ISO 13571-2012 pdf free download.Life-threatening components of fire – Guidelines for the estimation of time to compromised tenability in fires.
ISO 13571 is one of many tools available for use in fire safety engineering. Ills intended to be used in conjunction with models for analysis of the initiation and development of fire, fire spread, smoke formation and movement, chemical species generation, transport and decay, and people movement, as well as fire detection and suppression. This International Standard is to be used only within this context.
This International Standard is intended to address the consequences of human exposure to the life-threatening components of fire. The time-dependent concentrations of fire effluents and the thermal environment of a fire are determined by the rate of fire growth, the yields of the various fire gases produced from the involved fuels, the decay characteristics of those fire gases and the ventilation pattern (see A,1). Once these are determined, the methodology presented in this International Standard can be used for the estimation of the time at which individuals can be expected to experience compromised tenability.
With care, this guidance can also be applied to estimation of the time limit for rescuing people who are immobile due to injury, medical condition, etc.
This International Standard establishes procedures to evaluate the life-threatening components of fire hazard analysis in terms of the status of exposed human subjects at discrete time intervals. It makes possible the estimation of the time at which occupants can experience compromised tenability (see A.2). It enables estimation of a compromised tenability endpoint for each of the fire effluent components, with the most important endpoint being the earliest to occur.
Although the concept of compromised tenability is consistent with the definition of incapacitation (see ISO 13943), the latter term is not used in this International Standard due to its potentially broad interpretation to include many effects, including collapse and unconsciousness, that are not addressed. This International Standard focuses specifically on compromised tenability as influenced by both physiological and behavioural responses resulting from exposure to a fire’s life-threatening components.
The life-threatening components addressed include fire-effluent toxicity, heat, and visual obscuration due to smoke. In cases where the effluent composition is available, the toxic gas model is to be used for assessment of fire-effluent toxicity. For those cases where the effluent composition is unknown, an additional mass-loss model using generic toxic potency values is provided.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 13943, Fire safety — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13943 and the following apply.
3.1 tenability ability of humans to perform cognitive and motor-skill functions at an acceptable level when exposed to a fire environment
NOTE If exposed individuals are able to perform cognitive and motor-skill functions at an acceptable level, the exposure is said to be tenable. If not, the exposure is said to result in compromised tenability.
4 General princIples
4.1 Time to compromised tenability
The time to compromised tenability for individuals is the shortest of four distinct times estimated from consideration of asphyxiant fire gases, irritant fire gases, heat, and visual obscuration due to smoke.
The context and mechanisms of the fire-effluent toxicity component of life threat are discussed in Annex A. Effects of the asphyxiant toxicants, carbon monoxide and hydrogen cyanide (see A.3), as well as those of eye and upper-respiratory tract sensory irritants (see A.4), are described in detail.
Responses to these exposures involve functions of the human cardiovascular, respiratory and neurological systems that are dependent upon inherent physical characteristics (e.g., age, body weight, pre-existing cardiopulmonary conditions), along with environmental considerations and physical activity at the time of exposure. As a result, individual human responses can be highly variable and, therefore, not readily reduced to usable engineering equations for prediction of compromised tenability without considerable simplification, application of numerous assumptions, and exclusion of unusual circumstances.
With regard to the susceptibilities of individuals to the insults of fire exposure, a primary assumption of this International Standard is that all occupant responses are treated as an a priori log-normal statistical distribution with respect to a median time, with half of the population experiencing a tenable exposure and half experiencing compromised tenability (see 5.3). Other statistical distributions are possible, but in the absence of actual data. the log-normal is the most defensible.
4.2 Toxic-gas model
4.2.1 The toxic-gas models described in this International Standard address effects that are considered detrimental to human tenability. Because they are physiologically unrelated and mechanistically independent, asphyxiant toxicants and irritant toxicants are treated separately (see A.3 and A.4).
With irritant toxicants, only those that cause eye and upper-respiratory tract sensory irritation are considered in this International Standard as having effects on tenability (see A.4.2). Serious effects of pulmonary irritation are manifested from a few hours up to several days after exposure and are not normally expected to have a direct impact on tenability (see A.4.3).ISO 13571 pdf free download.