Alarm time is the time at which occupants first become aware of a fire through a building’s automatic or manual fire alarm system (occupant notification). RSET is the sum of the alarm time, the evacuation delay time (sometimes called the pre-movement time), and the movement time. Carbon monoxide concentration must remain below 1,400 ppm.The temperature must remain below 65° C.Sample tenability criteria for determining ASET might be: The time at which conditions become untenable (ASET) is the time at which the amount of smoke or heat, as calculated by a fire model or similar tool, first exceeds pre-established tenability criteria. Next, this design fire is provided as input to a calculation tool such as a fire model to determine the time after ignition at which space through which occupants must pass becomes untenable due to the presence of smoke or heat. First, a design fire (heat release rate history) is established by considering the types of combustibles present and their associated product yields (primarily soot and carbon monoxide). A candidate design is acceptable if the ASET is greater than the RSET, after applying an appropriate safety factor.ĪSET is determined by applying empirical correlations or fire modeling. The Required Safe Egress Time (RSET) is the amount of time (also measured from fire ignition) that required for occupants to evacuate a building or space and reach the building exterior or a protected exit enclosure. The Available Safe Egress Time (ASET) is the amount of time that elapses between fire ignition and the development of untenable conditions. Comparison of Available Safe Egress Time (ASET)įor the performance-based design of smoke control systems, and atrium smoke control systems, in particular, an ASET/RSET analysis is usually conducted.
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