DESCRIPTION AND APPLICATION

The Fire suppression systems with chemical gas HFC-23 (FE 13) - Trifluoroethane (CFH 3) are clean agent systems. The norm regulating this extinguisher is the NFPA 2001 , ISO 14520-10 and the UNI 10877/10.They do not operate chemically, but through a physiochemical thermal transfer so as to reduce the temperature of the flame at a level where combustion becomes impossible.

The principle of HFC-23 is the one of total flooding; the great advantage is therefore that there is no need to worry about the location neither of material to be protected nor of its shape because homogeneous conditions in all the room are created. As a result of the descending direction of the blend air- extinguishing agent, it is important to indicate the maximum height at which objects to be protected are placed.

Another essential parameter is the calculation of the total volume to be protected in order to fix the quantity of gas to be used. The specifications of the rooms to be protected are in fact essential for a valid planning of the equipment and in fact the NFPA norm requires the Door Fan Integrity Test; the closure of all the openings with automatic frames and the immediate stop of any ventilation system are fundamental for a good functioning of the system.

In particular places where various openings more or less sealed are present and from where the extinguishing gas can leak out, the method of double release is used. After a first release, a second one follows so as to keep the gas concentration at the parameters requested.

As for the concentration limits and people exposure to gas HFC-23 reference is made to the U.S.A. Environmental Protection Agency and to the Reinhardt Protocol.

For a correct evaluation of the compatibility of HFC-23 Gas with the environment, the reaction between gas and the resulting products has to be taken into account. In fact fluoride acid (HF) in variable quantity can be produced and therefore the use of oxygen masks is recommended.

Table A - Comparison between HFG-23 and HFC-227e properties


The proliferation of clean agent suppression systems of the Halocarbons and inert gas type has provoked the insertion of a new Protocol in the standard NFPA 2001 aimed to check the toxic compatibility and called PBPK- Physiologically Based Pharmacokinetic model which takes into account the maximum acceptance of the agent in the blood and the necessary time to reach it.

This extinguisher is particularly recommended for protection in rooms of classes containing combustible materials such as wood, paper, plastics etc. Typical installations are in data processing and telecommunication centres, museums and archives where high value objects are present.

The gas HFC-23 suppression system is made of pressurised storage containers (cylinders) connected through valves to a pipe network to send it to destination (collector and distribution pipes). At the end of it, the gas is released through engineered nozzles into the rooms to be protected.