There is clearly a role for statistical analysis of human size, speed of movement, sensory thresholds etc in the design of fire safety within buildings. Such considerations are already included in fire engineering to some extent. Whilst studies of population characteristics and related percentiles are of direct relevance and use in some aspects of fire safety design, they are of less or indirect relevance in others.
For example it is clear that tenability and toxicity limits in a fire engineered building must always exceed safe limits plus a safety margin for all occupiers- 100% of the population. It would be farcical to design CO levels at a toxic level for a percentage of the population during the evacuation phase. Statistical analysis will identify tenability limits. But levels of toxic substances this is of course interlinked to other factors that contribute to the evacuation time, and this is where an overall suitable safety margin will contribute to an acceptable level of safety.
In respect of means of escape, exit width calculations should be reviewed using statistical analysis taking account of the increased stature of the population since the Post War Building Studies were published. In order to set an appropriate percentile range, studies could be carried out across a range of occupancies. Height of doors is a less important factor for many reasons.
In many other aspects some degree of compromise is appropriate to ensure the provisions are reasonably practical. This includes fire alarm audibility, signage visibility, lighting levels. All these factors can reasonably be addressed in other ways for those who fall outside the percentile threshold.
All of the above needs to be balanced by a judgement on what Society will tolerate.
The hard bits include a detailed analysis of all human factors and a decision as to whether they have a direct bearing on fire safety through the ASET/ RSET approach.
For those that have only an indirect bearing (audibility of alarms, standard of lighting etc) an arbitrary percentile range could be set without danger knowing that the provisions for persons with special needs will provide a reasonable level of safety.
For those that have a direct bearing (escape route width for example) then it might be necessary to widen the percentile range based on intelligence linked to studies of occupancy types.
Finally for some factors (toxicity for example) only 100% plus a suitable safety margin will suffice.
Theres more to this than meets the eye once you start to think about it. Penny for your thoughts Colin?
