NIST Technical Note 1763 

Smoke Component Yields from Benchscale Fire Tests: 4. Comparison with 

Room Fire Results 

Nathan D. Marsh 

Richard G. Gann 

 

NIST Technical Note 1763
 

Smoke Component Yields from Benchscale Fire Tests: 4. Comparison with 

Room Fire Results 

Nathan D. Marsh 

Richard G. Gann 

Fire Research Division 

Engineering Laboratory 

December 2013 

U.S. Department of Commerce 

Penny Pritzker, Secretary 

National Institute of Standards and Technology 

Patrick D. Gallagher, Under Secretary of Commerce for Standards and Technology and Director 
Certain commercial entities, equipment, or materials may be identified in this 

 document in order to describe an experimental procedure or concept adequately. 

Such identification is not intended to imply recommendation or endorsement by the 

National Institute of Standards and Technology, nor is it intended to imply that the 

entities, materials, or equipment are necessarily the best available for the purpose. 

National Institute of Standards and Technology Technical Note 1763 

Natl. Inst. Stand. Technol. Tech. Note 1763, 41 pages (December 2013) 

CODEN: NTNOEF
 
ABSTRACT 

A standard procedure is needed for obtaining smoke toxic potency data for use in fire hazard and 

risk analyses. Room fire testing of finished products is impractical, directing attention to the use 

of apparatus that can obtain the needed data quickly and at affordable cost. In this work we 

compare yields of toxic gases generated by four bench scale apparatus to previously conducted 

room-scale fires. The bench scale apparatus are the radiant apparatus in NFPA 269 and ASTM E 

1678, the smoke density chamber in ISO 5659-2, a controlled-atmosphere version of the cone 

calorimeter (ASTM E 1354),and the tube furnace in ISO/TS 19700. In the bench scale 

experiments, the test specimens were cut from finished products that were also burned in the 

room-scale tests: a sofa made of upholstered cushions on a steel frame, particleboard bookcases 

with a laminated finish, and household electric cable. The yields of CO2 CO, HCl, and HCN 

were determined. The yields of other toxicants (NO, NO2, formaldehyde, and acrolein) were 

below the detection limits, but volume fractions at the detection limits were shown to be of 

limited toxicological importance relative to the detected toxicants. The bench scale and room 

scale yields are compared, and the bench scale apparatus are assessed for the degree to which 

they accurately predict room scale yields. The results of this study provide a better basis for 

obtaining toxic potency input data for fire modeling than currently exists. 

Keywords: fire, fire research, smoke, room fire tests, fire toxicity, smoke toxicity 

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TABLE OF CONTENTS
 

LIST OF TABLES ......................................................................................................................................................... VI
 

EXECUTIVE SUMMARY ............................................................................................................................................ VII
 

I. INTRODUCTION......................................................................................................................................... 1
 

A. CONTEXT OF THE RESEARCH ........................................................................................................................................1
 

B. OBTAINING INPUT DATA.............................................................................................................................................2
 

II. TESTING IN THIS PROJECT.......................................................................................................................... 5
 

A. APPROACH..........................................................................................................................................................5
 

B. ROOM‐SCALE TESTS..............................................................................................................................................5
 

B. BENCH‐SCALE TESTS .............................................................................................................................................6
 

III. COMPILED DATA FROM ROOM‐ AND BENCH‐SCALE TESTS......................................................................... 9
 

IV. ANALYSIS .................................................................................................................................................17
 

A. FIRE STAGES......................................................................................................................................................17
 

B. APPLICABILITY....................................................................................................................................................17
 

C. APPARATUS INDEPENDENCE .................................................................................................................................18
 

D. OPERATIONAL EFFICIENCY ....................................................................................................................................19
 

E. DATA GENERATED...............................................................................................................................................19
 

F. ACCURACY OF THE PHYSICAL FIRE MODELS ...............................................................................................................19
 

1. CO2 ............................................................................................................................................................20
 

2. CO .............................................................................................................................................................22
 

3. HCl ............................................................................................................................................................24
 

4. HCN...........................................................................................................................................................26
 

5. HBr and HF................................................................................................................................................27
 

6. NO2, Acrolein and Formaldehyde..............................................................................................................27
 

V. RECOMMENDATIONS ON THE USE OF BENCH‐SCALE APPARATUS FOR OBTAINING TOXIC GAS YIELDS FOR
 

USE IN FIRE HAZARD AND RISK ANALYSES .........................................................................................................29
 

A. EFFECT ON HEAT RELEASE....................................................................................................................................29
 

B. EFFECT ON TENABILITY CALCULATIONS ...................................................................................................................30
 

C. RECOMMENDATIONS ..........................................................................................................................................32
 

REFERENCES............................................................................................................................................................35
 

v 
                    

              

              

              

                    

                    

                    

                      

                       

                       

                       

                         

LIST OF TABLES 

TABLE 1. CALCULATED NOTIONAL YIELDS OF TOXIC PRODUCTS FROM THE TEST SPECIMENS. ............................................................9
 

TABLE 2. YIELDS OF COMBUSTION PRODUCTS FROM BOOKCASE SPECIMENS ...............................................................................10
 

TABLE 3. YIELDS OF COMBUSTION PRODUCTS FROM SOFA SPECIMENS.......................................................................................11
 

TABLE 4. YIELDS OF COMBUSTION PRODUCTS FROM CABLE SPECIMENS .....................................................................................12
 

TABLE 5. FRACTIONS OF NOTIONAL YIELDS OF COMBUSTION PRODUCTS FROM BOOKCASE SPECIMENS ............................................13
 

TABLE 6. FRACTIONS OF NOTIONAL YIELDS OF COMBUSTION PRODUCTS FROM SOFA SPECIMENS....................................................14
 

TABLE 7. FRACTIONS OF NOTIONAL YIELDS OF COMBUSTION PRODUCTS FROM CABLE SPECIMENS ..................................................15
 

TABLE 8. CO2 YIELDS FROM BENCH‐SCALE TESTS RELATIVE TO YIELDS FROM ROOM TESTS. ...........................................................22
 

TABLE 9. CO YIELDS FROM BENCH‐SCALE TESTS RELATIVE TO YIELDS FROM ROOM TESTS. .............................................................24
 

TABLE 10. HCL YIELDS FROM BENCH‐SCALE TESTS RELATIVE TO YIELDS FROM ROOM TESTS. ..........................................................26
 

TABLE 11. HCN YIELDS FROM BENCH‐SCALE TESTS RELATIVE TO YIELDS FROM ROOM TESTS. .........................................................28
 

TABLE 12. FRACTIONS OF NOTIONAL YIELDS OF CO2 IN THE EFFLUENT FROM FIRE TESTS................................................................29
 

vi 
EXECUTIVE SUMMARY 

Estimation of the times that building occupants will have to escape, find a place of refuge, or 

survive in place in the event of a fire is a principal component in the fire hazard or risk 

assessment of a facility. An accurate assessment enables public officials and facility owners to 

provide a selected or mandated degree of fire safety with confidence. Without this confidence, 

regulators and/or designers tend to apply large safety factors to lengthen the tenable time. This 

can increase the cost in the form of additional fire protection measures and can eliminate the 

consideration of otherwise desirable facility designs and construction products. Error in the 

other direction is also risky, in that if the time estimates are incorrectly long, the consequences of 

a fire could be unexpectedly high. 

Such fire safety assessments now rely on some form of computation that takes into account 

multiple, diverse factors, including the facility design, the capabilities of the occupants, the 

potential growth rate of a design fire, the spread rates of the heat and smoke, and the impact of 

the fire effluent (toxic gases, aerosols, and heat) on people who are in or moving through the fire 

vicinity. The toolkit for these assessments includes computer models of the movement and 

distribution of fire effluent throughout a facility, laboratory devices which are routinely used to 

generate information on the rate of heat release as a commercial product burns, and a number of 

standards from ISO TC92 SC3 that provide support for the generation and use of fire effluent 

information in fire hazard and risk analyses. Of particular importance is ISO 13571, which 

provides consensus equations for estimating the human incapacitating exposures to the narcotic 

gases, irritant gases, heat, and smoke generated in fires. 

More problematic are the sources of data for the production of these harmful products of 

combustion. Different materials can generate fire effluent with a wide range of toxic potencies. 

Most furnishing and interior finish products are composed of multiple materials assembled in a 

variety of geometries, and there is as of yet no methodology for predicting the evolved products 

from these complex assemblies. 

An analysis of the U.S. fire fatality data showed that postflashover fires comprise the leading 

scenario for life loss from smoke inhalation. Thus, it is most important to obtain data regarding 

the generation of harmful species under postflashover (or otherwise underventilated) combustion 

conditions. Data for preflashover (well-ventilated) flaming conditions have value for 

ascertaining the importance of prolonged exposure to "ordinary" fire effluent and to short 

exposures to effluent of high potency. 

The universal metric for the generation of a toxic species from a burning specimen is the yield of 

that species, defined as the mass of the species generated divided by the consumed mass of the 

specimen. These yields are input to the calculations used to estimate fire hazard. 

A base set of the most prevalent harmful species is given in ISO 13571. To obtain an indicator 

of whether the base list of toxic species needs to be enhanced, living organisms should also be 

exposed to the fire effluent. However, it is recognized that animal testing is not always possible. 

In these cases, it is important to identify, from elemental analysis of the fuel and its degradation 

chemistry, a reasonable list of the combustion products that might be harmful to people. 

Typically, the overall effluent from a harmful fire is determined by the large combustibles, such 

as a bed or a row of auditorium seats. The ideal fire test specimen for obtaining the yields of 

effluent components is the complete combustible item, with the test being conducted in an 

vii 
enclosure of appropriate size. Unfortunately, reliance on real-scale testing of commercial 

products is impractical, both for its expense per test and for the vast number of commercial 

products used in buildings. Such testing is practical for forensic investigations in which there is 

knowledge of the specific items that combusted. 

A more feasible approach for obtaining toxic gas yields for facility design involves the use of a 

physical fire model – a small-scale combustor that captures the essence of the combustible and of 

the burning environment of interest. The test specimen is an appropriate cutting from the full 

combustible. To have confidence in the accuracy of the effluent yields from this physical fire 

model, it must be demonstrated: 

	 How to obtain, from the full combustible, a representative cutting that can be 

accommodated and burned in the physical fire model; 

	 That the combustion conditions in the combustor (with the test specimen in place) are 

related to the combustion conditions in the fire of interest; 

	 How well, for a diverse set of combustible items, the yields from the small-scale 

combustor relate to the yields from real-scale burning of the full combustible items; and 

	 How sensitive the effluent yields are to the combustor conditions and to the manner in 

which the test specimen was obtained from the actual combustible item. 

There have been numerous bench-scale devices that were intended for measuring the 

components of the combustion effluent, and at least three of these are under current scrutiny in 

the standards arena. Thus, before too long there may well be diverse (and perhaps conflicting) 

data on fire effluent component yields available for any given product. This situation does not 

support either assured fire safety or marketplace stability. 

The National Institute of Standards and Technology (NIST) has completed a project to establish 

a technically sound protocol for assessing the accuracy of bench-scale device(s) for use in 

generating fire effluent yield data for fire hazard and risk evaluation. A related intent was to 

identify the most appropriate bench-scale device(s), in their current stage(s) of development, for 

obtaining accurate toxic gas yields. 

In this protocol, the yields of harmful effluent components were determined for the real-scale 

burning of complete finished products during three fire stages: preflashover conditions, 

postflashover conditions, and underventilated burning in a closed room. These fuels were 

selected for diversity of physical form, combustion behavior, and the nature and yields of 

toxicants produced. They included “sofas” made of up to 14 upholstered cushions supported by 

a steel frame, particleboard bookcases with a laminated finish, and household wiring cable. 

In each of these tests, the "preflashover" data were for an approximately two-minute period after 

flaming was established, but before the flames accelerated in intensity toward flashover. The 

"postflashover" data were for a period of similar length after flames filled the test room. Two of 

the sofa tests were performed with the test room door sealed, a replication of ventilation limited 

fire that did not proceed to room flashover. 

Subsequently, NIST conducted bench-scale experiments with specimens cut from these 

combustibles and tested in four standard apparatus: (A) the radiant apparatus in NFPA 269 and 

NFPA E 1678, (B) the smoke density chamber in ISO 5659-2, (C) the tube furnace in ISO/TS 

19700, and (D) a controlled-atmosphere version of the cone calorimeter (ASTM E 1354). 

viii 
Each apparatus was operated according to the procedure in its Standard. In addition, the 

operating conditions in each apparatus were varied to determine the sensitivity of the test results 

to the test conditions and whether improved agreement with the room test results was possible. 

The variation included: cutting the test specimen into small pieces, varying the initial oxygen 

volume fraction, varying the added heat flux. For the tube furnace, some of the tests included 

varying the mass combusted and the air flow, while preserving the same fuel/air equivalence 

ratio. The standard for Apparatus C includes protocols for both well ventilated and 

underventilated combustion. The standards for the other three apparatus more closely replicate 

well ventilated burning. Varying the initial oxygen level was intend to examine the utility of the 

apparatus for burning in a vitiated environment. 

The concentrations of CO2, CO, and O2 were monitored using species-specific analyzers. 

Fourier transform infrared (FTIR) spectroscopy was used to monitor CO2, CO, HCN, HCl, NO, 

NO2, H2CO (formaldehyde), and C3H4O (CH2=CH-CH=O, acrolein). For all the gases except 

CO2 and CO, many or all of the measurements were below or close to the limits of detection. 

The upper limits to the gas yields were calculated using the detection limits. 

The equations in ISO 13571 were used to estimate the relative contributions of these gases to the 

tenability of the fire environment. The results for each of the test series are presented in 

referenced individual reports. Not surprisingly, the contribution of some of these gases to 

compromised tenability was of second order. This unimportance of secondary toxicants is 

consistent with the results of the animal experiments used to establish the N-gas hypothesis that 

attributes fire effluent lethality to a small number of gases. 

