User Manual

34
Siemens Switzerland Ltd
Building Technologies Division
Figure 4.3.2-1 Principle of a gas extinguishing system
4.3.3. Fire extinguishers
Fire extinguishers are mobile or portable manual devices designed for preventing incipient stage fires from
getting out of control. The extinguishing agent is expelled under pressure. In some types of extinguisher the
agent is kept under constant pressure, while in others the pressure is generated by releasing a propellant gas at
the time that the extinguisher is activated.
Extinguishing agents include water, foam, carbon dioxide and powder. These substances function in different
ways and are suitable for different types of fires. Fires are categorized into five main fire classes A, B, C, D and F.
Fire class Description
A
Solid materials
Solid materials subject to thermal decomposition which normally for
members.
Examples: wood, paper, leather, textiles and coal
B
Liquids
Liquids or materials which melt under heat and only create flames.
Examples: alcohol, oil, wax, resin, paraffin, petrol, paints, tar and acetone
C
Gases
Gaseous materials which are often stored under pressure.
Examples: hydrogen, natural gas, acetylene, methane, ethane, propane and
butane
D
Metals
Strongly ember-forming, combustible metals.
Examples: aluminum, magnesium, potassium, sodium, beryllium, lithium
and barium
F
Cooking
oils
Combustible cooking oils and fats commonly found in commercial
kitchens.
Figure 4.3.3-1 Material fire classes