Extinction by gas or condensed aerosols?

26/11/2018
Joan Torres

The principal differences between installing the aerosol condensed extinguishing system or the gas, are that they are cheaper, easier to mount and occupy less space.

Gas extinguishments have been the most used, so far to protect all types of equipment, such as electrical panels, motors, server rooms, etc. The most commonly used are CO2, FM-200 and FE-13. The advantage of the last two, is that they do not leave residues, after extinction and they are not as harmful as CO2, for people. But in recent years, taxes have appeared that aggravate the application of certain gases that cause the so-called "greenhouse effect". For this reason, they began to replace them, either by the CO2 gas, the most economical, or by the inert gases.
The problem of gas extinctions is that their bottles, take up a lot of space, and the final customer, must always have a space, outside the area to be protected, for their placement. In addition to this, the pipes and accessories used must guarantee their correct distribution and withstand the high discharge pressure.

And now come, the condensed aerosols, a kind of extinction, largely unknown, but that offers clear advantages over gas extinctions. The only problem, but not least, is that they leave some residue, which, despite not causing direct damage, it is important that after an extinction, all areas susceptible to corrosion or electronic circuits, are well cleaned, since, depending on the area, the dust generated can trap the humidity of the environment, and cause certain damages.

There are several types of aerosols, the ones that reduce oxygen by inert gas, those that physically cool the fire and those that act chemically by removing the reactive free radicals. These last ones, are the ones that interest us most.

The condensed aerosols, are NOT pressurized equipment. The charge used for the extinction, is included in each "diffuser", and its dimensions depend on the amount of aerosol they contain. The more volume we want to protect, the more quantity of aerosol will be necessary. But if we have a small space, to place the aerosols, we can always choose to install smaller equipment until we reach the necessary amount. The aerosols can protect all types of fires A, B, C, F and even there are certain aerosols for the D (metallic).

For the calculation of the aerosols, it is basically required: the volume, the design density and the openings or ventilation.

m = ρ ∙ V

m            Amount of aerosol mass (g)

ρ             Density of the application (g/m3)

V             Volume to be protected (m3)

The design density is given by the same manufacturer. In case of openings or ventilation, if these cannot be closed or stopped, a safety factor must be applied, which guarantees a correct suppression.

The activation of the aerosol can be done electrically, with an extinguishing control unit with a fire detection, or directly by thermal fuse, either thermal cable or ampoules. In addition to these methods, the same aerosol acts autonomously when it reaches a temperature of 300°C.

Regarding maintenance, it should be done according to R.D. 513/2017 quarterly and annual revisions, checking only that the electrical parts work correctly. The equipment has a useful life, which depends on the manufacturer and the place where they are installed. But its lifespan, is usually between 15-25 years. What gives it a clear advantage over the gases, which every 10 years the bottles have to be hydrostatically tested.