The test specimens in the apparatus A, B, and D were similar. The specimens of the same layout 

as in the finished product and were exposed to similar levels of thermal irradiation from above. 

The air flow to the burning zone was determined by natural convection. The tube dimensions in 

apparatus C necessitated using a long, narrow test specimen, and the specimen was heated on all 

sides. A preselected stream of air flowed to and over the specimen. 

It was necessary to develop criteria to characterize the degree of agreement between the gas 

yields from the bench-scale apparatus and the room tests. In practice, the needed accuracy is 

appropriately defined in terms of the acceptable uncertainty in the calculated times at which 

survival in a burning building is compromised. For the current study, it was decided that the 

calculation of the two markers of toxic potency, the fractional effective dose (FED) due to 

inhalation of narcotic gases and the fractional effective concentration (FEC) due to exposure to 

sensory irritants, each be sufficiently accurate to identify significant deviations from "ordinary" 

toxic hazard. Given the current state of the art in fire modeling and the limits of precision of the 

IC50 data, it was deemed reasonable that the accuracy be within a factor of two. 

The accuracies of the yields of the toxic gases are not equally important. Due to the prevalence 

of fire deaths due to smoke being from postflashover fires, a greater importance was attached to 

the postflashover gas yields. The yield of CO2 affects the carbon balance, and thus the 

relationship between the gas yields and the heat release. This, in turn, affects the calculated 

room temperatures and the burning rates of combustibles. It also exponentially increases a 

person's breathing rate and thus the volume of inhaled smoke. CO is an important toxicant in 

virtually all fires. When nitrogen is present in the fuel, it can also be a significant contributor to 

the FED. All three fuels in this study were nitrogen-containing, but HCN was only a contributor 

to the FED from the sofa materials. The cable was the only fuel that contained a high mass 

ix 
fraction of Cl, and HCl dominated the FEC. For the other two fuels, all the irritant 

concentrations were low, and tenability was dominated by the narcotic gases. 

The findings regarding the comparison between the gas yields from the room-scale tests and the 

bench-scale apparatus were as follows. 

	 CO2: The yields from apparatus A, B, and D were within experimental uncertainty of the 

postflashover room test yield and within a factor of 2 of the preflashover yield. 

The underventilated yield from apparatus C was low compared to the postflashover room 

value, and the well ventilated value was in agreement with the preflashover room value. 

The CO2 yields from all four apparatus agreed with the sofa material yield from the 

closed room tests to within a factor of 2. 

	 CO: None of the apparatus generated CO volume fractions comparable to the 0.2 value 

compiled from multiple series of postflashover room tests. This is because the 

postflashover CO yields result from room conditions that are not readily replicated in a 

simple bench-scale device. The yield value of 0.2 should be used in hazard calculations. 

The yields from Apparatus A and D agreed with the preflashover room yield within a 

factor of 2. Decreasing the oxygen volume fraction to 0.16 in Apparatus D appears to 

have improved the agreement. 

A decrease in the oxygen volume fraction to 0.18 in Apparatus D led to agreement with 

the closed room yield. 

	 HCl: For the cable, the yields from Apparatus A and D were within experimental 

uncertainty of the postflashover room yield. Decreasing the oxygen volume fraction in 

Apparatus D degraded the agreement, but it was still well within a factor of 2. The yields 

from Apparatus B and C were within a factor of 2 of the room test yield. 

The yields from all four apparatus were very high compared to the preflashover room test 

yield, which was a very low value. 

The upper limits of the HCl yields from the bench-scale tests of the sofa materials were 

too high for quantitative comparison with the very low yield from the closed room tests. 

	 HCN: The underventilated yield from Apparatus C tests of the sofa materials was within 

a factor of 2 of the postflashover room yield. The value from Apparatus D at an oxygen 

volume fraction of 0.21 was very low, but at a volume fraction of 0.16, the agreement 

was within experimental error. The values from the other apparatus were very low. 

The values for the sofa materials from Apparatus A, C, and D agreed with the 

preflashover room value within experimental uncertainty. 

The yields from the bench-scale tests of the sofa materials were within a factor of 2 of the 

closed room values for Apparatus A and D. The yield from Apparatus C operated at 

underventilated conditions was very high. 

The CO2 yields for underventilated burning of all three types of test specimens burned in the tube 

furnace were notably very low. We were unable to account for approximately two-thirds of the 

carbon. Qualitatively, there was no evidence in the FTIR spectra of large concentrations of 

gasified organic material, nor was there unusual residue in the downstream portion of the tube or 

x 
in the collection chamber. The mass losses from the test specimens were close to the mass losses 

in the other three bench-scale apparatus. This an issue that merits further research. 

It should not be surprising that physical fire models, being imperfect approximations of some 

stage of real-scale burning, did not precisely predict the yields of multiple toxic gases from a set 

of diverse, non-homogeneous products that burned quite differently from each other. It should 

also not be surprising that under certain test conditions, the yields from both the room tests and 

the physical fire models showed large uncertainties. Nonetheless, one of the purposes of this 

project was to identify the more promising physical fire models to use for obtaining input data 

for fire hazard and risk analysis. The data indicate the following choices: 

Underventilated fires: 

	 The cone calorimeter operated at 50 kW/m2

 and a reduced oxygen volume fraction in the 

range of 0.16 to 0.18. 

Well ventilated fires: 

	 The cone calorimeter operated at 50 kW/m2

 and an oxygen volume fraction of 0.21. 

None of the apparatus predict the HCl yield within a factor of two. 

There are some recommendations regarding modifications to the standard operating conditions 

for these physical fire models. 

	 In all cases, the CO yields from the physical fire model should be adjusted to 0.2. 

	 In the radiant furnace, the shutter isolating the combustion chamber from the collection 

chamber should be closed immediately following the cessation of flaming. 

	 For the products examined, there was no sizable effect of cutting the specimens into 

small pieces. However, it is likely that the effect would be significant if some or all of 

the combustible mass were intentionally being protected by a fire barrier. 

	 The extensive ongoing research using various designs of the cone calorimeter with 

variable oxygen volume fraction and total inflow should include measurement of toxic 

species. This would further refine the operating conditions that provide the broadest 

agreement with the gas yields from room fire tests. 

Further investigation of the tube furnace is warranted. It is important to understand why the CO2 

yields for the underventilated condition are low and why the yields from the well ventilated 

condition are in agreement with the postflashover fire stages of the room fires for all three 

combustibles. It would also be helpful to understand the observed changes in some yields when 

the same equivalence ratio was achieved with different combinations of mass and air flow. 

The results of this study provide a better basis for obtaining toxic potency input data for fire 

modeling than currently exists. A more robust basis for future engineering assessments of fire 

safety designs would result from the performance of 

	 Room-scale tests with more combustibles and room placements. 

	 Parametric runs of a zone or field fire model in order to define better the effect of input 

data accuracy and variability on the times to threats to building occupant life safety. 

xi 
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xii 
 

 

I. INTRODUCTION 

A. CONTEXT OF THE RESEARCH 

Estimation of the times that building occupants will have to escape, find a place of refuge, or 

survive in place in the event of a fire is a principal component in the fire hazard or risk 

assessment of a facility. An accurate assessment enables public officials and facility owners to 

provide a selected or mandated degree of fire safety with confidence. Without this confidence, 

regulators and/or designers tend to apply large safety factors to lengthen the tenable time. This 

can increase the cost in the form of additional fire protection measures and can eliminate the 

consideration of otherwise desirable facility designs and construction products. Error in the 

other direction is also risky, in that if the time estimates are incorrectly long, the consequences of 

a fire could be unexpectedly high. 

Such fire safety assessments now rely on some form of computation that takes into account 

multiple, diverse factors, including the facility design, the capabilities of the occupants, the 

potential growth rate of a design fire, the spread rates of the heat and smoke, and the impact of 

the fire effluent (toxic gases, aerosols, and heat) on people who are in or moving through the fire 

vicinity.1

 The toolkit for these assessments, while still evolving, has achieved some degree of 

maturity and quality. The kit includes such tools as: 

 Computer models of the movement and distribution of fire effluent throughout a facility. 

o	 Zone models, such as CFAST2, have been in use for over two decades. This 

model takes little computational time, a benefit achieved by simplifying the air 

space in each room into two zones. A number of laboratory programs, validation 

studies,3

 and reconstructions of actual fires have given credence to the 

predictions.4 

o	 Computational fluid dynamics (CFD) models, such as the Fire Dynamics 

Simulator (FDS)5

, have seen increased use over the past decade. FDS is more 

computationally intense than CFAST in order to provide three-dimensional 

temperature and species concentration profiles. There has been extensive 

verification and validation of FDS predictions.5 

These models calculate the temperatures and combustion product concentrations as the 

fire develops. These profiles can be used for estimating when a person would die or be 

incapacitated, i.e., is no longer able to effect his/her own escape. 

 Devices such as the cone calorimeter6

 and larger scale apparatus7, which are routinely 

used to generate information on the rate of heat release as a commercial product burns. 

 A number of standards from ISO TC92 SC3 that provide support for the generation and 

use of fire effluent information in fire hazard and risk analyses.8 Of particular 

importance is ISO 13571, which provides consensus equations for estimating the human 

incapacitating exposures to the narcotic gases, irritant gases, heat, and smoke generated 

in fires.9 

More problematic are the sources of data for the production of the harmful products of 

combustion. Different materials can generate fire effluent with a wide range of toxic potencies. 

Most furnishing and interior finish products are composed of multiple materials assembled in a 

variety of geometries, and there is as of yet no methodology for predicting the evolved products 

1 
 

from these complex assemblies. Furthermore, the generation of carbon monoxide (CO), the most 

common toxicant, can vary by orders of magnitudes, depending on the fire conditions.10 

An analysis of the U.S. fire fatality data11 showed that postflashover fires comprise the leading 

scenarios for life loss from smoke inhalation. Thus, it is most important to obtain data regarding 

the generation of harmful species under postflashover (or otherwise underventilated) combustion 

conditions. Data for preflashover (well-ventilated) flaming conditions have value for 

ascertaining the importance of prolonged exposure to "ordinary" fire effluent and to short 

exposures to effluent of high potency. 

B. OBTAINING INPUT DATA 

The universal metric for the generation of a toxic species from a burning specimen is the yield of 

that species, defined as the mass of the species generated divided by the consumed mass of the 

specimen.12 If both the mass of the test specimen and the mass of the evolved species are 

measured continuously during a test, then it is possible to obtain the yields of the evolved species 

as the burning process, and any chemical change within the specimen, proceeds. If continuous 

measurements are not possible, there is still value in obtaining a yield for each species integrated 

over the burning history of the test specimen. 

The concentrations of the gases (resulting from the yields and the prevalent dilution air) are 

combined using the equations in ISO 13571 for a base set of the most prevalent toxic species. 

Additional species may be needed to account for the toxic potency of the fire-generated 

environment. 

To obtain an indicator of whether the base list of toxic species needs to be enhanced, living 

organisms should also be exposed to the fire effluent. The effluent exposure that generates an 

effect on the organisms is compared to the effect of exposure to mixtures of the principal toxic 

gases. Disagreement between the effluent exposure and the mixed gas exposure is an indicator 

of effluent components not included in the mixed gas data or the existence of synergisms or 

antagonisms among the effluent components. This procedure has been standardized, based on 

data developed using laboratory rats.13,14 However, it is recognized that animal testing is not 

always possible. In these cases, it is important to identify, from the elemental analysis of the fuel 

and its degradation chemistry, a reasonable list of the combustion products that might be harmful 

to people. 

Typically, the overall effluent from a harmful fire is determined by the large combustibles, such 

as a bed or a row of auditorium seats. The ideal fire test specimen for obtaining the yields of 

effluent components is the complete combustible item, with the test being conducted in an 

enclosure of appropriate size. Unfortunately, reliance on real-scale testing of commercial 

products is impractical, both for its expense per test and for the vast number of commercial 

products used in buildings. Such testing is practical for forensic investigations in which there is 

knowledge of the specific items that combusted. 

A more feasible approach for obtaining toxic gas yields for facility design involves the use of a 

physical fire model – a small-scale combustor that captures the essence of the combustible and of 

the burning environment of interest. The test specimen is an appropriate cutting from the full 

combustible. To have confidence in the accuracy of the effluent yields from this physical fire 

model, it must be demonstrated: 

2 
 

	 How to obtain, from the full combustible, a representative cutting that can be 

accommodated and burned in the physical fire model; 

	 That the combustion conditions in the combustor (with the test specimen in place) are 

related to the combustion conditions in the fire of interest, generally preflashover flaming 

(well ventilated or underventilated), postflashover flaming, pyrolysis, or smoldering; 

	 How well, for a diverse set of combustible items, the yields from the small-scale 

combustor relate to the yields from real-scale burning of the full combustible items; and 

	 How sensitive the effluent yields are to the combustor conditions and to the manner in 

which the test specimen was obtained from the actual combustible item. 

Historically, there have been numerous bench-scale devices that were intended for measuring the 

components of the combustion effluent.15,16 The combustion conditions and test specimen 

configuration in the devices vary widely, and some devices have flexibility in setting those 

conditions. Currently, ISO TC92 SC3 (Fire Threat to People and the Environment) is proceeding 

toward standardization of one of these devices, a tube furnace (ISO/TS 1970017) and is 

considering standardization of another, the cone calorimeter (ISO 5660-16) with a controlled 

combustion environment. There are concurrent efforts in Europe and ISO to upgrade the 

chemical analytical capability for a closed box test (ISO 5659-218). Thus, before too long there 

may well be diverse (and perhaps conflicting) data on fire effluent component yields available 

for any given product. This situation does not support either assured fire safety or marketplace 

stability. 

