NBSIR 76-990

Report of Fire Tests on Eight

TGS Semiconductor Gas

Sensor Residential Fire/

Smoke Detectors

Richard G. Bright

Center for Fire Research

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

April 1976

Final Report

Sponsored in party by: ^ Bureau of Engineering Sciences

Consumer Products Safety Commission

Washington, D. C.

NBSIR 76-990

REPORT OF FIRE TESTS ON EIGHT

TGS SEMICONDUCTOR GAS

SENSOR RESIDENTIAL FIRE/

SMOKE DETECTORS

Richard G. Bright

Center for Fire Research

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

April 1976

Final Report

Sponsored in part by:

Bureau of Engineering Sciences

Consumer Products Safety Comnnission

Washington, D. C.

U.S. DEPARTMENT OF COMMERCE, Elliot L. Richardson, Secretary

James A. Baker, III, Under Secretary

Dr. Betsy Ancker-Johnson, Assistartt Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Err^est Ambler, Acting Director

CONTENTS

Page

LIST OF TABLES iv

Abstract 1

1. INTRODUCTION 1

2. DESCRIPTION OF TEST SERIES 3

2.1. TGS Detectors 3

2.2. Conventional Smoke Detectors 3

2.3. Base Sensitivity Tests 3

2.4. Full-scale Fire Tests 5

3. RESULTS 6

3.1. Base Sensitivity Tests 6

3.2. Full-Scale Fire Tests 6

4. DISCUSSION AND CONCLUSIONS 6

4.1. Base Sensitivity Tests 6

4.2. Full-Scale Fire Tests 9

4.3. Other 10

5. ACKNOWLEDGEMENTS 11

6. REFERENCES 11

iii
LIST OF TABLES

Page

Table 1. List of TGS Detectors 4

Table 2. Base Sensitivity Test Results 7

Table 3. Full-Scale Fire Test Results . 8

5

iv
REPORT OF FIRE TESTS ON EIGHT TGS

SEMICONDUCTOR GAS SENSOR RESIDENTIAL

FIRE/SMOKE DETECTORS

Richard G. Bright

Abstract

At the request of the Bureau of Engineering

Sciences Consumer Product Safety Commission,

twenty-four Taguchi gas sensor (TGS) detectors,

representing eight manufacturers were tested to

the requirements of Section 22 (base sensitivity

tests) and Section 24 (full-scale fire tests) of

Underwriters' Laboratories Standard No. 217,

"Standard for Single and Multiple Station Smoke

Detectors." Two conventional single-station smoke

detectors, one an ionization chamber type and the

other a photoelectric type, were included in the

test series for comparison. Only one of the TGS

detectors was able to meet the requirements of

Section 22, base sensitivity tests. None of the

TGS detectors were able to meet the requirements

of Section 24, full-scale fire tests. The two

conventional smoke detectors met the requirements

of Section 22 and 24.

Key words: Detectors; fire detectors; gas detectors;

smoke detectors; Taguchi gas sensors.

1. INTRODUCTION

Recently, there has, appeared on the U.S. market a new

type of fire detector, which utilizes as its basic sensing

mechanism, a semiconductor, solid-state device commonly

referred to as a Taguchi gas sensor (TGS) . A complete

1
description of the sensor and its method of operation is contained in the report, NBSIR 74-591 [I]"'".

These TGS detectors, while essentially combustible gas

detectors, are being marketed in increasing numbers as

either a fire detector or as a smoke detector, and sometimes

as both. There has been some concern with the use of these

as fire/smoke detectors due to their apparent limitation in

sensing or detecting freely-burning fires with adequate

oxygen supply. This concern is heightened by the fact that

conventional smoke detectors utilizing the ionization chamber

principle or the photoelectric principle do not exhibit this

same limitation and yet the TGS detector is being advertised

and sold as a satisfactory substitute for these conventional

smoke detectors. (See reference [2] for a technical description of conventional smoke detectors.)

In an attempt to explore the response characteristics

of commercially available TGS detectors more fully, arrangements were made with the Underwriters' Laboratories, Inc.

