It is possible to obtain information on fire spread as affected by the
attendance of the brigades from the statistics of the fires reported by the
fire brigades. The long term implication for building regulations of
these new uses of the statistioal data may be fundamental since at present
the requirements for the fire resistance of structures do not allow for the
presence of the brigade - i.e. they are based on burn out under free
burning. The paper describes the concepts employed, concepts which later
will be refined by relating them to a probabalistic model of fire spread.
Even without this, however, some interesting results can be obtained.
Firstly, the mean probability that a fire spreads out of a compartment
in a non-residential building is about 0.02 min^-1, the order of magnitude to
be expected where fire resistance is commonly 30 or 60 mins. Secondly, the
probability that fires in these buildings built since 1950 spread out of the
room of origin is virtually the same as for older buildings though there is
a lower chance of spreading upwards and a higher chance of spreading sideways.
Also an effect of attendance time differences on the chance of spread
has been found for at least one type of building.