Only one device, used in both NFPA 26913 and ASTM E167814, has been validated with animal 

exposure and gas measurement data against real-scale fire test data for the same materials, and 

then only for postflashover yields of the principal toxicants.19 The three, relatively homogeneous 

materials were Douglas fir, a rigid polyurethane foam, and an unplasticized PVC. The 

toxicology of the combustion products varied significantly among the three materials. 

Laboratory rats were exposed to the combustion effluent for 30 min and then observed for 

14 days. The times of any animal deaths were recorded. The yields of the principal toxicants 

were also determined. 

The validation was conducted according to five hypotheses: 

1.	 The equal LC50 hypothesis: LC50 valuesi

, as measured in the bench-scale test and in the 

real scale, agree to within the acceptable uncertainty. 

2.	 The primary toxic gas hypothesis: The bench-scale test shows the same primary toxic 

gases as the real-scale test. 

3.	 The equal yields hypothesis: The yields of the measured toxic gases are the same, to 

within the acceptable uncertainty, in the bench-scale and in the real-scale tests. 

4.	 The N-gas hypothesis: The real-scale and the bench-scale results agree, to with the 

acceptable uncertainty, with predictions based on measured gas concentration and 

computations made according to the N-gas Model.ii 

i

 The LC50 is the concentration of a species or of smoke that leads to the death of half (50 %) of the test animals 

within a specified time interval. An analogous metric is the IC50, where the observed response is incapacitation. 

3 
 

5.	 The type-of-death hypothesis: The type of death (within- or post-exposure) is similar for 

the bench-scale and for the real-scale tests. 

The agreement between the bench-scale results and the real-scale results was deemed to be 

within a factor of three, based on the hypothesis with the worst agreement. The LC50 values 

agreed within approximately ± 50 %. 

At some point, there will be sufficient data to imbue confidence that testing of further 

combustibles in a particular physical fire model will generate yields of effluent components with 

a consistent degree of accuracy. 

ii When polymeric materials are thermally decomposed and burned, there are hundreds of species in the effluent. 

The N-gas model postulates that the toxic potency of the effluent can be substantially explained using a small 

number, N, of these species. Typically, N is fewer than 10. 

4 
II. TESTING IN THIS PROJECT 

A. APPROACH 

The National Institute of Standards and Technology (NIST) has completed a project to establish 

a technically sound protocol for assessing the accuracy of bench-scale device(s) for use in 

generating fire effluent yield data for fire hazard and risk evaluation. In this protocol, the yields 

of harmful effluent components were determined for the real-scale burning of complete finished 

products during both preflashover and postflashover conditions. Specimens cut from these 

products were then burned in various types of bench-scale combustors using their standard test 

protocols. These test protocols were then varied within the range of the combustion conditions 

related to these fire stages to determine the sensitivity of the test results to the test conditions and 

to provide a basis for improving the degree of agreement with the yields from the room-scale 

tests. 

This project did not explicitly include the nonflaming fire stages. While there is evidence that 

people can experience lethal exposures to the smoke from smoldering fires, it was apparent that 

none of the bench-scale devices were intended for repeatable creation of this form of 

combustion. The nature and yields of pyrolysis products are sensitive to the geometry of the 

location of the heating source, its interaction with the test specimen, and the volume fraction of 

oxygen in the air. Therefore, study of these fire stages was reserved for future consideration. 

B. ROOM-SCALE TESTS 

Initially, NIST conducted room-scale fire tests of three combustible items.20 These fuels were 

selected for diversity of physical form, combustion behavior, and the nature and yields of 

toxicants produced. 

	 “Sofas” made of up to 14 upholstered cushions supported by a steel frame. The cushions 

consisted of a zippered cotton-polyester fabric over a block of a flexible polyurethane 

(FPU) foam. The fire retardant in the cushion padding contains chlorine atoms. Thus, 

this fuel would be a source of CO2, CO, HCN, HCl, and partially combusted organics. 

The ignition source was the California TB133 propane ignition burner21 faced downward, 

centered over the center of the row of seat cushions. The sofa was centered along the rear 

wall of the burn room facing the doorway. Two of the sofa tests were conducted in a 

closed room to examine the effect of vitiation on fire effluent generation. In these, an 

electric “match” was used to initiate the fires. 

	 Particleboard (ground wood with a urea formaldehyde binder) bookcases with a 

laminated polyvinylchloride (PVC) finish. This fuel would be a source of CO2, CO, 

partially combusted organics, HCN, and HCl. To sustain burning, two bookcases were 

placed in a “V” formation, with the TB133 burner facing upward under the lower shelves. 

5 
	 Household wiring cable, consisting of two 14 gauge copper conductors insulated with 

nylon and polyvinyl chloride (PVC), an uninsulated ground conductor, two paper filler 

strips, and an outer jacket of plasticized PVC. This fuel would be a source of CO2, CO, 

HCl, and partially combusted organics. Two cable racks containing 3 trays each 

supported approximately 30 kg of cable in each of the bottom two trays and 

approximately 17 kg in each of the middle and top trays. The cable trays were placed 

parallel to the rear of the burn room. Twin propane ignition burners were centered under 

the bottom tray of each rack. 

Data on these fuels are included as Appendix A. 

In each of these tests, the "preflashover" data were for an approximately two-minute period after 

flaming was established, but before the flames accelerated in intensity toward flashover. The 

"postflashover" data were for a period of similar length after flames filled the test room. 

Two sofa tests were performed with the test room door sealed. The effluent was sampled from 

the upper layer of the burn room. In both tests, the oxygen volume fraction declined to 

approximately 0.11 near 300 s into the test. At 500s, the oxygen volume fraction had stabilized 

at 0.12, indicating that any continuing combustion was minimal and that the gas mixing in the 

room was nominally complete. Thus, the calculated gas yields at 500 s were used for 

comparison with the bench-scale data described next. 

B. BENCH-SCALE TESTS 

Subsequently, NIST conducted bench-scale experiments with specimens cut from these 

combustibles and tested in four standard apparatus. 

	 The radiant apparatus in NFPA 26913 and NFPA E 167814, with the NIST testing 

described in Reference 22. 

	 The smoke density chamber in ISO 5659-218, with the NIST testing described in 

Reference 23. 

	 A controlled-atmosphere version of the cone calorimeter (ASTM E 13546), with the 

NIST testing described in Reference 24. 

	 The tube furnace in ISO/TS 1970017, with the NIST testing described in Reference 25. 

The test specimens for the bookcase and cable tests were pieces of the actual combustible – a 

slab of the laminated particle board and lengths of the cable, respectively. The sofa material 

specimens in the first three apparatus were a layer of fabric over a slab of the foam. A similar 

array was cut to shape to fit in the tube furnace. 

Each apparatus was operated according to the procedure in its Standard. In addition, the 

operating conditions in each apparatus were varied to determine whether improved agreement 

with the room test results was possible. One of the variations, common to all the bench-scale 

tests but the cone calorimeter, was to cut the test specimen into small pieces. This increased the 

surface area for burning. For the cable, this also increased the direct exposure of the nylon 

jacketing to air and the external flux field. Diced specimens were not tested in the cone 

calorimeter because data from the other three apparatus, all of which also involved radiative 

exposure of the test specimens, showed little to no effect of this variation. 

6 
The other variations were: 

	 Radiant apparatus. The initial oxygen volume fraction was reduced to 0.17. 

	 Smoke density chamber. This was operated at three of the prescribed conditions: 

50 kW/m2

 irradiance with and without a pilot flame, and 25 kW/m2 irradiance with a pilot 

flame. 

	 Cone calorimeter. All tests were performed with a housing encasing the load cell and 

radiant source and sealed to the collection hood. The oxygen volume percent in the 

incoming air was reduced to as low as 14 %. The specimen irradiance was either 

50 kW/m2 or 25 kW/m2 . In some tests, the air flow past the specimen was reduced by 

half to 12.5 L/s. 

	 Tube furnace. This was operated at the two prescribed temperatures, 650 oC and 825 oC, 

to generate well ventilated and underventilated conditions, respectively. In some tests, 

the air flow was increased or decreased by 30 %, the mass of the specimen was doubled, 

or the feed rate of the specimen through the furnace was increased by 50 %. In some of 

these combinations, the same fuel/air equivalence ratio was achieved under different 

combustion conditions. 

During each test, except for those in the tube furnace, the mass of the test specimen was 

monitored continuously. Each tube furnace specimen was weighed at the beginning and end of a 

test. The concentrations of CO2, CO, and O2 were monitored using species-specific analyzers. 

Fourier transform infrared (FTIR) spectroscopy was used to monitor CO2, CO, HCN, HCl, NO, 

NO2, H2CO (formaldehyde), and C3H4O (CH2=CH-CH=O, acrolein). The uncertainties in the 

measurements are discussed in the cited reports. For all the gases except CO2 and CO, many 

measurements were below or close to the limits of detection. The upper limits to the gas yields 

were calculated using the detection limits. 

The equations in ISO 13571 were used to estimate the relative contributions of these gases to the 

tenability of the fire environment. The results for each of the test series are presented in the 

individual reports. Further discussion is presented later in this report. Not surprisingly, the 

contribution of some of these gases to compromised tenability was of second order. This 

unimportance of secondary toxicants is consistent with the results of the animal experiments 

used to establish the N-gas hypothesis that attributes fire effluent lethality to a small number of 

gases.26 

7 
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8 
III. COMPILED DATA FROM ROOM- AND BENCH-SCALE TESTS 

As reported in each of the four testing reports, the gases for which yield data were analyzed were 

CO2, CO, HCl, HCN, NO2, NO, acrolein, and formaldehyde. The data for the last four gases 

were always below the limits of detection, and it is not possible to perform a quantitative 

comparison between the data from the combustible objects and specimens cut from them. 

Furthermore, their contributions to tenability were secondary to the contributions of the first four 

gases. (This takes into account the authors' position that incapacitating exposure to acrolein is 

properly reflected by the baboon smoke exposure data from the Southwest Research Institute.27) 

These results are not included in the compiled data tables below. 

Table 1 presents the notional, or maximum possible, yields of the four toxic gases for the roomscale and bench-scale tests. These were calculated as follows: 

 CO2: Assume all the carbon in the test specimen is converted to CO2. Multiply the 

mass fraction of C in the test specimen (Appendix A) by the ratio of the molecular mass 

of CO2 to the atomic mass of carbon. 

 CO: Assume all the carbon in the test specimen is converted to CO. Multiply the mass 

fraction of C by the ratio of the molecular mass of CO to the atomic mass of carbon. 

 HCN: Assume all the nitrogen in the test specimen is converted to HCN. Multiply the 

mass fraction of N by the ratio of the molecular mass of HCN to the atomic mass of 

nitrogen. 

 HCl: Assume all the chlorine in the test specimen is converted to HCl. Multiply the 

mass fraction of Cl by the ratio of the molecular mass of HCl to the atomic mass of Cl. 

The notional yields from the bookcase and cable specimens were assumed to be the same as the 

yields from the intact combustibles. The sofa specimen tests contained slightly different relative 

masses of fabric and foam. 

Table 1. Calculated Notional Yields of Toxic Products from the Test Specimens. 

Gas 

Notional Yields 

Bookcase Cable 

Sofa 

Room tests Bench-scale tests 

CO2 1.72 ± 1 % 2.11 ± 1 % 2.00 ± 4 % 1.95 ± 4 % 

CO 1.09 ± 1 % 1.33 ± 1 % 1.27 ± 4 % 1.24 ± 4 % 

HCN 0.057 ± 13 % 0.040 ± 6 % 0.193 ± 4 % 0.193 ± 4 % 

HCl 0.0026 ± 4 % 0.332 ± 1 % 0.0070 ± 19 % 0.0069 ± 19 % 

The uncertainty in the notional yield values is determined by the uncertainty in the prevalence of 

the central element (in the bullets just above) in the combustible. For the cuttings from the sofas, 

the uncertainty in the notional yields was increased by the small variability, estimated at 

3 percent, in the relative masses of the fabric and padding materials in the test specimen. 

Table 2 through Table 4 report the yields of these four gases as compiled from References 20 

and 22 through 25. Table 5 through Table 7 present the calculated fractions of the notional 

yields of the gases for the three types of specimens. The numbers in parentheses are the percent 

uncertainties. 

