Fire Testing for Human Safety VICTOR A. DENSLOW Amoco Chemicals Corporation

The author proposes that more attention be given to human escape time -- the time between alerting and nonescape conditions and the comparison of available escape time to the needed escape time in real life situations.

I N RECENT years, an impressive amount of authoritative fire research has demonstrated how materials and products burn. Vast amounts of

data related to such physical effects as flame spread, rate of heat release, oxygen index, ease of ignition, mass burning rate, smoke development, tox- icity of gases, fire modeling, and fiashover are still being collected and analyzed. While these factors are important in the development of technology for reducing fire losses, an important link has been missing in the use of this type of information for reducing fire deaths and injuries; namely, consideration of human reactions and effects for direct assessments of human safety. There is increasing recognition that fire research has not adequately addressed itself directly to this issue, and, in fact, some research is underway. It seems timely to make specific proposals for bringing "people factors" to the forefront in research, in firesafety analysis, and in regula- tions and codes.

This paper is concerned with human safety and not directly with property damage, though there may be crossover benefits. Informal inquiries to numerous members of the fire community have indicated that human safety is, by far, their major concern. Subject to other opinions and/or to more for- real assessments, we will proceed on the basis that human safety is the primary goal. In any case, human safety concepts can stand alone in impor- tance and could be joined with property damage concepts to whatever degree the latter are, or become, important in assessing and regulating the fire environment.

F A T A L I T Y S T A T I S T I C S

Where can we most effectively attack the human safety problem and save the most lives? Fortunately, available statistics {Table 1} give us a clear answer. About 68 percent of fire deaths occur in one- and two-f~mily

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dwellings. By adding other human occupancies, such as transportation vehicles, apartments, institutions, offices, etc., we probably would find more than 80 percent of human deaths occurring in definable occupancies from fires originating in the structure or its contents. The concepts proposed herein apply to any occupancy and thereby relate to most of the human safety problem. One significant area to which these concepts may not apply directly, however, is the situation in which the first item ignited is clothing on a per- son.

TABLE 1. United States Fire Deaths by Occupancy

Occupancy Percen rage

Residential 68 Transportation 21 Industrial 3 Institutional, stores, offices 3 Others 5

Total 100%

Source: Highlights of Fire in the United States, NFPCA June 1978.

F I R E S A F E T Y T I M E L I N E

Our proposals evolve from a basic question, What is most important to a person in a place when a fire starts? What is important to you as you read this in a room or other enclosed place? We submit that it is a person's escape time. More specifically, it is the time interval between a person being alerted to the existence of the fire and the point at which escape is no longer possible. Further, it is important that the time needed for escape is not longer than the time available. Regardless of the flammability character- istics of the contents and surfaces of a room or space, the survival of oc- cupants is specifically dependent on time and human response and behavior under the particular conditions of the overall fire sequence involved.

This concept can be visualized by using a Firesafety Timeline, which starts at the first event in a fire sequence and continues until the end of events that affect human safety. I t indicates the times of human alert and escape limit, the available escape time, and the needed escape time. The timeline is specific for each space and also can be separately applied to spaces other than the space of fire origin. I t is also specific for each ignition sequence and configuration of furnishings.

IGNITION

The start of the fire sequence is the initial event in a real life accident. This could be the time at which a lighted match contacts something ig- nitable, a smoldering cigarette drops on a sofa or bed, electrical arcing or overheating begins, grease starts to overheat on a kitchen stove, or other such events occur. Note that the start of the sequence is not necessarily the point of flaming; smoking and smoldering can often give an alert long before

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Start of Escape fire sequence Alert limit

Time

LAvailable escape time ...... ~ "

~ Needed escape time--~l--~-----~ I Figure L Firesafety Tirneline.

flaming occurs. When this concept is considered in testing, it is important that ignition is not forced or contrived, but arises from probable cir- cumstances, so that a natural alert time and escape limit time can be established. Forced ignitions defeat any effort to realistically evaluate human safety.

ALERT TIME The time of alert in the timeline is significant as the beginning of escape

time. It is the point of initial human response and would normally involve one's seeing smoke, smelling smoke, feeling heat, hearing fire, and/or hear- ing an alarm or a warning from someone else. A person asleep presumably would be alerted somewhat later than a person who is awake. Any research or design work to shorten the alert time would usually provide more escape time, all else being equal. Smoke detectors are a prime example.

ESCAPE LIMIT The escape limit is the point at which conditions are such that a person

could no longer remove one's self or, if bedridden or nonambulatory, be removed from a lethal situation. This point on the timeline would indicate limiting toxic or heat effects and/or otherwise the foreclosing of all possible escape opportunities.

M E A S U R I N G S A F E T Y

The period between the points of alert and escape limit is the critical fac- tor to consider; it is the time available for an occupant to get out. The safety of a given occupancy would then be judged by comparing the time con- sidered to be needed for escape with the time available, as measured by test or otherwise determined, considering all factors. If only 10 s are needed to escape from a kitchen where smoking grease may allow up to 10 to 15 rain available escape time, it could be concluded that there is a low life risk from the grease and subsequent fire for a person in the kitchen. Fire statistics support this conclusion. If containers of flammable liquids in the kitchen were ignited, the available escape time might be only a few seconds, and the situation could be judged high hazard. Separate timelines and risk judgments would be made for people in rooms other than the kitchen.

