Numbers in the Fire Industry

31˚C - CO2’s critical point: the temperature at which CO2 turns totally from liquid to gas.

CO2 is permanently under 720 psi or 49 bar of pressure ie nearly 50 times atmospheric pressure (by comparison a cup of water at sea level exists at 1 bar or 14.5 psi). Its state changes under increased temperatures to one that is neither a liquid nor a gas.

50-55˚C   -  critical points of FM-200® and Novec™1230 (turning from liquid to gas).

Gases under pressure are often effectively considered by the industry as single and passive cylinder columns of solid material from the perspective of their monitoring following installation. Whereas being under pressure and constantly changing under temperature they should be considered as active and dynamic systems requiring constant monitoring. These are not passive systems therefore; they are dynamic ones, and all dynamic systems under pressure need constant monitoring.

14520 - the ISO standard regarding fire systems from installation with regard to room integrity through to maintenance and inspection of contents

ISO 14520-1:2015(E) specifically states in Contents Indication that - Means shall be provided to indicate that each container is correctly charged and in At least annually, or more frequently as required by the authority, all systems shall be thoroughly inspected and tested for proper operation by competent personnel. Under ISO 14520 where gaseous extinguishing systems have to be designed in relation to the discharging agent hold-time (if the room cannot hold the agent because of leaks the agent will disperse and not extinguish the fire) and discharging agent peak pressure (if the pressure is too high for partition walls or suspended ceilings they will be blown apart or damaged and possibly destroying the room integrity). At the design stage of a fire extinguishing system rooms are tested for room integrity by positively pressurising a room and detecting escaping pressure to verify that the room itself into which the gaseous extinguishant discharges on actuation can both hold the agent after its discharge and hold its pressure on actuation. The fire system is then installed and commissioned. However,  over the next 10 years no further tests are made on room integrity and the cylinders merely hydrostatically tested to ensure they can cope with their design pressure limits. How can one be sure therefore that on actuation the room will hold the discharged agent to extinguish the fire and its partitions and ceilings are capable of withstanding the pressure of the agent on discharge?

5% - loss of agent above which it is deemed unacceptable in liquefied gaseous extinguishing system and thus requires refilling. 10% - loss of pressure above which it is deemed unacceptable in liquefied gaseous extinguishing systems and thus requires refilling

The risks of accidental discharge or leakage is recognised within the regulations.  BS EN ISO 14520 -1:2015(E) reasonably assumes that the execution of its provisions is entrusted to people qualified and experienced in the specification, design, installation, commissioning, testing, approval, inspection, operation and maintenance of systems and equipment, and who can be expected to exercise a duty of care to avoid unnecessary release of extinguishant. The assumptions in the installation, commissioning and maintenance of gaseous extinguishing systems is that they are highly pressurised but risk leaking and discharging. The regulations that sensibly underpin this assumption aim to identify their leak identification at an interval of every 6 months. Cylinders accidentally discharge. CO2 can cause fatalities if it does. 1% of pressure gauges fail and 25% of valves too. Essentially, it is known in regulations that the gaseous systems leak and need to be maintained. Given that the gaseous systems are designed specifically to the individual need of that room, building e.t.c, then a 5% loss of agent may mean that they would not fully extinguish the fire. What if there are also leak sites in the room? The likelihood of the gaseous system effectively extinguishing the fire gets lower and lower.

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