Enclosure fires

Carbon monoxide (CO) is the next most common gas which
occurs, after carbon dioxide and water, and is very often the
main cause of death in fi res. This gas is highly combustible
and has a broad fl ammability range. CO is a colourless, odourless
gas, which makes it diffi cult to detect. Carbon monoxide
accumulates in large quantities when the ceiling material is
made of wood. A content level of 10–15% can be achieved.
The CO content can vary from 0% right up to 15% with
certain fuel arrangements. The CO content is critical at 1500
ppm, which is equivalent to 0.15% volume.
CO content % Harmful effect
0.1–0.12 Unpleasant after 1 hour (dizziness, head-aches)
0.15–0.2 Dangerous when inhaled for more than 1 hour
(paralysis, loss of consciousness)
0.3 Dangerous when inhaled for 1/2 hour
1.0 Lethal when inhaled for 1 minute
Hydrogen cyanide (HCN) is produced when products such as
wool, silk, nylon and polyurethane do not combust completely.
This gas is highly combustible and toxic, and can quickly
cause death by asphyxiation. It is colourless.
Nitrogen dioxide (NO 2) and other oxides of nitrogen are produced
in small quantities from fabrics and in large quantities
from materials such as viscose. Nitrogen dioxide causes severe
irritation to the lungs and can result in immediate death. It is an
odourless gas with, typically brown in colour. Hydrogen cyanide
and nitrogen dioxide are often formed at the same time.
Ammonia (NH 3) is produced when materials such as wool, silk
and nylon are combusted. The concentration levels are usually
low in the case of building fi res. Ammonia has a typical odour
and causes irritation in low concentrations. But it does not result
in death. Ammonia is colourless and is rarely produced in
concentrations which would pose a risk to people.
Hydrogen chloride (HCl) is formed during pyrolysis of certain
insulating materials for cables, such as PVC, as well as for
materials which have been treated with fi re retardants and
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