(UL) , to conduct a series of tests on several representative

TGS detectors. The test series was requested by the Bureau

of Engineering Sciences, Consumer Product Safety Commission.

The test series UL was asked to conduct are the same ones to

which conventional smoke detectors are subjected and must

pass before receiving UL approval. The results of the test,

series are reported herein.

Bracketed numbers refer' to references located at the end

of this paper.

2
2. DESCRIPTION OF TEST SERIES

2.1. TGS Detectors

Three samples each, of eight different manufacturers'

models, were obtained for the test series. Six of the eight

models are advertised as smoke detectors. Four of the models

have been tested and approved by the Factory Mutual System

as fire detectors and are so listed in their current Approval

Guide [3] . Table 1 presents a synopsis of this information.

For comparison purposes, two conventional smoke detectors

were included in the test series. One of these detectors

was an ionization-chamber-type smoke detector and the other

was a photoelectric-type smoke detector. Both of the conventional smoke detectors were a single-station smoke type,

i.e., designed for residential application.

All twenty-four of the TGS detectors, as well as the

two conventional smoke detectors, were subjected to the base

sensitivity tests using gray-colored smoke as described in

Section 22 of UL Standard No. 217 [4] . In this test sequence,

the detectors are placed, one-by-one, in a closed chamber.

The air in the chamber is circulated past the detector by a

fan. Smoke is introduced into the chamber from a smoldering

cotton lamp wick. The smoldering lamp wick produces a

linear increase in the smoke density in the chamber with

time. At some point, depending on the alarm threshold of the

detector, the smoke density is sufficient to produce an

alarm in the detector. The smoke density or opacity of the

smoke is measured by a photometer system. The output of the

2.2. Conventional Smoke Detectors

2.3. Base Sensitivity Tests

3
Table 1. List of TGS Detectors

FM Advertised as

Manufacturer Sample No. Approved Smoke Detector

A 1 No Yes

TV Z NO les

A 3 No Yes

B 4 No Yes

DD

cD JNO les

B 6 No Yes

C 7 No No

o

o No No

C 9 No No

D 10 Yes Yes

FND 1 11 Yes Yes

D 12 Yes Yes

E 13 Yes Yes14 Yes XT — _ Yes

V. E 15 Yes Yes

F 16 Yes No

r 1 / Yes No

F 18 Yes No

G 19 No Yes

G 20 MoiNlJ G 21 No Yes

H 22 Yes Yes

H 23 Yes Yes

H 24 Yes Yes

4
photometer is converted to smoke obscuration in percent-perfoot and, in addition, to optical density-per-foot.

Where individual sensitivity test trials varied by more

than + 1 microampere five trials were conducted with the

final sensitivity value being the average of the three mean

readings. If the individual variance was less than 1 microampere, three trials were taken.

If the TGS detector design was directional, base sensitivity tests were taken in the worst expected condition and

the position tested was recorded. One TGS detector model

had a consumer adjustable sensitivity control. This model

was tested at both its minimum and maximum sensitivity

settings.

2.4. Full-scale Fire Tests

All TGS detector samples, which were still operational

following the base sensitivity test, were then subjected to

the full-scale fire tests as described in Section 24 of UL

Standard No. 217 [4] . These full-scale fire tests consist of

four test fires, conducted in a large room, using four different combustible materials. Two trials are made with each

combustible material. The combustible materials are 8 oz.

(250 g) of shredded paper, a small wood crib, 200 cc of gasoline, and 2 oz (60 g) of polystyrene. Complete details of

the test room, the test materials and conditions of test are

fully described in Section 24 of UL Standard No. 217 [4] and

in the Bukowski-Bright report [5] and therefore, will not be

detailed here.

5
3. RESULTS

3.1. Base Sensitivity Tests

Table 2 presents the results of the base sensitivity

tests. Section 22 of UL Standard No. 217 requires that for

acceptance a detector must have a base sensitivity between

-1 -1 , 0.2%-ft (0.0009 optical density-ft /0.0073 optical

-1 -1 -1

density-m ) and 4.0%-ft (0.0177 optical density-ft /0.058

optical density-m ) . For those detectors having consumer

sensitivity adjustments, both maximum and minimum consumerset sensitivities would have to be within the 0.2 and 4.0

percent-per-foot ranges.

