The aim of foam rain systems is to tackle the fire with a mixture of water and foam, the type and proportions of which vary depending on the combustible material present, which is interposed between the combustible material and the combustion air (oxygen), thus extinguishing the flames by suffocation.
These systems are classified according to the ratio volume of the water-foam mixture before and after the generators / dispensers and may be
the low expansion type with expansion ratio of up to 1:20, medium expansion type with expansion ratio up to 1:200 or high-expansion type with expansion ratio up to 1:1,000.
The foaming agents used vary depending on the combustible material present and the type of foam system chosen.
The system is usually operated in connection with a detection system normally with smoke detectors or heat detectors.