9 
Table 2. Yields of Combustion Products from Bookcase Specimens 

Test Type Test Variables 

Y

CO2 CO 

Room Ventilation 

Preflashover 0.50 

(50) 

2.4 x 10-2 (55) 

Postflashover 1.89 

(75) 

4.6 x 10-2 (30) 

Closed room --- --- 

Radiant furnace 

O2 initial Specimen 

0.21 intact 0.88 (8) 1.8 x 10-2 (40) 

0.21 diced 0.91 (8) 1.7 x 10-2 (15) 0.17 Intact 0.84 (8) 1.8 x 10-2 (8) 0.17 diced 0.76 (8) 2.1 x 10-2 (14) 

Smoke density chamber 

Irradiance (kW/m2) Pilot 

50 unpiloted 0.20 (48) 7.3 x 10-2 (40) 50 piloted 1.06 (12) < 4 x 10-4 25 piloted --- --­ 

Tube furnace Temperature Specimen Air flow Mass loading Mass feed rate 

650 oC (well ventilated) 

intact 1 1 1 1.43 (3) < 1 x 10-3 

diced 1 1 1 1.49 (5) < 1 x 10-3 intact x 1.3 1 1 1.66 (1) < 1 x 10-3 intact x2 x 2 1 1.58 (7) < 6 x 10-4 intact x1.5 1 x 1.5 0.83 (11) < 8 x 10-4 

825 oC (underventilated) 

intact 1 1 1 0.36 (38) 6.2 x 10-2 (45) 

diced 1 1 1 0.29 (2) 4.0 x 10-2 (21) intact x 0.7 1 1 0.21 (9) 6.3 x 10-2 (21) intact x2 x 2 1 0.31 (10) 5.7 x 10-2 (16) intact x1.5 1 x 1.5 0.28 (8) 5.0 x 10-2 (9) 

Cone calorimeter 

Irradiance (kW/m2) Air Flow (L/s) 

O2 initial 

50 25 21 1.11 (2) 1.0 x 10-2 (8) 

18 1.10 (0.1) 1.3 x 10-2 (3) 16 1.06 (4) 1.9 x 10-2 (7) 

50 12.5 21 1.02 (1) 0.6 x 10-2 (3) 

16 1.03 (0.5) 0.9 x 10-2 (9) 14 0.93 (0.3) 3.2 x 10-2 (1) 

25 25 21 1.14 (1) 1.9 x 10-2 (20) 

18 0.89 (4) 2.3 x 10-2 (17) 16 0.85 (1) 2.7 x 10-2 (1) 
Table 3. Yields of Combustion Products from Sofa Specimens 

Test Type Test Variables 

Y

CO2 CO 

Room Ventilation 

Preflashover 1.59 

(25) 

1.4 x 10-2 (35) 

Postflashover 1.13 

(25) 

5.1 x 10-2 (25) 

Closed room (500 s) 0.92 (10) 3.6 x 10-2 (2) 

Radiant furnace 

O2 initial Specimen 

0.21 intact 1.68 (10) 2.8 x 10-2 (32) 

0.21 diced 1.66 (7) 3.4 x 10-2 (15) 

0.17 Intact 1.64 (8) 3.6 x 10-2 (14) 

0.17 diced 1.59 (8) 4.9 x 10-2 (26) 

Smoke density chamber 

Irradiance (kW/m2) Pilot 

50 unpiloted 1.65 (2) 1.9 x 10-2 (12) 50 piloted 1.33 (53) 6.6 x 10-3 (x2) 25 piloted 1.76 (60) 4.3 x 10-3 (34) 

Tube furnace Temperature Specimen Air flow Mass loading Mass feed rate 

650 oC (well ventilated) 

intact 1 1 1 1.87 (9) 2.6 x 10-2 (10) 

diced 1 1 1 intact x 1.3 1 1 0.91 (5) 2.3 x 10-2 (38) 

intact x2 x 2 1 0.66 (5) 1.0 x 10-2 (31) 

intact x1.5 1 x 1.5 0.79 (14) 0.3 x 10-2 (88) 

825 oC (underventilated) 

intact 1 1 1 0.56 (7) 1.43 x 10-1 (1) 

diced 1 1 1 

intact x 0.7 1 1 0.35 (10) 1.66 x 10-1 (4) 

intact x2 x 2 1 0.23 (18) 5.2 x 10-2 (65) intact x1.5 1 x 1.5 0.28 (7) 1.43 x 10-1 (10) 

Cone calorimeter 

Irradiance (kW/m2) Air Flow (L/s) 

O2 initial 

50 25 21 1.41 (2) 2.7 x 10-2 (2) 

18 1.46 (2) 3.5 x 10-2 (4) 16 1.41 (2) 4.4 x 10-2 (2) 

50 12.5 21 1.36 (3) 2.4 x 10-2 (1) 

16 1.38 (4) 3.5 x 10-2 (7) 14 1.39 (1) 3.3 x 10-2 (4) 

25 25 21 1.55 (6) 2.4 x 10-2 (1) 

18 1.33 (30) 2.9 x 10-2 (16) 

16 1.36 (51) 2.9 x 10-2 (15) 
Table 4. Yields of Combustion Products from Cable Specimens 

Test Type Test Variables 

Y

CO2 CO 

Room Ventilation 

Preflashover 0.12 

(45) 

5.5 x 10-3 (50) 

Postflashover 1.38 

(15) 

1.48 x 10-1 (15) 

Closed room --- --- 

Radiant furnace 

O2 initial Specimen 

0.21 intact 1.16 (10) 5.8 x 10-2 (7) 

0.21 diced 1.13 (7) 6.7 x 10-2 (15) 

0.17 Intact 1.05 (8) 6.2 x 10-2 (30) 

0.17 diced 1.24 (8) 7.3x 10-2 (20) 

Smoke density chamber 

Irradiance (kW/m2) Pilot 

50 unpiloted 1.12 (5) 3.0x 10-2 (8) 50 piloted 1.18 (5) 2.8x 10-2 (7) 25 piloted 0.77 (12) 1.2x 10-2 (17) 

Tube furnace Temperature Specimen Air flow Mass loading Mass feed rate 

650 oC (well ventilated) 

intact 1 1 1 1.43 (27) 8.8 x 10-2 (16) 

diced 1 1 1 1.33 (6) 9.1 x 10-2 (9) intact x 1.3 1 1 1.27 (5) 7.0 x 10-2 (10) intact x2 x 2 1 1.15 (6) 7.1 x 10-2 (9) intact x1.5 1 x 1.5 1.20 (2) 6.5 x 10-2 (2) 

825 oC (underventilated) 

intact 1 1 1 0.33 (12) 4.3 x 10-2 (14) 

diced 1 1 1 0.31 (11) 3.7 x 10-2 (10) intact x 0.7 1 1 0.22 (1) 9.8 x 10-2 (20) intact x2 x 2 1 0.41 (8) 5.2 x 10-2 (11) intact x1.5 1 x 1.5 0.49 (2) 9.0 x 10-2 (2) 

Cone calorimeter 

Irradiance (kW/m2) Air Flow (L/s) 

O2 initial 

50 25 21 1.04 (9) 5.4 x 10-2 (5) 

18 1.17 (3) 6.7 x 10-2 (4) 16 1.11 (7) 7.1 x 10-2 (11) 

50 12.5 21 1.02 (3) 5.0 x 10-2 (3) 

16 1.02 (3) 6.1 x 10-2 (3) 14 0.88 (6) 5.4 x 10-2 (10) 

25 25 21 1.13 (6) 5.1 x 10-2 (1) 

18 1.28 (4) 6.3 x 10-2 (7) 16 0.68 (6) 4.2 x 10-2 (6) 
Table 5. Fractions of Notional Yields of Combustion Products from Bookcase Specimens 

Test Type Test Variables 

Y

CO2 CO 

Room Ventilation 

Preflashover 0.29 

(50) 

2.2 x 10-2 (55) 

Postflashover 1.10 

(75) 

4.2 x 10-2 (30) 

Closed room --- --- 

Radiant furnace 

O2 initial Specimen 

0.21 intact 0.51 (9) 1.7 x 10-2 (40) 

0.21 diced 0.53 (9) 1.6 x 10-2 (15) 0.17 Intact 0.49 (9) 1.7 x 10-2 (9) 0.17 diced 0.44 (9) 1.9 x 10-2 (15) 

Smoke density chamber 

Irradiance (kW/m2) Pilot 

50 unpiloted 0.12 (50) 7.0 x 10-2 (40) 50 piloted 0.62 (13) < 4 x 10-4 25 piloted --- --- 

Tube furnace Temperature Specimen Air flow Mass loading Mass feed rate 

650 oC (well ventilated) 

intact 1 1 1 0.83 (4) < 1 x 10-3 

diced 1 1 1 0.87 (6) < 1 x 10-3 intact x 1.3 1 1 0.97 (2) < 1 x 10-3 intact x2 x 2 1 0.92 (8) < 6 x 10-4 

intact x1.5 1 x 1.5 0.48 (12) < 7 x 10-4 

825 oC (underventilated) 

intact 1 1 1 0.21 (40) 5.7 x 10-2 (45) 

diced 1 1 1 0.17 (3) 3.7 x 10-2 (22) intact x 0.7 1 1 0.12 (10) 5.7 x 10-2 (22) intact x2 x 2 1 0.18 (11) 5.1 x 10-2 (17) intact x1.5 1 x 1.5 0.16 (9) 4.5 x 10-2 (10) 

Cone calorimeter 

Irradiance (kW/m2) Air Flow (L/s) 

O2 initial 

50 25 21 0.65 (3) 0.9 x 10-2 (9) 

18 0.64 (1) 1.2 x 10-2 (4) 

16 0.62 (5) 1.8 x 10-2 (8) 

50 12.5 21 0.59 (2) 0.6 x 10-2 (4) 

16 0.60 (2) 0.8 x 10-2 (10) 

14 0.54 (1) 2.9 x 10-2 (2) 

25 25 21 0.66 (2) 1.7 x 10-2 (21) 

18 0.52 (5) 2.1 x 10-2 (18) 16 0.49 (2) 2.5 x 10-2 (2) 
Table 6. Fractions of Notional Yields of Combustion Products from Sofa Specimens 

Test Type Test Variables 

Y

CO2 CO 

Room Ventilation 

Preflashover 0.80 

(25) 

1.13 x 10-2 (35) 

Postflashover 0.57 

(25) 

4.0 x 10-2 (25) 

Closed room (500 s) 0.46 (11) 1.8 x 10-2 (3) 

Radiant furnace 

O2 initial Specimen 

0.21 intact 0.86 (14) 2.3 x 10-2 (36) 

0.21 diced 0.85 (11) 2.7 x 10-2 (19) 

0.17 Intact 0.84 (12) 2.9 x 10-2 (18) 

0.17 diced 0.82 (12) 4.09 x 10-2 (30) 

Smoke density chamber 

Irradiance (kW/m2) Pilot 

50 unpiloted 0.85 (6) 1.5 x 10-2 (16) 

50 piloted 0.68 (60) 5.3 x 10-3 (x2) 25 piloted 0.90 (65) 3.5 x 10-3 (40) 

Tube furnace Temperature Specimen Air flow Mass loading Mass feed rate 

650 oC (well ventilated) 

intact 1 1 1 0.96 (13) 2.6 x 10-2 (10) 

diced 1 1 1 --- --- 

intact x 1.3 1 1 0.47 (9) 1.9 x 10-2 (40) 

intact x2 x 2 1 0.34 (9) 8.1 x 10-3 (35) 

intact x1.5 1 x 1.5 0.41 (18) 0.2 x 10-3 (90) 

825 oC (underventilated) 

intact 1 1 1 0.29 (11) 1.15 x 10-1 (5) 

diced 1 1 1 

intact x 0.7 1 1 0.18 (14) 1.3 x 10-1 (8) 

intact x2 x 2 1 0.12 (22) 4.2 x 10-2 (70) intact x1.5 1 x 1.5 0.14 (11) 1.12 x 10-1 (14) 

Cone calorimeter 

Irradiance (kW/m2) Air Flow (L/s) 

O2 initial 

50 25 21 0.72 (6) 2.2 x 10-2 (6) 

18 0.75 (6) 2.8 x 10-2 (8) 16 0.72 (6) 3.6 x 10-2 (6) 

50 12.5 21 0.70 (7) 1.9 x 10-2 (5) 

16 0.71 (8) 2.8 x 10-2 (11) 14 0.71 (5) 2.7 x 10-2 (8) 

25 25 21 0.79 (10) 1.9 x 10-2 (5) 

18 0.68 (35) 2.3 x 10-2 (20) 16 0.70 (55) 2.3 x 10-2 (20) 
Table 7. Fractions of Notional Yields of Combustion Products from Cable Specimens 

Test Type Test Variables 

Y

CO2 CO 

Room Ventilation 

Preflashover 5.7 x 10-2 (45) 4.1 x 10-3 (50) 

Postflashover 0.65 

(15) 

1.11 x 10-1 (15) 

Closed room --- --- 

Radiant furnace 

O2 initial Specimen 

0.21 intact 0.55 (12) 4.4 x 10-2 (8) 

0.21 diced 0.54 (12) 5.0 x 10-2 (16) 

0.17 Intact 0.50 (18) 4.7 x 10-2 (30) 0.17 diced 0.59 (12) 5.5 x 10-2 (20) 

Smoke density chamber 

Irradiance (kW/m2) Pilot 

50 unpiloted 0.53 (5) 2.3 x 10-2 (9) 50 piloted 0.56 (5) 2.1 x 10-2 (8) 25 piloted 0.36 (13) 0.9 x 10-2 (19) 

Tube furnace Temperature Specimen Air flow Mass loading Mass feed rate 

650 oC (well ventilated) 

intact 1 1 1 0.66 (28) 6.6 x 10-2 (17) 

diced 1 1 1 0.63 (7) 6.8 x 10-2 (10) intact x 1.3 1 1 0.56 (6) 5.3 x 10-2 (11) intact x2 x 2 1 0.55 (7) 5.3 x 10-2 (10) intact x1.5 1 x 1.5 0.57 (3) 4.9 x 10-2 (3) 

825 oC (underventilated) 

intact 1 1 1 0.16 (13) 3.2 x 10-2 (15) 

diced 1 1 1 0.15 (12) 2.8 x 10-2 (11) intact x 0.7 1 1 0.10 (1) 7.4 x 10-2 (21) intact x2 x 2 1 0.19 (9) 3.9 x 10-2 (12) intact x1.5 1 x 1.5 0.23 (3) 6.7 x 10-2 (3) 

Cone calorimeter 

Irradiance (kW/m2) Air Flow (L/s) 

O2 initial 

50 25 21 0.49 (10) 4.1 x 10-2 (6) 

18 0.55 (4) 5.1 x 10-2 (5) 16 0.53 (8) 5.4 x 10-2 (12) 

50 12.5 21 0.48 (4) 3.7 x 10-2 (4) 

16 0.48 (4) 4.6 x 10-2 (4) 14 0.42 (7) 4.0 x 10-2 (11) 

25 25 21 0.53 (7) 3.8 x 10-2 (2) 

18 0.61 (5) 4.7 x 10-2 (8) 16 0.32 (7) 3.1 x 10-2 (7) 
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16 
IV. ANALYSIS 

The test methods are evaluated following the criteria in ISO 2990312 and ISO 16312.28 There are 

additional considerations that reflect the use of the output data in fire hazard and risk analyses. 

