[
The new British Standard 9999 fo fire safety in buildings is a leap
forward in fire safety but it still contains hidden dangers for both
firefighters and the public, according to a smoke control specilaist.
Jim Wild, a chartered engineer and associate of Manchester-based Fire
Engineering Associates, warns that although Section 28 recommends
properly designed and installed pressure differential systems for
firefighting shafts in buildings more than 30 metres high, and
basements more than 10 metres deep, it allows natural ventilation as an
alternative method in smaller commercial and residential buildings.
“And that’s where the danger comes in,” said Mr Wild. “Natural
ventilation systems have been around since 1971 and they have been
criticised from the beginning. The idea is to allow smoke to get into
the escape or entry route and then be ventilated … which is not a
good start.”
He says that natural ventilation is also very susceptible to external
wind conditions and research shows that, even with the very best
alignment of vent outlet with prevailing wind, smoke remained in the
escape routes on almost 50% of occasions. The recommendation that
natural vent outlets only be located where they are always subject to
negative wind pressures is very difficult, if not impossible, to
achieve in built up areas.
“For all these reasons firefighters could, even now, still find
themselves having to enter smoke-filled buildings – which is very
dangerous. It would have been safer if the new standard had excluded
this natural ventilation option altogether.”
Occupants of a building could be endangered, too, he adds, because BS
9999 does not clearly recognise that EN 12101 Part 6 also applies to
escape shafts.