An Analysis of Factors Affecting Available Safe Escape Time

Abstract:

This paper deals with some of the parameters that affect the available safe evacuation time (ASET), including fire growth rate, enclosure area, and thermal properties of the bounding construction. Although the available safe escape time is a crucial design parameter, it is, or has to be, often generalised to cover a range of scenarios; this is also the case of design codes. It is therefore necessary to be aware in which aspects such generalisation is possible. A set of computer model cases, carried out in CFAST, is analysed and the effect of individual variables quantified. As real fires usually grow exponentially with time, the t²-fire model was used, employing the standard fire growth rates. By analysing the computer model scenarios, it was found that increasing the size of the enclosure does not bring proportional growth of available safe escape time. It is the rate of fire growth that is the primary factor affecting the safe available escape time. Two different smoke layer height tenability criteria – 0.9m and 1.5m – are also compared; the first derived from literature and the latter represent a more conservative estimate.

• Periodical: Advanced Materials Research (Volume 1001)
• Pages: 267-271
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.1001.267
• Online since: August 2014
• Authors: Vladimír Mózer*
• Keywords: Available Safe Escape Time (ASET), Compartment Size, Fire Growth Rate, Smoke Layer, Smoke Temperature

References

[1] PD 7974-6 Human factors: Life safety strategies (British Standard Institute, London 2003).

[2] STN 92 0201-3 Evacuation Routes and Evacuation of Occupants (SUTN, Bratislava 2000).

[3] NFPA 101 Life safety code (2009 edition), (NFPA, Massachusetts 2010).

[4] CLG. Approved Document B, vol. 2 2013 ed, (CLG, London 2013).

[5] NIST SP 1041 CFAST – Consolidated Model of Fire Growth and Smoke Transport (version 6) User's Guide, (NIST, Maryland 2008).

[6] NIST SP 1026 CFAST – Consolidated Model of Fire Growth and Smoke Transport (version 6) Technical Reference Guide, (NIST, Maryland 2009).

DOI: 10.6028/nist.sp.1026r2009

[7] C. Mayfield, D. Hopkin.: FB 29 – Design Fires for Use in Fire Safety Engineering, (BRE Trust, Watford 2011).

[8] PD 7974-1 Initiation and development of fire within the enclosure of origin (British Standard Institute, London 2003).

[9] J. Martinka, E. Hroncová, T. Chrebet, K. Balog.: Fire Risk Assessment of Thermally Modified Spruce in: Acta Facultatis Xylologiae Vol. 52(2) (2013), pp.117-128.

[10] J. Martinka, T. Chrebet, J. Kral, K. Balog.: An Examination of the Behaviour of Thermally Treated Spruce Wood under Fire Conditions in: Wood Research Vol. 58(4) (2013), pp.599-606.

[11] L.Y. Cooper.: A Mathematical Model for Estimating Available Safe Egress Time in Fires in: Fire and Materials Vol. 6(3-4) (1982), pp.135-144.

DOI: 10.1002/fam.810060307

[12] H. P. Morgan, et. al.: BR 368 - Design Methodologies for Smoke and Heat Exhaust Ventilation, (Construction Research Communications, Watford 1999).

[13] V. Reichel.: Zabraňujeme škodám 26 – Navrhování požární bezpečnosti výrobních objektů III., (Česká státní pojišťovna, Praha 1988).

[14] P.J. DiNenno (Ed. ) et al.: SFPE Handbook of Fire Protection Engineering (3rd ed. ), (Society of Fire Protection Engineers, Bethesda, MD 2002).