A. FIRE STAGES 

Fires are generally turbulent diffusion flames. The fires that pose a threat to life safety involve 

flames that extend over large areas of the combustible item(s). For a single value of the global 

equivalence ratio, local equivalence ratios can vary considerably, i.e., the oxygen availability is 

different at various locations along the fuel surface. The combustion products measured 

downstream from a fire, whether well ventilated, or ventilation limited, are integrated over a 

range of equivalence ratios. 

Ideally, the combustion and/or pyrolysis conditions in the combustor section of a bench-scale 

apparatus reproduce the conditions in one or more stages of actual fires. The specimens should 

thus be burned under relatively constant, pre-selected conditions of thermal insult and oxygen 

availability (ventilation). 

This work focused on the three flaming stages that were identifiable from the room tests: well 

ventilated, vitiated preflashover (sofa material only), and postflashover. A pre-appraisal of how 

the four bench-scale apparatus related to these is as follows. 

	 At the beginning of a test in either of the two closed-chamber tests (radiant furnace and 

smoke density chamber), the oxygen volume percent is that of fresh air, and the test 

specimen is exposed to an external radiative flux of 50 kW/m2 . These conditions are 

similar to the well ventilated fire stage in the room tests, although the irradiance might be 

somewhat higher in the bench-scale test. The flames were laminar. During a test, the 

radiant flux was constant, but the oxygen volume percent declined to approximately 17 

percent to 18 percent. Accordingly, tests were performed at an initial oxygen level of 17 

volume percent (or lower) and an irradiance of 25 kW/m2 (smoke density chamber only) 

to determine sensitivity to these parameters. 

	 The tube furnace standard explicitly defines operating conditions for two fire stages, 

simulating well ventilated combustion with a peak furnace temperature of 650 °C and an 

equivalence ratio below 0.75, and underventilated combustion with a furnace temperature 

of 825 °C and an equivalence ratio of 2.0. These correspond to radiation temperatures of 

40 kW/m2

 and 80 kW/m2 . The lower irradiance only is a little high for well ventilated 

burning, and the higher irradiance is not unreasonable for postflashover burning. 80 

kW/m2

 is very high for the irradiance in the vitiated preflashover (closed room) scenario. 

	 The cone calorimeter can normally only simulate well ventilated combustion. However, 

we added an enclosure and gas delivery system to allow oxygen levels as low as 14 

volume percent to attempt to simulate postflashover combustion. 

The effects of these measures will be discussed in the analysis of gas yields below. 

B. APPLICABILITY 

All three of the finished products are layered and thus non-homogeneous. The radiant apparatus, 

the smoke density chamber, and the cone calorimeter are all designed to accommodate this 

17 
complexity of test specimen. In all three apparatus, the heat is applied radiatively to the top 

surface, as would be the case in a flaming environment. 

The tube furnace standard is limited to testing of homogenous materials. Thus, the inclusion of 

this apparatus in this project is an exploration. The heat to the specimen is applied to all 

surfaces, unlike the other three methods and unlike most fire environments. 

The outer layer in each of the three types of test specimens is not designed to protect the interior 

layer from thermal stress. If the outer layer had such a purpose, some additional consideration 

would be needed for the specimen design in the tube furnace, since the specimen is heated on all 

sides, and the sample boat is not very deep. 

As an initial step in assessing the importance of preserving the (nonprotective) layered structure 

of products, specimens were constructed to the dimensions prescribed by the standards. The 

same mass of specimen was then cut into small pieces and combusted. 

The specimens in the small-scale apparatus were cut from the same products tested in the room 

tests. Thus, any differences in yields can be attributed to the differences in the specimen 

preparation and the combustion environments. The specimens in the radiant apparatus, smoke 

density chamber, and cone calorimeter are similar to each other and to a portion of the 

combustibles in the room tests. Thus, good agreement among the yields can be attributed to 

similarity, or offsetting dissimilarities, in simulating any of the three fire stages. The bookcase 

and sofa material test specimens in the tube furnace are quite different; good agreement among 

the yields can be attributed to independence of the test specimen conformation and similarity of 

the combustion conditions, as well as any offsetting dissimilarities. 

C. APPARATUS INDEPENDENCE 

Each of the four apparatus designs might have some effect on the nature and concentrations of 

the gases reaching the analyzers. 

For all the bench-scale tests, the flame shapes and/or the flow fields differ significantly from 

those in the room tests. In none of the four apparatus does the flame from the specimen rise 

unperturbed to a height where all chemical reaction has ceased. 

	 In the smoke density chamber and the cone calorimeter, the upward flow is channeled 

through the conical heater. Some of the buoyant flow is close to the heater surface 

which, at an irradiance of 50 kW/m2

, is at approximately 700 C. 

	 In the radiant apparatus, the buoyant plume rises through a chimney, which is narrower 

than the opening in the conical heaters but is not as hot. 

	 The flame in the tube furnace extends horizontally and immediately impinges on the top 

surface of the tube, the temperature of which varies with the location along the tube and 

the intensity of the burning of the test specimen. The inlet air flow is uniform through a 

test, but the oxygen volume fraction in the downstream flame zone is determined by the 

oxygen that is unconsumed as it flows over the burning specimen and also the degree of 

mixing downstream of the specimen boat. 

In three of the apparatus (excluding the cone calorimeter), the product gases are sampled from a 

collection chamber. There is thus time for the gases, especially HCl, to adsorb on soot or walls. 

18 
In all four apparatus, the gases are sampled through heated lines. We did not insert a filter in the 

sampling lines in order to eliminate this possible source of perturbation. 

For the two closed chamber apparatus, the test duration is longer than the flaming portion of a 

test. For the radiant furnace, to abate the inclusion of post-flaming (oxidative pyrolysis) gas 

generation, we modified the procedure to cease irradiation and isolate the specimen from the 

sampling chamber once flaming ended. For the smoke density chamber apparatus, this isolation 

is not possible, and significant CO was generated postflaming. Also in these two apparatus, the 

recirculation of gas that had been passed through cold traps (necessary to protect the fixed-gas 

analyzers) as well as wall loses could potentially lead to a measurable decline in HCl as the test 

progresses. This is also true for the tube furnace, since the gas sampling is from a relatively 

small collection chamber. 

Given these dissimilarities, it was not assured that any of the bench-scale apparatus would 

demonstrate a high degree of replication of the yields of combustion products from the room 

tests. 

D. OPERATIONAL EFFICIENCY 

All of the apparatus were simple and capable of safe operation. 

E. DATA GENERATED 

All four methods allow for recording gas volume fractions using NDIR for CO2 and CO, 

paramagnetic oxygen analysis, and FTIR for CO2, CO, HCN, HCl, NO, NO2, acrolein, and 

formaldehyde. For the cone calorimeter, the time delay between gas generation and gas 

measurement is essentially the travel time through the sampling line. For the other three 

apparatus, the sampling of the gases from the respective collection chambers imposes a time 

averaging function on the measured results. The procedure for the tube furnace directs that gas 

sampling begin when steady state burning has been achieved. With all four apparatus, we began 

sampling before the test specimen was ignited or exposed to a heat source. 

The volume fractions of the gases were used to calculate yields using chamber volumes or gas 

flows and the mass lost by the specimen. The radiant furnace, smoke density chamber, and cone 

calorimeter included real time mass measurement, whereas the mass loss of a specimen in the 

tube furnace was measured by weighing before and after the test. Although none of our recent 

tests included bioassays, all four apparatus are adaptable for either direct exposure or extractive 

sampling. 

F. ACCURACY OF THE PHYSICAL FIRE MODELS 

When comparing the room-scale and bench-scale test results, it must be remembered that the 

current status of computational fire modeling does not include reliable prediction of the yields of 

the product gases. Prediction of the solid fuel gasification rate, the composition of the 

pyrolyzate, the potentially changing chemistry of the fuel (and thus the pyrolyzate) during a fire, 

and the conversion of the pyrolyzate to toxic combustion products are all the subjects of current 

research. Thus, the yields of the product gases are inputs to the models. As a result, predicting 

whether a fire environment is tenable or the time at which occupants become incapacitated 

19 
depends on the accuracy of the input yields. This, in turn, depends on the accuracy of the 

physical fire model used to generate those yields. 

In the following sections, unless otherwise noted, each yield comparison is between the room test 

value and the value from a standard operating condition for a bench-scale test. 

1. CO2 

a. Room Tests 

The CO2 yield is the link between the mass burning rate and the overall formation of combustion 

products. In a computational fire model, the concentrations of all of the other toxic species 

depend on the mass burning rate. It is therefore of prime importance to examine CO2 generation 

in the room fire tests. 

If a heated test specimen pyrolyzes without changing the elemental composition of the 

condensed residue, and if the carbon in the pyrolyzate is subsequently fully oxidized, the 

calculated yield of CO2 should equal the notional yield. This was generally not the case for the 

products examined here. 

For the room-scale cable tests, the preflashover CO2 yields were well below 10 percent of the 

notional yield. There were clearly some regions of the post-fire residue that were no more than 

copper wire and a tarry black residue, indicating a substantial change in the organic composition. 

Other regions were unburned. During the early burning, it is likely that the plasticizer was 

volatilized without efficient burning. (The smoke yield was approximately 0.2.) In addition, it is 

likely that HCl was emitted during pyrolysis of the PVC. These two processes would have 

substantially decreased the mass of the residue while generating no CO2 and may well account 

for the very low preflashover CO2 yield. 

Following flashover, the more vigorous burning increased the CO2 yield, and the measured 

postflashover CO2 yield was approximately two-thirds of the notional value. The smoke and CO 

yields were each a little over 0.1, so the carbon is accounted for, within experimental uncertainty. 

The CO2 yield from the postflashover portion of the bookcase tests was close to the notional 

yield. The soot yield was low, and the flaming was very vigorous. For the preflashover portion 

of the tests, the CO2 yield was approximately one-third of the notional yield. The flames were 

not particularly vigorous or spatially extensive, so it is reasonable that much of the pyrolyzate 

was not oxidized. 

The preflashover CO2 yields from the sofa tests were just below the notional yield, and the 

smoke yields were approximately 0.2. Postflashover, the CO2 yields were approximately onehalf of the notional value. The yields from the closed room tests were similar to the 

postflashover results, suggesting that vitiation reduced the completeness of combustion. 

b. Radiant Apparatus 

The CO2 yields for the bookcase material from the radiant apparatus were not very sensitive to 

the variation in initial oxygen volume fraction and whether the specimens were diced or intact. 

All the yield values were close to one-half the notional value. All the yields were high for the 

20 
preflashover phase of the room fire tests and somewhat low (but within the large variability of 

the room tests) for the postflashover case. 

For the sofa material specimens, the CO2 yields were about 15 percent lower than the notional 

yield, regardless of the variation in initial oxygen mole fraction and specimen conformation. 

The agreement with the preflashover room fire CO2 yield was excellent. The bench-scale yields 

were almost 50 % higher than the postflashover or closed room values. 

The CO2 yields from the cable material specimens also did not vary with initial oxygen mole 

fraction and specimen conformation. The values were in agreement with the postflashover room 

fire value. The forced combustion in the bench-scale tests did not reflect the lightly burning 

conditions in the preflashover room tests, with the bench-scale value overpredicting the room fire 

yield by an order of magnitude. 

c. Smoke Density Chamber 

For the smoke density chamber, the piloted, 50 kW/m2 exposure generated CO2 yields that 

agreed within the experimental uncertainty with the postflashover yields for all three types of 

specimens and the closed room yields for the sofa specimens. The unpiloted 50 kW/m2

 values 

for the bookcase and sofa materials captured the essence of the preflashover results within the 

experimental variability. None of the bench-scale operating conditions led to agreement with the 

preflashover CO2 yields from the cable materials. Under three of the nine combinations of 

apparatus conditions and test specimen, the repeatability of the CO2 yields was distinctively 

poor, relative to measurements made with the other three physical fire models. 

d. Tube Furnace 

Under the standard 650 oC exposure corresponding to well ventilated combustion, the tube 

furnace greatly overpredicted the preflashover CO2 yield from the bookcase (x 3) and cable (x 

10) materials, while properly predicting the preflashover CO2 yield from the sofa materials. 

Changing the mass and air flow conditions, but maintaining the same global equivalence ratio, 

led to severe underprediction of the preflashover yield for the sofa specimens and no 

improvement for the cable or bookcase materials. 

Under the intact specimen and standard 825 oC exposure corresponding to underventilated 

combustion, the CO2 yield was within experimental uncertainty of the postflashover room yield 

for the bookcase specimens, although the repeatability for both data sets was quite poor. (The 

mean values were a factor of 5 apart.) The yield was approximately a factor of two lower than 

the yields from the postflashover and closed room tests for the sofa materials, and was a factor of 

4 lower than the postflashover cable yield. Varying the test conditions did not substantially 

improve the agreement with the room test yields. 

e. Cone Calorimeter 

The examined variations in the radiant flux, air flow, and oxygen volume fraction (down to 0.14) 

did not alter the general consistency with the room fire test yields. For the bookcase materials, 

the bench-scale yields overpredicted the preflashover yield and underpredicted the postflashover 

yield. The prediction of the preflashover and postflashover yields from the room sofa tests was 

within experimental repeatability. The underprediction of the postflashover cable tests was just 

outside experimental repeatability. The preflashover CO2 yield from the room cable tests was 

greatly overpredicted. 

21 
 

 

 

 

 

 

 

 

 

 

f. Summary 

Table 8 summarizes the findings for the comparison of CO2 yields (in Tables 2 through 4) from 

the various bench-scale tests under their standard operating conditions relative to the room test 

results. "Good" means that the agreement is within the repeatability of the tests. "Low" and 

"high" indicate disagreement up to approximately ± 50 %. "Very high" and very low" indicate 

disagreement larger than approximately a factor of two. An asterisk (*) indicates that the basis 

for the rating is that the repeatability of the room data is ± 50 % or worse. 

