Fire Suppression Mitigates Evacuation Time

The most important thing to remember about fire suppression is that suppression is the operative term. If you apply enough heat to any vehicle or fuel, it will burn down regardless of an onboard extinguisher or fire suppression system. No onboard fire suppression system will be 100 percent effective at extinguishing fires 100 percent of the time – but the goal is to buy a bus or motorcoach driver more time to clear passengers from the bus during an emergency evacuation.

There is a lot of work for drivers evacuating riders after an accident, especially so in the wake of an active fire. A driver is not expected to extinguish the fire themselves – their priority is the riders. Fire suppression acts to give the driver as much time as possible to safely evacuate the vehicle.

Technology Advances Detection

We advocate for a nuanced approach to fire detection and suppression, largely due to Thermal Protection Service’s position as the only authorized distributor of Kidde Technologies fire suppression systems.

For dry agents, we suggest the use of a BC-rated Purple-K formula – a Kidde-specific compound – which coats a compartment entirely, and greatly reduces the chance of a reflash. The use of standard ABC dry chemical is also an industry best practice.

What really differentiates one fire suppression system from another is the detection technology. Furthermore, detection technology can be tiered depending on the budget and needs of an transit agency or over-the-road operator.

At the upper end of detection technology is a dual-band infrared optic sensor. Developed for the United States military, this “smart eye” sensor has a detection rate averaging less than one second. The eye is a resettable sensor with an LED status monitor for easy confirmation of system operability. We have seen more and more commercial ground vehicles opting for this level of fire detection in recent years.

Another available sensor is called an armored linear thermal detector (LTD). This is a wire cased in stainless steel sheathing, with a built-in melting point. When it detects a certain level of heat, the wire melts and activates the fire suppression system.

Below those, operators can also opt for a standard LTD at a lower price point due to the lack of steel sheathing – or for the even more affordable spot thermal detectors, which focus entirely on single-spot heat detection.

In many cases, an effective fire suppression system might extinguish a fire before it really starts. If the infrared sensor detects the fire in less than one second, there is a chance the operator will have no idea a fire even occurred. But even if you have a slower detector in the vehicle, and the fire actually does do damage to the drivetrain, then we are still buying the operator time to stop the bus and evacuate passengers.

Tackling New Power Systems

The advent of electric vehicles (EVs) is so new that data is still being collected on the best methods to fight lithium-ion battery fires. The most important element of these fires is monitoring the cells and their temperature. 

Ideally, the best way to detect a battery fire would be to monitor the interior of the battery box. However, because of proprietary information, battery manufacturers are not currently allowing this level of detection. The next best way to detect these fires is to monitor the cell’s exterior and provide an extinguishing agent to that exterior and all remaining systems. For now, that is the best method we have found to detecting and suppressing these fires.

System Upkeep

A preferred system should feature 24/7 self-monitoring capabilities. So, if there is ever an issue with the system, there will be an audible and visual alarm. In these cases, the system should need zero output from the driver.

In other cases, some agencies or operators might prefer a manual discharge button. For these types of systems, the agent will discharge automatically as well as after the driver pushes a button.

Proactive Fire Safety is Key

In an ideal world, buses do not simply catch on fire – fires arise due to other mitigating issues. Therefore, preventative maintenance (PM) is first and foremost in proactive fire safety. Oil leaks, exhaust leaks, or loose belts and hoses – all can be contributors to a vehicle fire. If you stay on top of PM, then you can feel confident in the remote monitoring and detection found in your fire suppression system – which typically only require a six-month visual inspection and six-year bottle service.

Matt Szymanski is director of operations at Thermal Protection Services (TPS). TPS is the only authorized distributor of Kidde Technologies Commercial Ground Vehicles genuine parts, field service, technical and warranty support, and customer training in North America. Visit for more information.