3.2. Full-scale Fire Tests

Table 3 presents the results of the full-scale fire

tests. The requirements for approval in these tests, according to Section 24 of UL Standard No. 217 [4] , are detection of the paper fires, gasoline fires, and polystyrene

fires in 120 seconds and detection of the wood crib fires

in 240 seconds.

4. DISCUSSION AND CONCLUSIONS

4.1. Base Sensitivity Tests

Of the 24 samples submitted for test, two were defective

upon delivery and could not be tested. Of the remaining 22

samples, only sample No. 9 met the requirements of the base

sensitivity test. Samples 4, 5 and 6, with the consumer

sensitivity adjustment, had maximum sensitivities within the

requirements but at minimum sensitivities these detectors

6
Table 2. Base Sensitivity Test Results

Sensitivity

at 30-35 fmp Orientation - Sample No. (%/ft) Smoke Flow Into

1 10.6 Right Side

2 24.8 Right Side

3 12.6 Right Side

4 1 .44 (Maximum) 6.89 (Minimum) Right Side

5 1 .87 (Maximum) 4.48 (Minimum) Right Side

6 1 .87 (Maximum) 5.14 (Minimum) Right Side

7 Defective on Receipt Right Side

8 20.48 Right Side

9 1.34 Right Side

10 23.62 Top

11 26.13 Tod

12 29.04 Top

13JL. ^ 6.10

(Defective After Sensitivity)

Top

14 4.06 Top

15 6.36 Top

16 Defective on Receipt Right Side

17 32.52 Right Side

18 11.27 Right Side

19 11.73 Right Side

20 13.09 Right Side

21 4.53 Right Side

22 5.77 Right Side

23 5.02 Right Side

24 5.95 Right Side

Photo 3.89 Top

Ion 1.87 Top

7
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did not meet the requirements. Both of the conventional

smoke detectors were within the acceptable range.

4.2. Full-Scale Fire Tests

None of the TGS detectors were able to detect all of

the test fires. Sample No. 9 detected all of the test fires

with exception of trial 2 of the gasoline fires. The requirements of Section 24 are, however, that each sample of a manufacturer's submittal must respond to at least one of each of

the test fires. The other sample of this manufacturer's

detectors, sample No. 8, was only able to detect the wood

fire and did not respond to the paper fire, the gasoline fire

or the polystrene fire.

It is of interest to compare the performance of the two

conventional smoke detectors to the TGS detectors . The ionization chamber smoke detector has a base sensitivity of

1.87%-ft~'^ (0.008 optical density-ft~ Vo . 027 optical densitym ) . This lies about half-way through the acceptable range.

Yet, its responses to the four full-scale fires were quick.

The photoelectric smoke detector had a base sensitivity

of 3.89%-ft~^ (0.017 optical density-ft~ Vo . 055 optical

density-m This detector, therefore, was fairly insensitive lying almost at the outer limit of the acceptable sensitivity range, but it was able to detect all the test fires

within the time limits, except the second paper trial.

9
4.3. Other

Sixteen of the TGS detectors carried the label of the

Factory Mutual (FM) indicating the detectors had been tested

and approved by FM and are so listed in the current edition

of Factory Mutual's Approval Guide [3]. Although FM lists

the TGS detectors as fire detectors, and not as smoke detectors, FM conducts tests on the TGS detectors using the guidelines set forth in FM Approval Standard Smoke Actuated

Detectors for Automatic Fire Alarm Signaling [6] in addition

to certain other tests.

The FM Approval Standard requires that the detectors

"respond to a source of visible smoke which produces a maximum light obscuration of 4%/ft." FM conducts this base sensitivity test in a test chamber similar to UL's. Even so, none

of the sixteen FM-approved TGS detectors met the FM base

sensitivity test requirements when tested in the UL test

chamber.