The rows marked "Better" are for identifying varied apparatus conditions where the agreement 

for all three types of specimens is improved. For the CO2 yields, none of our variations resulted 

in improvements that allowed movement from one agreement designation to a superior one. 

Table 8. CO2 Yields from Bench-scale Tests Relative to Yields from Room Tests. 

Bench-scale Test and 

Conditions 

Room Test Result 

Preflashover Postflashover Closed Room 

Radiant apparatus 

Standard Bookcase: good* 

Sofa: good 

Cable: very high 

Bookcase: good* 

Sofa: high 

Cable: good 

Bookcase: ---

Sofa: high 

Cable: ---

Better None None None 

Smoke Density Chamber 

 50 kW/m2

, piloted Bookcase: high* 

Sofa: good 

Cable: very high 

Bookcase: good* 

Sofa: good 

Cable: good 

Bookcase: ---

Sofa: good* 

Cable: ---

Better None None None 

Tube Furnace 

650 oC, standard Bookcase: very high 

Sofa: good 

Cable: very high 

650 oC, better None 

825 oC, standard Bookcase: very low* 

Sofa: low 

Cable: very low 

Bookcase: ---

Sofa: low 

Cable: ---

825 oC, better None None 

Cone Calorimeter

 50 kW/m2

, 25 L/s Bookcase: high* 

Sofa: good 

Cable: very high 

Bookcase: good* 

Sofa: good 

Cable: good 

Bookcase: ---

Sofa: high 

Cable: ---

Better None None None 

2. CO 

Pitts' analysis of well ventilated compartment fires indicates that CO yields should be very low 

and rise sharply as the fuel/air equivalence ratio approaches unity. Near a ratio of 1.5, the CO 

yield reaches a plateau.29 A compilation of postflashover CO yields14 shows that the yield of CO 

22 
 

from postflashover room fire tests of a variety of combustibles is 0.2 ± 0.09. This results from 

vitiation (and thus truncation of the fuel oxidation process) in the upper layer of the burn room. 

In our room-scale tests, the CO yields were somewhat lower than this. Our hypothesis is that 

since the postflashover portion of those tests had visible flames coming out the door, that hot 

effluent was reigniting on contact with fresh air, and that this was causing some of the CO to 

oxidize, reducing its yield as measured further downstream. The recommendation was that a CO 

yield of 0.2 be used in fire hazard calculations, being indicative of the established conservative 

value. In the following, all bench-scale values are compared with this postflashover value of 0.2. 

None of the test methods consistently found postflashover CO yields near 0.2. The tube furnace 

generated the nearest yield for the sofa materials with the standard underventilated operating 

condition (825 oC). However, these results greatly overpredicted the CO yield from the closed 

room, which is also an underventilated fire test. 

The CO yields from the radiant apparatus predicted the preflashover yields from the bookcases 

and sofa materials within experimental repeatability, but severely overpredicted the yield from 

the cable arrays. None of the variations in operating conditions improved the agreement 

substantially. 

The CO yields from the smoke density chamber, operated at 50 kW/m2

 with a pilot flame, 

greatly overpredicted the preflashover yields from the cable arrays , but severely underpredicted 

the yields from bookcase materials and was consistent with the sofa fires due to very poor 

repeatability in the bench-scale data. At the same irradiance but unpiloted, this apparatus 

overpredicted the preflashover bookcase and cable yields and agreed with the sofa yield. Both 

the piloted and unpiloted results substantially underpredicted the closed room CO yield from the 

sofas. 

The tube furnace, operated under the standard well ventilated operating condition (650 oC), 

severely underpredicted the preflashover bookcase yield, predicted the yield from the 

preflashover cable fires (with help from a large variability in the room data), and overpredicted 

the preflashover yield from the sofa fires. Increasing the air flow (decreasing the global 

equivalence ratio), or increasing the mass loading while keeping the global equivalence ratio 

unchanged, led to improved agreement with the sofa and cable yields. Increasing the mass feed 

rate, which should be equivalent to increasing the mass loading, deteriorated the agreement with 

the sofa yield. 

The cone calorimeter, which is generally regarded as overventilated when operated at 50 kW/m2 

and 25 L/s, generated low CO yields for the bookcase materials, while generating high CO yields 

for the sofa and cable materials. Reducing the radiant flux to 25 kW/m2

 improved the agreement 

for the bookcase specimens, but not the cable and sofa materials. This brought all the yields to 

within about a factor of two agreement with the preflashover CO yield. However, at this heat 

flux, a number of materials do not ignite repeatably (or at all), making this an unsuitable 

operating condition for standard testing. 

Table 9 summarizes the findings for the comparison of CO yields from the various bench-scale 

tests under their standard, or chosen (by us), operating conditions relative to the room test results 

(preflashover or closed room) or a postflashover yield of 0.2. "Good" means that the agreement 

is within the repeatability of the tests. "Low" and "high" indicate disagreement up to 

approximately ± 50 %. "Very high" and very low" indicate disagreement larger than 

approximately a factor of two. An asterisk (*) indicates that the basis for the rating is that the 

23 
 

 

 

 

 

 

 

 

 

 

repeatability of the room data is ± 50 % or worse. A double asterisk (**) indicates that the basis 

for the rating is that the repeatability of the small-scale data is ± 50 % or worse. 

The rows marked "Better" are for identifying varied apparatus conditions where the agreement 

for all three types of specimens is improved. For the CO yields, none of our variations resulted 

in improvements that allowed movement from one agreement designation to a superior one. 

Table 9. CO Yields from Bench-scale Tests Relative to Yields from Room Tests. 

Bench-scale Test and 

Conditions 

Room Test Result 

Preflashover Postflashover Closed Room 

Radiant apparatus 

Standard Bookcase: good 

Sofa: good 

Cable: very high 

Bookcase: very low 

Sofa: low 

Cable: very low 

Bookcase: ---

Sofa: good 

Cable: ---

Better None None None 

Smoke Density Chamber 

 50 kW/m2

, piloted Bookcase: very low 

Sofa: good* 

Cable: very high 

Bookcase: very low 

Sofa: very low 

Cable: very low 

Bookcase: ---

Sofa: very low 

Cable: ---

Better None None None 

Tube Furnace 

650 oC, standard Bookcase: very low 

Sofa: good 

Cable: very high 

650 oC, better None 

 825 oC, standard Bookcase: good 

Sofa: very high 

Cable: very low 

Bookcase: ---

Sofa: very high 

Cable: ---

825 oC, better None None 

Cone Calorimeter

 50 kW/m2

, 25 L/s Bookcase: low 

Sofa: high 

Cable: very high 

Bookcase: very low 

Sofa: low 

Cable: very low 

Bookcase: ---

Sofa: low 

Cable: ---

Better None None None 

3. HCl 

If a test specimen burned completely and at steady state and if there were no wall losses, the HCl 

yield would equal the notional yield for the tests of the bookcase and sofa materials. For the 

cables, there is sufficient calcium in the jacket and insulation to bind only approximately onefourth of the chlorine. Thus, calculated yields of HCl that are substantially different from the 

notional yields reflect deviation from one or more of these conditions. 

The mass fractions of chlorine in the bookcases and sofas were very small, 0.3 % and 0.7 %, 

respectively. For nearly all of the bench-scale tests, the concentrations were below the detection 

24 
limits. Otherwise, the low concentrations of HCl resulted, in most cases, in high variability in 

the calculated yields. 

None of the calculated HCl yields or upper limits to the HCl yields from the radiant apparatus or 

the smoke density chamber was as large as the HCl yields measured in either the preflashover or 

postflashover stages of the room fire tests or these two products. For the bookcase specimens 

tested in the tube furnace and the cone calorimeter, the upper limits to the HCl yields approached 

the preflashover and postflashover values from the room fire tests. However, this is not 

sufficient to constitute agreement. For the sofa specimens, the HCl yields from these two 

apparatus were far smaller than the preflashover yield from the room tests. The upper limits to 

the HCl yields from the cone calorimeter approached the measured postflashover yield. 

The upper limits of the HCl yields measured in the tube furnace, smoke density chamber, and 

cone calorimeter were generally higher than the calculated yields from the closed room sofa 

tests, disabling any basis for comparison. The yields from the radiant apparatus, whether 

calculated or upper limits, were not inconsistent with the closed room value, but did not enable a 

clear comparison. 

The chlorine content of the cable materials was considerably higher than in the other materials. 

Nonetheless, the preflashover HCl yield from the room fire testing was quite low, approximately 

one-fiftieth of the notional yield. The yields from all four apparatus were all substantially higher 

than this. The radiant apparatus and cone calorimeter yields agreed with the postflashover yields 

from the room tests. The smoke density chamber and the tube furnace simulating 

underventilated conditions, underpredicted the postflashover yields. The tube furnace showed 

good agreement with the postflashover room fires when operated at the well ventilated 

conditions. 

Table 10 summarizes the findings for the comparison of HCl yields from the various bench-scale 

tests under their standard operating conditions relative to the room test results. "Good" means 

that the agreement is within the repeatability of the tests. "Low" and "high" indicate 

disagreement up to approximately ± 50 %. "Very high" and very low" indicate disagreement 

larger than approximately a factor of two. "Ind" indicates that the result of the comparison is 

indeterminate, generally because the yield from the room tests is lower than or comparable to the 

upper limit for the bench-scale tests. An asterisk (*) indicates that the basis for the rating is that 

the repeatability of the room data is ± 50 % or worse. 

The rows marked "Better" are for identifying varied apparatus conditions where the agreement 

for all three types of specimens is improved. For the HCl yields, none of our variations resulted 

in improvements that allowed movement from one agreement designation to a superior one. 

25 
 

 

 

 

 

 

 

 

 

 

Table 10. HCl Yields from Bench-scale Tests Relative to Yields from Room Tests. 

Bench-scale Test and 

Conditions 

Room Test Result 

Preflashover Postflashover Closed Room 

Radiant apparatus 

Standard Bookcase: very low 

Sofa: very low 

Cable: very high 

Bookcase: very low 

Sofa: very low 

Cable: good 

Bookcase: ---

Sofa: ind 

Cable: ---

Better None None None 

Smoke Density Chamber 

 50 kW/m2

, piloted Bookcase: very low 

Sofa: very low 

Cable: very high 

Bookcase: very low 

Sofa: low 

Cable: low 

Bookcase: ---

Sofa: ind 

Cable: ---

Better None None None 

Tube Furnace 

 650 oC, standard Bookcase: good 

Sofa: very low 

Cable: very high 

650 oC, better None 

 825 oC, standard Bookcase: ind 

Sofa: very low 

Cable: low 

Bookcase: ---

Sofa: ind 

Cable: ---

825 oC, better None None 

Cone Calorimeter

 50 kW/m2

, 25 L/s Bookcase: ind 

Sofa: very low 

Cable: very high 

Bookcase: ind 

Sofa: ind 

Cable: good 

Bookcase: ---

Sofa: ind 

Cable: ---

Better None None None 

4. HCN 

In general, concentrations of HCN were challenging to quantify, as it has relatively weak IR 

absorption and is a contributor to incapacitation within 5 minutes of exposure at concentrations 

that are only a few times its limit of detection with this FTIR spectrometer. 

HCN was quantified from all of the specimens at the room scale. HCN was not detected in any 

of the bench-scale tests of the bookcase materials, was only detected in the radiant apparatus for 

the cable specimens, and was detected in all bench-scale apparatus for the sofa materials. 

For the sofa materials, the yields from the radiant apparatus were in good agreement with the 

preflashover and closed room yields, but lower than the postflashover yield. Reducing the initial 

oxygen concentration had no discernible effect on the HCN yield. The upper limits of the yields 

from the smoke density chamber tests indicated that far less HCN was formed than in the room 

tests. 

26 
In the tube furnace, operation under the standard well ventilated operating condition (650 oC) but 

with a 30 percent reduction in equivalence ratio led to good agreement with the preflashover 

HCN yield. The standard underventilated operating conditions led to an HCN yield smaller than 

the postflashover yield, but substantially higher than the closed room yield. Variation in the 

operating conditions did not add additional information. The standard cone calorimeter values 

were in good agreement with the preflashover yields and higher than the closed room yields. 

They were lower than the postflashover yield, although reducing the oxygen volume fraction at 

full air flow and radiant flux increased the yield to a value approaching the postflashover yield. 

For the bookcase materials, the upper limits to the yields from the radiant apparatus were all 

smaller than the preflashover and postflashover yields. The upper limits from the smoke density 

chamber were substantially lower than the postflashover yields from the room tests. The upper 

limits to the tube furnace and cone calorimeter HCN yields did not allow for comparison with 

room test yields. 

For the cable materials, the yield from the radiant apparatus was much higher than the 

preflashover yield from the room tests and comparable to the postflashover yield (due in part to 

the poor repeatability of the bench-scale data. Reducing the initial oxygen volume fraction to 

0.17 reduced the HCN yield by an order of magnitude, making it far lower than the room fire 

yields. The yields from the smoke density chamber and the tube furnace were much lower than 

the postflashover room fire yields. The upper limits of the HCN yields from the cone 

calorimeter were far higher than the postflashover room fire yields. 

Table 11 summarizes the findings for the comparison of HCN yields from the various benchscale tests under their standard operating conditions relative to the room test results. "Good" 

means that the agreement is within the repeatability of the tests. "Low" and "high" indicate 

disagreement up to approximately ± 50 %. "Very high" and very low" indicate disagreement 

larger than approximately a factor of two. "Ind" indicates that the result of the comparison is 

indeterminate, generally because the yield from the room tests is lower than or comparable to the 

upper limit for the bench-scale tests. An asterisk (*) indicates that the basis for the rating is that 

the repeatability of the room data is ± 50 % or worse. A double asterisk (**) indicates that the 

basis for the rating is that the repeatability of the small-scale data is ± 50 % or worse. 

