One of the main causes of human losses in fires is the exposure to fire effluent: toxic gases, smoke and heat. As an alternative to prescriptive design, engineering firms use computational fire models to determine whether a planned building design will offer sufficient protection from effluent. Another useful application of such models is analysing how a fire that has already occurred led to injuries or deaths.
To be effective, explains Richard Gann, Chair of ISO/TC 92/SC 3, “These models need input data regarding the quantity and chemical nature of the effluent and the susceptibility of people to the effluent. Needless to say, the accuracy of these data is critical. For example, if the potency of the fire effluent is underestimated, people will not have time to survive. If the effluent input is too severe (too conservative), excessive money could be spent on unnecessary safety measures.”
The subcommittee has developed the world’s first set of standards needed by engineers to calculate how long a person has to escape from a burning building (or vehicle) when exposed to toxic and irritating gases, heat and vision-blocking smoke. “This has been an extraordinary process,” says Gann, “coordinating the contributions of the world’s relatively few multidisciplinary experts in fire science, toxicology, and chemical analysis.”
Most fire-effluent data is compiled from laboratory experiments in which materials and products are burned. This is where the ISO/TC 92/SC 3 standards play a crucial role, describing how to obtain yields of the fire-effluent components, characterize their effect on people who are exposed to them, and accurately represent the data.
The standards developed give safety engineers, regulatory officials and fire scientists the tools for evaluating the effects of fire on life, health and the environment. They:
- Define the context in which life safety in fires is to be evaluated
- Show how to analyse the gases from a fire or a fire test, and measure the smoke generated in a fire or lab test
- Describe how to determine the quality of effluent measurements from fire tests
- Provide equations for estimating when a person is incapacitated through exposure to heat, gases and visible smoke
- Propose a methodology for the analysis of the two principal toxic gases in the blood of victims and survivors
Large fires, such as those occurring in industrial plants, can also have severely harmful effects on the environment if the fire effluent is borne downwind, threatens population centres and persists in the surrounding flora, soil or groundwater. Addressing these hazards is also a key role of ISO/TC 92/SC 3. Some standards, for example, deal with what should be considered when determining the environmental impact of fires, while future documents will identify which fire gases to sample, where and how to sample them, and how to incorporate these data into fire models. The standards also provide important background information on how to contain contaminated water used in firefighting.
To date, ISO has published a total of 16 International Standards, technical specifications and technical reports within subcommittee ISO/TC 92/SC 3, and has a further nine documents under development. Close collaboration with ISO/TC 92/SC 4 on fire safety engineering and the Society of Fire Protection Engineers helps put these standards into practice, saving lives while keeping down the cost of construction.