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We have all seen films such as The
Towering Inferno of people escaping
through flames and thin smoke, but in fact
smoke is black, thick and pungent. We
have become more aware of the blindness,
dis-orientation and difficulties of breathing
caused by smoke, yet even this is a
massive understatement of the real killing
effect of smoke. The most efficient killers
are the release of carbon-monoxide and
lethal gases and oxygen depletion.
Carbon-monoxide is the most common
constituent of smoke. It is colourless,
odourless and deadly poisonous.
Concentrations as low as 1% in the
atmosphere can be lethal, leading to
disorientation in 20 seconds.,
unconsciousness in about 60 seconds and
death in about 90 seconds. It is a fallacy
that sleeping persons will wake from smoke
irritation. They die in their sleep.
Other poisonous gases are also present. |
For example, upholstery foam gives off
particularly dangerous gases such as
hydrogen cyanide and isocyanates that can
be absorbed even through the skin.
Oxygen at normal atmosphere is 20% and
this balance is critical for life support.
Respiration can no longer be sustained if
the level of oxygen falls to even 14%, so
danger immediately occurs in a smoke
filled, oxygen depleted atmosphere. |
A well made door assembly with substantial
door stops will allow in the region of 5-7
cubic metres of smoke to leak through per
minute. This can allow the entry of lethal
gases such as carbon-monoxide to reach
the critical 1% in as little as 20 seconds. A
set of our intumescent seals, with smoke
seal brushes, properly fitted, will eliminate
at least 96% of this smoke and it is unlikely
that concentrations of lethal gases or
oxygen depletion will reach critical levels.
If a cold smoke seal, such as our Brush
Seals or Medium Smoke Seal, such as
FP1212 is being used, a plain intumescent
strip is also recommended for hot smoke
control. |