The comparison of available escape time with the time needed for escape

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suggests judging safety by the amount of time available beyond what is needed. Values above 0 allow escape.

Avai lab le T ime - Needed T ime = S a f e t y Fac tor

Alternately, though possibly less useful, the ratio of the times could form a safety index. Values above 1.0 would allow escape.

Ava i lab le Time~Needed T ime = S a f e t y I n d e x

While this rather straightforward concept forms a working basis for judging acceptable risks for human safety in occupancies, there are numerous factors that need further investigation and development before the alert point and the escape Limit can be positioned on the timeline with precision or for the timeline to become useful in all cases. Note, however, that, where there is a large safety factor, the concept can be used now. These factors are (1) What alerts people, whether awake or asleep? (2) What in- capacitates people? (3) What escape time is needed for a particular enclosure? (4) How does human behavior affect needed escape time? (5) How do these factors vary for different categories of people? (6) What safety fac- tors are needed in judging acceptable risks? Specific numbers, measurable in testing, are needed in order to quantify these factors.

H U M A N R E S P O N S E R E S E A R C H

At least a start on research involving human response factors has been reported. The National Fire Protection Association's Research Division and the National Bureau of Standards have been studying people's behavior in fire situations. Others have reported various human and animal tolerance limits for fire gases and heat, some as a function of exposure time. Work is being done on identifying the gases and their concentrations that are pres- ent in real fires. Undoubtedly, there are other programs underway. This work is highly important for assessing human safety. Additionally, however, we would urge that it be directed toward the escape time concept so that it can be used in establishing the necessary points on the firesafety timeline. We need to establish physical values, measurable in fire tests, that alert people, awake or asleep. The work on incapacitation needs to be reduced to an agreed set of measurable values of the various effects that can be used to establish the escape limit. The work on human behavior should lead to, or at least be a part of, scenarios for establishing the time needed for escape.

In all of this work and in making acceptable risk decisions, it is impor- tant to accept the fact that there is no such thing as "zero risk." We will have fires. We will have deaths and injuries. This is the real world. Our first objective can only be to minimize them as much as is reasonably attainable. Thus, it is necessary to work in the realm of probabilities rather than the unattainable ideal of eliminating all risk from all possible fire situations. As noble as the latter goal appears, it can only handicap meaningful research and lead to impractical judgments. We should make use of fire statistics to

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determine the most important scenarios that cause human deaths and in- juries, and design our tests and safety judgments to have maximum, though not necessarily 100 percent, effectiveness. Such statistics have been developed by the National Bureau of Standards, the NFPA, and the U.S. Fire Administration and are being continuously updated.

FIRE TEST CRITERIA

At this stage of fire technology, it seems necessary to resort to large- scale testing of furnished rooms or other spaces in order to derive the kind of data required for these human safety concepts. So far, measurements known to be needed would be continuous plots against time of heat buildup, obscuration, and toxic gas concentrations at significant locations. The toxic conditions defining escape limit {tenability} have been proposed by various investigators and may need only minimal additional work to become accept- able to a consensus. However, criteria based on separate exposures to single effects cannot be assumed to reflect the real-life situation in which several effects occur at once, in sequences, and varying with time (e.g., heat, oxygen depletion, various gases, and obscuration). Thus, test animal ex- posures to full-scale burns may be necessary to establish real-life escape limit criteria. Likewise, criteria could be developed to establish conditions that would alert people. Again, it is most important to use natural or most probable ignitions rather than forced or contrived ignitions. As noted earlier, the alert time and sometimes even the escape limit time can be reached with smoldering or smoking before any flaming begins.

At this time, the small-scale tests for measuring flammability or fire gas toxicity properties of products and materials have apparently not, in- dividually or in combination, been specifically related to the alert, escape, and time factors involved in real-life human safety in actual occupancies, even though they obviously are indicators to some degree of fire progress and time factors. {Clothing fires and testing are considered to be a different type of problem.} Note, however, that the National Bureau of Standards is working toward that objective, and it is certainly to be hoped that small- scale test correlation with real-fire human safety will evolve in time, if for no other reason than to reduce the cost of testing. Other research programs are concerned with mathematically modeling fire progressions, using time to flashover as an important criterion, and toxicity evaluations. We would urge that human safety and escape time considerations be incorporated into the goals of all these research and testing programs. Such considerations should lead us to more directly reducing deaths and injuries, avoiding needless or misdirected regulations and building codes, and mM¢ing solu- tions to the problem more cost effective and more readily accepted.

C O N C L U S I O N

In summary, we propose that fire research add emphasis and priority to the following:

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• Injecting the Firesafety Timeline concept of available escape time compared to needed escape time into research and safety evaluations;

• Developing adequate cause and effect information on the human fac- tors involved in alerting, incapacitation, and the needed escape time;

• The use of full-scale tests for establishing basic human safety technical parameters;

• The correlation of small-scale testing with full-scale tests on the basis of human safety considerations; and

• Making judgments on the basis of saving lives and reducing injuries, rather than from mere burning tests or demonstrations.