Carbon Dioxide (CO2) gas fire extinguisher

This extinguisher contains carbon dioxide stored as a liquid under high pressure. When the valve is opened the CO2 issues through the funnel as a gas which is heavier than air and tends to blanket the fire on to which it is directed. Air containing more than 17 per cent of CO2 does not support combustions although oxygen is still present.

The advantage of this type of extinguisher is that CO2 leaves no trace and does less damage by its impact than a liquid jet. It is therefore suitable for extinguishing small fires in laboratories and for dealing with burning liquids. It is a non-conductor of electricity.

The purpose of the discharge horn is to reduce the velocity of the gas so that it does not act like a blow torch and blow up the fire. It also prevents the entrainment of air with the CO2.

This extinguisher was manufactured in 1972 and has the advantage over earlier types that it is unnecessary to return it to the manufacturer for recharging immediately after use. The operating head is constructed in such a way that the exhausted cylinder can be removed and immediately replaced by a charged cylinder, so that it is ready again for service.