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Fire Fighting Gases
CO2 – Carbon Dioxide / Chemical Description
Carbon Dioxide can exist in three states: as a Gas, a Liquid or Solid. At normal temperatures and
pressures, Carbon Dioxide is a colourless Gas with slightly pungent odour at high concentration.
Skin Contact
Carbon Dioxide cannot exist as a Liquid at atmospheric pressure. When Liquid under pressure is
released in the atmosphere, the discharge will consist of gas and solid only. It will appear as a dense
white cloud, due to the solid content and also the condensation of moisture from the atmosphere at
the low temperature obtained. The solid will fall to the ground as a flocculent snow. Direct contact with
solid Carbon Dioxide can give rise to severe frost burning and medical attention should be sought.
Spillages
Carbon Dioxide is not usually considered to be a toxic gas in the generally accepted sense of the term
(i.e. Poisonous) and is normally present in atmospheric air at the level of approx. 0.03% (300ppm).
The threshold limit value (TLV) for Carbon Dioxide is given in the Health and Safety executive
guidance note EH15/80 (threshold Limited Values 1980). The TLV is set at 0.5% by volume
(5,000ppm) as the maximum level that can be reasonably tolerated over an eight hour day. The same
value is quoted in the Health and Safety executive guidance note 40/85 (Occupational Exposure Limit
1985) as the long-term exposure limit. Cardiac or respiratory defects increase the hazards of
inhalation and brochitics should be careful to avoid heavy exposure. In the event of any doubt, the
TLV of 0.5% (5,000ppm) should be regarded as the maximum level of exposure for the individual
concerned. As the Carbon Dioxide concentration is increased beyond these limited levels, air is
displaced and there is therefore a corresponding reduction of the oxygen content in the atmosphere.
Inhalation stimulates respiration and may also produce mild narcotic effects. Breathing becomes more
laboured as the level is further increases and at very high concentrations, Carbon Dioxide can
paralyze the respiratory centre. The potential hazard of asphyxiation should, therefore, be understood
by personal handling of Carbon Dioxide and should be taken into account, particularly where there is
a possibility of high concentration accumulating in enclosed spaces.
However, since the gas is heavier than air, it will, in practice accumulate in higher concentrations at
the lower levels. It is therefore, possible for relatively ‘safe’ and ‘unsafe’ concentrations to be present
at the same time in the space concerned. In the event of accident or loss of consciousness and
unaccompanied person could fall to the floor and be exposed to high concentration for an extended
period before rescue. It is, therefore, advisable that a second person is present when an enclosed
space is entered in such circumstances.
Fire Division of the R-Gas Co. Ltd Company Registration
No. 3957147