The rows marked "Better" are for identifying varied apparatus conditions where the agreement 

for all three types of specimens is improved. For the CO2 yields, none of our variations resulted 

in improvements that allowed movement from one agreement designation to a superior one. 

5. HBr and HF 

None of the combustibles contained Br or F, and therefore we have no data on their 

corresponding irritant gases. 

6. NO2, Acrolein and Formaldehyde 

None of these gases were detected in either the room-scale or bench-scale tests. 

In the room tests, the low preflashover concentrations of all the toxicants just outside the 

doorway indicate that effluent concentrations would not reach incapacitating levels outside the 

fire room. The maximum postflashover concentrations of NO2, acrolein, and formaldehyde that 

27 
 

 

 

 

could have been present would have made secondary contributions to incapacitation relative to 

the concentrations of HCl in the sofa and cable effluents. In the bookcase tests, where the HCl 

levels were low, the high postflashover levels of CO and HCN suggest incapacitation due to 

narcotic gases might occur for many occupants at exposure times of the order of a few minutes. 

This reduces the importance of these three gases (NO2, acrolein, and formaldehyde) in particular 

and irritant gases in general in causing incapacitation for these combustibles. 

In the cable effluent in all of the physical fire models, the contributions of these three gases to 

the total irritant FED was secondary to the HCl contribution. 22,24,25 In the effluent from the 

bookcase and sofa tests in all of the physical fire models (except the preflashover tests with the 

tube furnace), the high levels of CO lead to estimated incapacitation times of the order of 2 min. 

This suggests a secondary role for the irritant gases in causing incapacitation for these 

combustibles, as in the room-scale tests. 

Table 11. HCN Yields from Bench-scale Tests Relative to Yields from Room Tests. 

Bench-scale Test and 

Conditions 

Room Test Result 

Preflashover Postflashover Closed Room 

Radiant apparatus 

Standard Bookcase: very low 

Sofa: good 

Cable: very high 

Bookcase: very low 

Sofa: very low 

Cable: good** 

Bookcase: ---

Sofa: good 

Cable: ---

Better None None None 

Smoke Density Chamber 

 50 kW/m2

, piloted Bookcase: ind 

Sofa: ind 

Cable: ind 

Bookcase: very low 

Sofa: very low 

Cable: very low 

Bookcase: ---

Sofa: ind 

Cable: ---

Better None None None 

Tube Furnace 

 650 oC, standard Bookcase: ind 

Sofa: good 

Cable: ind 

650 oC, better None 

 825 oC, standard Bookcase: ind 

Sofa: low 

Cable: ind 

Bookcase: ---

Sofa: very high 

Cable: ---

825 oC, better None None 

Cone Calorimeter 

 50 kW/m2

, 25 L/s Bookcase: ind 

Sofa: good 

Cable: ind 

Bookcase: ind 

Sofa: very low 

Cable: ind 

Bookcase: ---

Sofa: high 

Cable: ---

Better None None None 

28 
 

V. RECOMMENDATIONS ON THE USE OF BENCH-SCALE APPARATUS FOR 

OBTAINING TOXIC GAS YIELDS FOR USE IN FIRE HAZARD AND RISK 

ANALYSES 

A. EFFECT ON HEAT RELEASE 

In fire hazard modeling, the composition of the fire effluent feeds into two types of calculations. 

Of initial importance is the heat release rate of the burning items, which determines both fire 

growth and the temperature of the fire environment. The heat release is the mass loss rate 

multiplied by an effective heat of combustion, ΔHeff. The total carbon in the effluent is a marker 

for the mass loss rate. The degree of accuracy of the total carbon yield is a determinant of the 

accuracy of the model's calculation of both heat release and effluent. In flaming combustion, 

most of the carbon appears as CO2, so modeling calculations of heat release are most sensitive to 

the yield of this gas. 

Table 12, compiled from Tables 5 through Table 7, summarizes the fractions of notional yields 

of CO2 from the room tests and from the bench-scale tests operated at their standard conditions. 

Table 12. Fractions of Notional Yields of CO2 in the Effluent from Fire Tests. 

Apparatus Test Conditiona Bookcase Sofa Cable 

Room Preflashover 0.29 (50)b 0.80 (25) 0.06 (45) 

Postflashover 1.10 (75) 0.57 (25) 0.65 (15) 

Closed room --- 0.46 (11) ---

Radiant furnace O2 volume fraction = 0.21 0.51 (9) 0.86 (14) 0.55 (12) 

Smoke density 

chamber 

50 kW/m2; piloted; 

O2 volume fraction = 0.21 

0.62 (13) 0.68 (60) 0.56 (5) 

Tube furnace 650 oC 0.83 (4) 0.96 (13) 0.66 (28) 

825 oC 0.21 (40) 0.29 (11) 0.16 (13) 

Cone calorimeter 50 kW/m2; air flow = 25 

L/s 

0.65 (3) 0.72 (6) 0.49 (10) 

a The conditions in the physical fire models are those in their respective standards, with delineation provided if a standard 

includes more than one operating condition. 

b

 The numbers in parentheses are the uncertainty percentages in the values. 

All four bench-scale apparatus, when operated under conditions that are expected to be reflective 

of well ventilated burning, generated similar fractional CO2 yields for the three types of test 

specimens. The values are consistent with (a) specimens that are being forced to burn and (b) 

allowances for CO and soot yields, some evaporated water, and enrichment of the carbon 

fraction in the residue (principally for the bookcase and cable materials). In the room tests, the 

combustible portion of the sofas burned efficiently before flashover, and as a result, the fraction 

of the notional CO2 yield is similar to the results from the bench-scale tests. For the other two 

combustibles, the mass loss was large compared to the mass of carbon that was oxidized. The 

early mass loss from the cable arrays was disproportionately from gasified HCl and plasticizer – 

29 
the flames were not steady and strong, and there was substantial tarry residue. The early burning 

of the bookcases was characterized by white smoke, indicative of gasified water and unburned 

organic molecules. Consistent with this, the shelves were significantly charred. 

After room flashover, all three combustibles burned vigorously. The fractions of notional CO2 

yields for the three types of test specimens are reasonable, given soot and CO yields that 

approached 0.3 of the notional carbon consumption. 

What was surprising was the low CO2 yields for all three types of test specimens burned in the 

tube furnace operating at the underventilated burning condition. We were unable to account for 

approximately two-thirds of the carbon. Qualitatively, there was no evidence in the FTIR spectra 

of large concentrations of gasified organic material, nor was there unusual residue in the 

downstream portion of the tube or in the collection chamber. The mass losses from the test 

specimens were close to the mass losses in the other three bench-scale apparatus. This an issue 

that merits further research. 

Nearly all the heat release results from oxidation of the carbon in the fuel to CO2 and the 

hydrogen in the fuel to H2O. With this large a discrepancy in the carbon balance, the calculated 

heat release from the fire would be in error, as will the resulting compartment temperatures. 

B. EFFECT ON TENABILITY CALCULATIONS 

There are two prime considerations in delineating a methodology for obtaining input data for 

toxic hazard modeling. The first consideration is the degree of accuracy that is sufficient for the 

purpose of the model. The needed accuracy is appropriately defined in terms of the acceptable 

uncertainty in the calculated times at which survival in a burning building is compromised. The 

consequences of assessments that err substantially in either direction were presented in the 

introduction to this report. 

There are many factors with large uncertainties that are encompassed in such a calculation, and it 

is both unfair and unrealistic to expect that the burden of precision should fall entirely on the 

assessment of toxic potency of the fire effluent. A more measured approach is as follows. 

A compilation of published animal exposure data30 found that the mean value of the LC50 of the 

smoke from a diverse group of materials and products was approximately 30 g/m3

 from well 

ventilated flaming combustion, about three-fourths of that for underventilated combustion, and a 

value in between for oxidative pyrolysis. The mean IC50 value was about 40 % of that range. In 

a building fire, all three processes are occurring simultaneously, so let us presume that the 

overall IC50 is approximately 10 g/m3 

. 

If the effluent from all burning items generated effluent with the same toxic potency, then it 

would be quite accurate to use this single value in a fire hazard or risk assessment. However, 

this compilation found common materials whose smoke toxic potency was up to five times the 

mean. There were also materials whose smoke toxic potency was as low as one-third the mean. 

The need in a fire hazard or risk analysis is to account for a combustible item whose smoke is of 

high toxic potency. This is significant if: 

	 the product of the combustible mass of the item and the toxic potency of the smoke is a 

sizable fraction of the summed (mass • potency) products for all the combustible items 

accessible to the fire, and especially 

30 
	 this product is unusually large for the first item ignited, such that it alone can result in a 

fire that threatens life safety. 

It follows that the calculation of the two components of toxic potency, the fractional effective 

dose (FED) due to inhalation of narcotic gases and the fractional effective concentration (FEC) 

due to exposure to sensory irritants, each be sufficiently accurate to identify significant 

deviations from "ordinary" toxic hazard. Given the current state of the art in fire modeling and 

the limits of precision of the IC50 data, it seems reasonable to ask that the accuracy be within a 

factor of two. 

The second consideration is the identification of a procedure for obtaining smoke toxic potency 

of that accuracy. In evaluation apparatus for this purpose, the accuracies of the yields of the 

toxic gases are not equally important. Due to the prevalence of fire deaths due to smoke being 

from postflashover fires11, a greater importance was attached to the postflashover gas yields. 

The yield of CO2 affects the carbon balance, and thus the relationship between the gas yields and 

the heat release. This, in turn, affects the calculated room temperatures and the burning rates of 

combustibles. It also exponentially increases a person's breathing rate and thus the volume of 

inhaled smoke. CO is an important toxicant in virtually all fires. When nitrogen is present in 

the fuel, it can also be a significant contributor to the FED. All three fuels in this study were 

nitrogen-containing, but HCN was only a contributor to the FED from the sofa materials. The 

cable was the only fuel that contained a high mass fraction of Cl, and HCl dominated the FEC. 

For the other two fuels, all the irritant concentrations were low, and tenability was dominated by 

the narcotic gases. 

The findings regarding the comparison between the gas yields from the room-scale tests and the 

bench-scale apparatus were as follows. 

	 CO2: The yields from apparatus A, B, and D were within experimental uncertainty of the 

postflashover room test yield and within a factor of 2 of the preflashover yield. 

The underventilated yield from apparatus D was low compared to the postflashover room 

value, and the well ventilated value was high relative to the preflashover room value. 

This may be indicative of the room yields being an average over a range of local 

equivalence ratios. 

The CO2 yields from all four apparatus agreed with the sofa material yield from the 

closed room tests to within a factor of 2. 

	 CO: None of the apparatus generated CO volume fractions comparable to the 0.2 value 

compiled from multiple series of postflashover room tests. 14 This is because the 

postflashover CO yields result from room conditions that are not readily replicated in a 

simple bench-scale device. The yield value of 0.2 should be used in hazard calculations. 

(This corrected value is contained in the standards for the radiant furnace.13,14) The yields 

from Apparatus A and D agreed with the preflashover room yield within a factor of 2. 

Decreasing the oxygen volume fraction to 0.16 in Apparatus D appears to have improved 

the agreement. A decrease in the oxygen volume fraction to 0.18 in Apparatus D led to 

agreement with the closed room yield. 

	 HCl: For the cable, the postflashover yields from Apparatus A and D were within 

experimental uncertainty. Decreasing the oxygen volume fraction in Apparatus D 

31 
degraded the agreement, but it was still well within a factor of 2. The yields from 

Apparatus B and C were not as good, but were still within a factor of 2 of the room test 

yield. 

The yields from all four apparatus were very high compared to the preflashover room test 

yield, which was a very low value. 

The upper limits of the HCl yields from the bench-scale tests of the sofa materials were 

too high for quantitative comparison with the very low yield from the closed room tests. 

	 HCN: The underventilated yield from Apparatus C tests of the sofa materials was within 

a factor of 2 of the postflashover room yield. The value from Apparatus D at an oxygen 

volume fraction of 0.21 was very low, but at a volume fraction of 0.16, the yield 

agreement was within experimental error. The values from the other apparatus were very 

low. The values for the sofa materials from Apparatus A, C, and D agreed with the 

preflashover room value within experimental uncertainty. 

The yields from the bench-scale tests of the sofa materials were within a factor of 2 of the 

closed room values for Apparatus A and D. The yield from Apparatus C operated at 

underventilated conditions was very high. 

As noted earlier, CO2 affects the narcotic gas potency by increasing respiration rate. It multiplies 

the contribution of CO and HCN by a factor of exp (volume % CO2/5). For the preflashover 

room fire tests, this factor is negligibly different from unity. Therefore, the effect of poor 

prediction of the CO2 by a physical fire model manifests only on the postflashover heat release 

rate (Section V.A.). 

For the postflashover fires, this respiration rate enhancement factor was as high as ten in the 

room fire test effluent. The CO2 yields from the radiant furnace, smoke density chamber, and 

cone calorimeter predicted the room fire yields almost to within experimental uncertainty. Using 

the tube furnace yields would introduce significant error into the exponential factor. 

C. RECOMMENDATIONS 

It should not be surprising that physical fire models, being imperfect approximations of some 

stage of real-scale burning, did not precisely predict the yields of multiple toxic gases from a set 

of diverse, non-homogeneous products that burned quite differently from each other. It should 

also not be surprising that under certain test conditions, the yields from both the room tests and 

the physical fire models showed large uncertainties. Nonetheless, one of the purposes of this 

project was to identify the more promising physical fire models to use for obtaining input data 

for fire hazard and risk analysis. The data indicate the following choices: 

Underventilated fires: 

	 The cone calorimeter operated at 50 kW/m2

 and a reduced oxygen volume fraction in the 

range of 0.16 to 0.18. 

Well ventilated fires: 

	 The cone calorimeter operated at 50 kW/m2 and an oxygen volume fraction of 0.21. 

None of the apparatus predict the HCl yield within a factor of two. 

32 
There are some recommendations regarding modifications to the standard operating conditions 

for these physical fire models. 

