By Ken Hedjack
Our experience clearly proves that the best approach to extinguishing fires in buses is to use a water-based system as opposed to a dry powder system. Dry powder is sometimes used in fire extinguishing systems in buses or cars, but a water-based system is much more effective at quickly overturning the flame source and maintaining suppression. Any type of fire extinguishing system will initially drop the flame, but the key makes sure it stays suppressed.
Each type of thermal event has three elements: flame, oxygen and heat – the latter of which can cause spontaneous combustion. A water-based system attacks all three elements – eliminating the fuel source, the oxygen that feeds the flame and the heat source itself (which can, in many cases, lead to re-ignition). Water-based firefighting suppresses fire effectively and is also used to reduce temperatures and prevent regeneration.
A water-based system generates steam to kill the oxygen of the flame. This eliminates the heat source because water will touch a 600 degree fire, for example, and drop it to 100 degrees within seconds. Activation time (45 to 60 seconds) is critical in ensuring the possibility of repetition. This is a holistic view of putting out fires.
We also see advantages for mechanically based systems operated in the presence of a heat source, compared to systems operated by electronic signals. A heat-sensitive hose – installed in the engine compartment as well as in the battery compartment – explodes when it reaches a certain temperature, releasing pressure from the fire bottle and activating the nozzles / fog.
Many systems will also only run for a maximum of 15 to maybe 30 seconds, but we recommend running anywhere from 45 seconds to 60 seconds.
Many transportation providers feel they do not need a fire – until the moment they really need a fire. We must be prepared for when necessary. We carry the most expensive cargo on earth, and we must make sure we do everything possible to pay attention to each type of scenario. The actual cost of extinguishing the fire is minimal when taking into account the life cycle of a bus or coach. This is the right thing to do to get ready for that scary drawer.
Alternate propulsion and fire suppression
Firefighting comes down to the flammability of the fuel source. Diesel, gasoline and propane have different flash points. The lower the flame point, the greater the risk of fire – and propane and gasoline have much lower flash points than diesel.
Electricity is a new consideration for buses and United Safety will conduct significant research on electric fire extinguishing systems. We do know that the Federal Aviation Administration (FAA) has stated that water-based systems are best suited for fighting lithium-ion fires, but we need to do further research on where and how the all-electric bus should be protected.
The way forward
From a fire safety standpoint, nothing takes the place of an effective preventative maintenance program. From there, drivers must do a very thorough check daily before driving. This means not only checking the boxes and moving around in the vehicle, but actually looking for problems in the daily inspection.
Finally, when a fire extinguisher is installed on your vehicle, make sure that you conduct the correct annual inspections and intervals within the properly planned time frames. These requirements vary between firefighting systems, so make sure you meet the capabilities and requirements of your specific system.
The Hedgehog Nest Serves as National Sales Manager at United Safety. visit
www.unitedsafetycorporation.com Learn more.