Detector samples 13, 14, 15, 22, 23 and 24 were only

slightly above the FM requirements. This may be attributable

to subtle differences between the UL and FM base sensitivity

test procedures. One known difference is in the wavelength

of the light source used in the photometric system. FM uses

a light source having a shorter wavelength (whiter) than

UL's (redder). For the same smoke concentration, a whiter

light will produce a lower apparent optical density than a

redder light. The result would be that a detector tested in

the FM chamber would appear to be more sensitive than the

same detector tested in the UL chamber. This variation in

optical density (smoke concentration) with wavelength of

light has been described by the British Fire Research Station

10
[7] . This explanation is not adequate, however, to explain

the base sensitivity test results for the other detector

samples

.

5 . ACKNOWLEDGEMENTS

The research described in this report was sponsored in

part by the Bureau of Engineering Sciences, Consumer Product

Safety Commission, Washington, D.C.

6. REFERENCES

[1] Bukowski, R. W. and Bright, R. G. , Some Problems Noted

in the Use of Taguchi Semiconductor Gas Sensors as

Residential Fire/Smoke Detectors, National Bureau of

Standards (U.S.), NBSIR 74-591 (Dec. 1974).

[2] Custer, R. L. P. and Bright, R. G. , Fire Detection: The

State-of-the-Art , National Bureau of Standards (U.S.),

NBS Technical Note 839 (June 1974).

[3] Approval Guide 1975, Factory Mutual System, 1151 BostonProvidence Turnpike, Norwood, Mass. 02062.

[4] Standard for Single and Multiple Station Smoke Detectors,

UL 217, Proposed First Edition, Underwriters' Laboratories, Inc., Chicago, 111. 60062 (March 7, 1975).

[5] Bukowski, R. W. and Bright, R. G., Results of Full-Scale

Fire Tests with Photoelectric Smoke Detectors, National

Bureau of Standards (U.S.), NBSIR 75-700 (June 1975).

11
[6] Approval Standard Smoke Actuated Detectors for Automatic

Fire Alarm Signaling, Class No. 3230-3250, Feb. 1973,

Factory Mutual System, 1151 Boston-Providence Turnpike,

Norwood, Mass. 02062.

[7] Fire Research 1971, Report of the Director, Fire Research Station, Borehamwood, Herts., England, pp. 62-

63, 1972.

USCOMM-NBS-DC

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NBS-1 14A (REV. 7 7 3)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUMLK ATION OR R1-:P0RT NO.

NBSIR 76-990

2. Gov't Acces.sion

No.

3. Rec ipicnl '.s Acccs.'iion No.

4, TITLr: AND SUBTITLE

Report of Fire Tests on Eight TGS Semiconductor

Gas Sensor Residential Fire/Smoke Detectors

5. Publication Date

April 1976

6. Performing Organization Code

7. AUTHOR(S)

Richard G. Bright

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

492 8677

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Bureau of Engineering Sciences

Consumer Products Safety Commission

Washington, D.C.

13. Type of Report & Period

Covered

Final Report

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or /ess factual sununary of most si^ificant information. If document includes a significant

bibliography or literature survey, mention it here.)

At the request of the Bureau of Engineering Sciences Consumer

Product Safety Commission, twenty-four Taguchi gas sensor (TGS)

detectors, representing eight manufacturers were tested to the

requirements of Section 22 (base sensitivity tests) and Section 24

(full-scale fire tests) of Underwriters' Laboratories Standard

No. 217, "Standard for Single and Multiple Station Smoke Detectors."

Two conventional single-station smoke detectors, one an ionization

chamber type and the other a photoelectric type, were included in

the test series for comparison. Only one of the TGS detectors was

able to meet the requirements of Section 22, base sensitivity tests.

None of the TGS detectors were able to meet the requirements of

Section 24, full-scale fire tests. The two conventional smoke

detectors met the requirements of Section 22 and 24.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of tfie first key word unless a proper name; separated by semicolons) Qetectors ; fire detectors; gas detectors; smoke

detectors; Taguchi gas sensors.

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(THIS REPORT)

UNCL ASSIFIED

21, NO. OF PAGES

16

20. SECURITY CLASS

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UNCLASSIFIED

22. Price

$3.50

18. AVAILABILITY Unlimited

d For Official Di stribution. Do Not Release to NTIS

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