	 In all cases, the CO yields from the physical fire model should be adjusted to 0.2. 

	 In the radiant furnace, the shutter isolating the combustion chamber from the collection 

chamber should be closed immediately following the cessation of flaming. 

	 For the products examined, there was no sizable effect of cutting the specimens into 

small pieces. However, it is likely that the effect would be significant if some or all of 

the combustible mass were intentionally being protected by a fire barrier. 

	 The extensive ongoing research using various designs of the cone calorimeter with 

variable oxygen volume fraction and total inflow should include measurement of toxic 

species. This would further refine the operating conditions that provide the broadest 

agreement with the gas yields from room fire tests. 

Further investigation of the tube furnace is warranted. It is important to understand why the CO2 

yields for the underventilated condition are low and why the yields from the well ventilated 

condition are in agreement with the postflashover fire stages of the room fires for all three 

combustibles. It would also be helpful to understand the observed changes in some yields when 

the same equivalence ratio was achieved with different combinations of mass and air flow. 

The results of this study provide a better basis for obtaining toxic potency input data for fire 

modeling than currently exists. A more robust basis for future engineering assessments of fire 

safety designs would result from the performance of 

	 Additional room-scale tests with more combustibles and room placements. 

	 A series of parametric runs of a zone or field fire model in order to define better the effect 

of input data accuracy and variability on the times to threats to building occupant life 

safety. 

33 
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34 
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2 

. http://www.nist.gov/el/fire_research/cfast.cfm. 

3

. Peacock, R.D., Jones, W.W., and Reneke, P.A., “CFAST—Consolidated Model of Fire 

Growth and Smoke Transport (Version 6) Software Development and Evaluation Guide”, 

NIST Special Publication 1086, National Institute of Standards and Technology, 

Gaithersburg, MD, 187 pages (2008). 

4

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6. “Standard Test Method for Heat and Visible Smoke Release Rates for Materials and Products 

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9. “Life-threatening Components of Fire - Guidelines for the Estimation of Time to 

Compromised Tenability in Fires,” ISO 13571, International Standards Organization, Geneva, 

2012. 

10. "Guidelines for Assessing the Fire Threat to People," ISO 19706, International Standards 

Organization, Geneva, 2011. 

11. Gann, R.G., Babrauskas, V., Peacock, R.D., and Hall, Jr., J.R., "Fire Conditions for Smoke 

Toxicity Measurement," Fire and Materials 18, 193-199 (1994). 

12. "Guidance for Comparison of Toxic Gas Data between Different Physical Fire Models and 

Scales," ISO/FDIS 29903, International Standards Organization, Geneva, 2012. 

13. “Standard Test Method for Developing Toxic Potency Data for Use in Fire Hazard 

Modeling,” NFPA 269, NFPA International, Quincy, MA, 2007. 

14. “Standard Test Method for Measuring Smoke Toxicity for Use in Fire Hazard Analysis,” 

ASTM E1678-10, ASTM International, West Conshohocken, PA, 2010. 

15. Kaplan, H.L., Grand, A.F., and Hartzell, G.E., Combustion Toxicology: Principles and Test 

Methods, Technology Publishing Co., Lancaster, PA, 1983. 

16. "Guidance for Evaluating the Validity of Physical Fire Models for Obtaining Fire Effluent 

Toxicity Data for Use in Fire Hazard and Risk Assessment – Part 2: Evaluation of Individual 

Physical Fire Models," ISO/TR 16312-2, International Standards Organization, Geneva, 2007. 

35 
17. "Controlled Equivalence Ratio Method for the Determination of the Hazardous Components 

of Fire Effluent," ISO/TS 19700, International Standards Organization, 2010. 

18. "Plastics — Smoke Generation — Part 2: Determination of Optical Density by a Singlechamber Test, ISO 5659-2, International standards Organization, Geneva,1994. 

19. Babrauskas, V., Harris, Jr., R.H., Braun, E., Levin, B.C., Paabo, M., and Gann, R.G., "The 

Role of Bench-Scale Test Data in Assessing Real-Scale Fire Toxicity," Technical Note 1284, 

National Institute of Standards and Technology, 1991. 

20 (a) Gann, R.G., Averill, J.D., Nyden, M.R., Johnsson, E.L., and Peacock, R.D., “Smoke 

Component Yields from Room-scale Fire Tests,” NIST Technical Note 1453, National 

Institute of Standards and Technology, Gaithersburg, MD, 159 pages (2003). 

(b) Gann, R.G., Averill, J.D., Nyden, M.R., Johnsson, E.L., and Peacock, R.D., “Fire Effluent 

Component Yields from Room-scale Fire Tests,” Fire and Materials 34, 285-314 (2010), 

DOI: 10.1002/fam.1024. 

21. Ohlemiller, T.J., and Villa, K., “Furniture Flammability: An Investigation of the California 

Bulletin 133 Test. Part II: Characterization of the Ignition Source and a Comparable Gas 

Burner,” NISTIR 4348, National Institute of Standards and Technology, Gaithersburg, MD, 

1990. 

22. Gann, R.G., Marsh, N.D., Averill, J.A., and Nyden, M.R., “Smoke Component Yields from 

Bench-scale Fire Tests: 1. NFPA 269/ASTM E 1678,” NIST Technical Note 1760, National 

Institute of Standards and Technology, Gaithersburg, MD, 57 pages (2013). 

23. Marsh, N.D., Gann, R.G., and Nyden, M.R., “Observations on the Generation of Toxic 

Products in the NFPA/ISO Smoke Density Chamber,” Proceedings of the 12th International 

Conference on Fire Science & Engineering, (Interflam 10), Nottingham UK, (2010). 

24. Marsh, N.D., and Gann, R.G., “Smoke Component Yields from Bench-scale Fire Tests: 3. 

ISO 5660-1 / ASTM E 1354 with Enclosure and Variable Oxygen Concentration,” NIST 

Technical Note 1762, National Institute of Standards and Technology, Gaithersburg, MD, 43 

pages (2013). 

25. Marsh, N.D., Gann, R.G., and Nyden, M.R., “Smoke Component Yields from Bench-scale 

Fire Tests: 2. ISO 19700 Controlled Equivalence Ratio Tube Furnace” NIST Technical Note 

1761, National Institute of Standards and Technology, Gaithersburg, MD, 45 pages (2013). 

26. Babrauskas, V., Levin, B.C., Gann, R.G., Paabo, M., Harris, Jr., R.H., Peacock, R.D., and 

Yusa, S., Toxic Potency Measurement for Fire Hazard Analysis , NIST Special Publication 

827, National Institute of Standards and Technology, Gaithersburg, MD (1991). 

27. Kaplan, H.L., Grand, A.F., Switzer, W.G., Mitchell, D.S., Rogers, W.R., and Hartzell, G.E., 

"Effects of Combustion Gases on Escape Performance of the Baboon and the Rat," Journal of 

Fire Sciences 3, 228-244, (1985). 

28. “Guidance for assessing the validity of physical fire models for obtaining fire effluent 

toxicity data for fire hazard and risk assessment — Part 1: Criteria,” ISO 16312-1, 

International Standards Organization, Geneva, 2006. 

36 
29. Pitts, W. M., “Global Equivalence Ratio Concept and the Formation Mechanisms of Carbon 

Monoxide in Enclosure Fires,” Progress in Energy and Combustion Science 21, 197-237 

(1995). 

30. Neviaser, J.L., and Gann, R.G., “Evaluation of Toxic Potency Values for Smoke from 

Products and Materials,” Fire Technology 40, 177-200 (2004). 

37 
APPENDIX A. CHEMISTRY OF THE TEST COMBUSTIBLES 

Table 1. Elemental Analysis of Fuels. 

Mass % 

Sample C H N Cl Ca Pb Al Sb P Sn Ti Total 

Δ * 

Particle Board, with laminate 46.89 6.70 2.68 0.26 n n n n n n n 56.53 43.4

46.56 6.68 3.35 0.24 n n n n n n n 56.83 43.147.12 6.60 2.76 0.26 n n n n n n n 56.74 43.2

 Mean value 46.86 6.66 2.93 0.25 56.70 43.3 Standard deviation 0.28 0.05 0.37 0.01 0.15 0.1

Pressboard, with laminate 43.04 6.12 0.21 0.14 n n n n n n n 49.51 50.4

43.12 6.08 0.21 0.15 n n n n n n n 49.56 50.442.73 6.20 0.18 0.14 n n n n n n n 49.25 50.7

 Mean value 42.96 6.13 0.20 0.14 49.44 50.5 Standard deviation 0.21 0.06 0.02 0.01 0.17 0.1

Cushion fabric 47.23 6.23 0.18 n n n n n n n n 53.64 46.3

48.12 6.10 0.19 n n n n n n n n 54.41 45.5

47.38 5.99 0.20 n n n n n n n n 53.57 46.4

 Mean value 47.58 6.11 0.19 53.87 46.1

 Standard deviation 0.48 0.12 0.01 0.47 0.4

Cushion padding 56.38 8.48 12.58 0.95 n n n n 0.20 n n 78.59 21.4

56.33 8.58 12.50 0.90 n n n n 0.15 n n 78.46 21.5

56.36 8.53 12.46 0.71 n n n n 0.21 n n 78.27 21.7

 Mean value 56.36 8.53 12.51 0.85 0.19 78.44 21.5

 Standard deviation 0.03 0.05 0.06 0.13 0.03 0.16 0.1
Mass % 

Sample C H N Cl Ca Pb Al Sb P Sn Ti Total Δ * 

Cable jacket 40.83 5.07 <0.10 26.77 10.42 < 0.05 72.67 27.3

40.94 5.20 <0.10 26.53 10.18 < 0.05 72.67 27.3

40.87 5.15 <0.10 26.68 10.24 < 0.05 72.70 27.3

 Mean value 40.88 5.14 26.66 10.28 < 0.05 72.68 27.3

 Standard deviation 0.06 0.07 0.12 0.10 0.02 0.0

Wire insulation 48.25 6.73 2.39 26.04 0.80 0.62 83.41 16.5

48.20 6.98 2.65 26.08 0.81 0.62 83.91 16.048.57 6.82 2.40 26.22 0.72 0.63 84.01 15.9

 Mean value 48.34 6.84 2.48 26.11 0.78 0.62 83.78 16.2

 Standard deviation 0.20 0.13 0.15 0.09 0.04 0.00 0.32 0.3

Cable filler 42.58 6.65 <0.10 n 49.23 50.7

42.42 6.84 <0.10 n 49.26 50.7

42.72 6.80 <0.10 n 49.52 50.4

 Mean value 42.57 6.76 49.34 50.6

 Standard deviation 0.15 0.10 0.16 0.1

Cable residue 18.39 2.30 0.20 22.99 43.88 56.1

25.42 

19.03 2.45 0.21 27.76 49.45 50.5

28.62 

17.91 2.47 0.14 30.00 50.52 49.4

27.87

 Mean value 18.44 2.41 0.18 26.96 47.95 52.0

 Standard deviation 0.56 0.09 0.04 2.51 3.57 3.5

* [1 - Σ (mass %) of listed elements] 
Table 2. Elemental Analysis of Fuel Components. 

Mass % 

Sample C H N Cl Ca Pb Al Sb P Sn Ti Ash 

Wood 49.0 6.1 0.2 0.5 

Paper 49.0 6.1 0.2 0.5 

Urea formaldehyde 33.3 5.6 38.9 PVC 38.4 4.8 56.7 

Dioctyl phthalate 73.8 9.8 

Melamine 28.6 4.8 66.7 

Cotton ( = cellulose) 44.5 6.2 Polyethylene terephthalate 62.5 4.2 

Nylon 6,6 64 9.3 12 

Nylon 6 66 10.2 11 

FPU foam 57.6 5.6 11.2 

Table 3. Heats of Combustion of Fuels. 

Sample 

Δ

Hc (MJ/kg) Mean 

σ

Particle Board, with laminate 18.24 18.17 18.07 18.16 0.07 

Pressboard, with laminate 16.48 16.18 16.26 16.31 0.03 Cushion fabric 18.17 17.96 17.94 18.02 0.10 

Cushion padding 26.09 26.02 26.12 26.08 0.04 Cable jacket 18.30 18.41 18.36 18.36 0.04 

Wire insulation 23.39 23.33 23.45 23.39 0.06 Cable filler 17.01 17.00 17.00 17.00 0.00 Cable residue Did not ignite 
 

The mass fractions of cover fabric and padding in the sofa cushions were determined to be 

0.205 ± 0.004 and 0.795 ± 0.004, respectively. Since the cushions appeared to burn evenly (i.e., 

the fabric was generally not burned away well before the foam was) and since they were virtually 

consumed in the tests, we presumed that the elemental composition of the fuel was steady during 

the tests. We then estimated the cushion composition (mass fraction) to be: 

C: 0.545  1 % 

H: 0.080  1 % 

N: 0.100  1 % 

Cl: 0.0068  16 % 

P: 0.0015  17 % 

O: 0.267  4 % 

The derived value for the heat of combustion for the cushions is 24.4 MJ/kg  3 

For the bookcases, we estimated the fuel composition to be: 

C: 0.481  0.6 % 

H: 0.062  0.8 % 

N: 0.029  13 % 

Cl: 0.0030  4 % 

O: 0.426  1 % 

The heat of combustion for the bookcase is 18.2 MJ/kg  0.4 %. 

For the electric power cable, we measured the mass fractions of the insulation, filler paper, and 

jacket to be 0.516  0.007, 0.033  0.0007, and 0.239  0.007, respectively. The remainder of 

the mass was the copper wire. For the combustible material, the elemental composition was: 

C: 0.576  0.5 % 

H: 0.080  1.5 % 

Cl: 0.323  0.4 % 

N: 0.021  6 % 

The heat of combustion for the combustible fraction of the cable is 21.60 MJ/kg  0.6 %. 

41