DESCRIPTION AND APPLICATION

The aerosol systems use a suspension of fine particles having the consistency of a very thin powder that is generally made of potassium nitrate.

These systems use in fact, in order to obtain the fire suppression, a chemical in addition to a physical inhibition mechanism.

The system of powder generation is actuated through aerosol generators, which are generally steel containers of various sizes. Through the internal combustion process activated by an ignition device and a subsequent freezing process created by magnesium which, owing to high temperatures (120°/130°), is transformed into magnesium oxide thus generating H2O, the aerosol suspension is released with a certain strength facilitating its dispersion.

The compound forming aerosol is classified as dangerous material "Class 4.1" under the Classification Code of Dangerous Materials of United Nations (ADR).

The systems are predominantly of two kinds, the first with local application, where generators are fitted in predetermined places so as to cover a well defined area, the second with total saturation where the generators are evenly spread within all the volume to be protected so as to obtain a more widespread effect.

At present the most used aerosol systems are the condensed ones, where the aerosol is generated by the controlled combustion of potassium in a special container, others called the dispersed ones, utilize already formed aerosol which is carried by a vector gas into the areas to be protected.

These systems are valid for fire suppression of class A and B in confined areas of small dimensions. A clear limitation to their use is due to present absence of technical legislation and to uncertainties connected to the potential toxicity of aerosol and to the concentration used for suppression.
Present regulations under study limit its use to non occupied areas.

The necessary tools for aerosol suppression systems are the following:

A manual deactivation system at the entrance of the protected area;
A sketch indication the place of manual release;
Exit routes always available;
Emergency lighting installation;
Self-locking doors;
Acoustic and visual alarms inside and outside the protected area;
Warning signals and safety instructions;
Automatic alarm before extinguisher release;
Forced ventilation devices to be activated after extinguisher release;
Instructions and personnel training including those carrying the maintenance.