted position.

(f) At least two separate and distinct manual actions shall be required to change the

mode selection device from alarm to sensing in order to silence the alarm as specified

in A.x.x.

(g) The data logging functions specified in A.x.x shall operate properly.

(h) The transmitter within the PASS shall remain functional after completion of this test

method.

(i) The data logging functions specified in A.x.x shall operate properly.
49

Section C - TEST METHODS

C.x Thermal Sensor Test.

C.x.1 Application. This test method shall apply to all PASS.

C.x.2 Samples.

C.x.2.1 Samples shall be complete PASS.

C.x.2.2 Samples shall be conditioned as specified in C.x.x.

C.x.3 Specimens.

C.x.3.1 Specimens for testing shall be complete PASS.

C.x.3.2 A minimum of three specimens shall be tested.

C.x.4 Procedure.

C.x.4.1 Each specimen shall be subjected to a series of three thermal sensing tests

identified as C.x.5, Test Procedure 1 for static environment, C.x.6, Test Procedure 2 for flow

environment, and C.x.7 Test Procedure 3 for radiation flux.

C.x.4.2 The same three specimens shall be used for all three test series. Each specimen tested

shall be complete with power supply.

C.x.4.3 The test chamber or cabinet shall be capable of maintaining the required conditions

specified in C.x.5, C.x.6, and C.x.7 throughout the envelope of air surrounding the specimen

being tested, and these conditions shall be continuously monitored.

C.x.4.4Following each test, the specimen shall be allowed to stabilize at ambient conditions prior

to proceeding to the next test.

C.x.5 Test Procedure 1 – Static Environment.

C.x.5.1 Specimens shall be removed following the specified conditioning, and testing shall begin

within 30 seconds of removal from conditioning.

C.x.5.2 Specimens shall be placed in an electric resistance oven that has been stabilized at 150°C

(120°F) +5/-0°F).

C.x.5.3 Specimens shall remain in oven until thermal sensor activates alarm.

C.x.5.4 PASS Device shall not alarm before 10 minutes, but shall alarm before 15 minutes of

exposure .

C.x.5.5 Failure of the alarm to activate within the specified time period shall constitute a failure.

C.x.5.6 This cycle shall be repeated twice for a total of three exposures.

C.x.5.7 Specimens shall be removed following the specified conditioning, and testing shall begin

within 30 seconds of removal from conditioning.

C.x.5.8 Specimens shall be placed in an electric resistance oven that has been stabilized at 300°C

(120°F) +5/-0°F).

C.x.5.9 Specimens shall remain in oven until thermal sensor activates alarm.

C.x.5.10 PASS Device shall not alarm before 5 seconds, but shall alarm before 15 seconds of

exposure.

C.x.5.11 Failure of the alarm to activate within the specified time period shall constitute a

failure.
50

C.x.5.12 This cycle shall be repeated twice for a total of three exposures.

C.x.6 Test Procedure 2 – Flow Environment.

C.x.6.1 Specimens shall be removed following the specified conditioning, and testing shall begin

within 30 seconds of removal from conditioning.

C.x.6.2 Specimens shall be placed in a heated flow loop that has been stabilized at 125°C

(250°F) +5/-0°F) and a flow velocity of 0.22 m/s.

C.x.6.3 Specimens shall remain in oven until thermal sensor activates alarm.

C.x.6.4 PASS Device shall not alarm before 15 minutes, but shall alarm before 20 minutes of

exposure .

C.x.6.5 Failure of the alarm to activate within the specified time period shall constitute a failure.

C.x.6.6 This cycle shall be repeated twice for a total of three exposures.

C.x.6.7 Specimens shall be removed following the specified conditioning, and testing shall begin

within 30 seconds of removal from conditioning.

C.x.6.8 Specimens shall be placed in a heated flow loop that has been stabilized at 250°C

(480°F) +5/-0°F) with a flow velocity of 1 m/s .

C.x.6.9Specimens shall remain in oven until thermal sensor activates alarm.

PASS Device shall not alarm before 5 seconds, but shall alarm before 15 seconds of exposure.

C.x.6.10 Failure of the alarm to activate within the specified time period shall constitute a

failure.

C.x.6.11This cycle shall be repeated twice for a total of three exposures.

C.x.7 Test Procedure 3 – Radiation Flux.

C.x.7.1 Specimens shall be removed following the specified conditioning, and testing shall begin

within 30 seconds of removal from conditioning.

C.x.7.2 Specimens shall be placed in a thermal flux field that has been stabilized at 2.5 w/m2.

C.x.7.3 Specimens shall remain in oven until thermal sensor activates alarm.

C.x.7.4 PASS Device shall not alarm before 10 minutes, but shall alarm before 15 minutes of

exposure .

C.x.7.5 Failure of the alarm to activate within the specified time period shall constitute a failure.

C.x.7.6 This cycle shall be repeated twice for a total of three exposures.

C.x.7.7 Specimens shall be removed following the specified conditioning, and testing shall begin

within 30 seconds of removal from conditioning.

C.x.7.8 Specimens shall be placed in a thermal flux field that has been stabilized at 30 w/m2.

C.x.7.9 Specimens shall remain in oven until thermal sensor activates alarm.

PASS Device shall not alarm before 5 seconds, but shall alarm before 15 seconds of exposure.

C.x.7.10 Failure of the alarm to activate within the specified time period shall constitute a

failure.

C.x.7.11 This cycle shall be repeated twice for a total of three exposures.

C.x.8.1 The functioning of the specimens shall be recorded and reported.

C.x.9 Interpretation.

C.x.9.1 Pass or fail performance shall be determined for each specimen.

C.x.9.2 One or more specimens failing this test shall constitute failing performance.