DESCRIPTION AND APPLICATION

The Fire suppression systems with chemical gas HFC-227ea (FM200 tm) - Heptafluoropropane (CF3CHFCF3) are clean agent systems. They do not operate chemically on the flame but remove the heat of the flame through a physical cooling process.

This type of suppression system thanks to its reduced volatility and its environmental acceptability is much used in rooms with full saturation. In fact, as shown in the table below, extrapolating the NOAEL value at 9% in volume, the HFC-227ea is the best solution for man and environment.

Its functioning is based on the principle of total flooding; the great advantage is therefore that there is no need to worry about the location of the material to be protected or 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 required.

For a correct evaluation of the compatibility of HFC 227ea with the environment, the reaction between gas and the resulting burning products has to be taken into account. In fact fluoride acid (HF) in limited quantity can be produced and therefore the use of oxygen masks is suggested.

As for the concentration limits and people exposure to gas HCF-227, reference is made to the U.S.A. Environmental Protection Agency and to the Reinhardt Protocol.

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


The proliferation of clean agent suppression systems of the Halocarbons and inert gas type has caused 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 class A 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 HFC-227 gas 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.