Idle-Reduction Technology Offers Multiple Benefits

Those of us who have been around for a while remember the days when a semi-tractor would idle all night long at the truck stop, keeping the cab warm for the driver as he slept. Fuel was cheap, and the diesel engine could idle happily forever. All this changed in 2007 with the introduction of more stringent pollution-control methods, including the diesel particulate filter (DPF). Today, idling is the bane of the fire industry because our apparatus are at idle so much of the time.


Diesel Engine Aftertreatment (DEA) systems consist of DPF and Selective Catalytic Reduction (SCR) technologies. Today, most DEA systems combine DPF and SCR technologies in the same canister.

The DPF canister captures soot and ash particulates in the exhaust stream. The soot burns off naturally when the exhaust is hot enough. If it does not get hot enough (such as during excessive idling), the engine then performs a “regeneration” in which fuel is introduced into the system to increase the temperature of the exhaust artificially. Idling keeps the in-cylinder temperatures low, which leads to more soot in the exhaust and less of the soot being burned off passively. These factors cause more stationary “regeneration” events, which, in turn, burn more fuel and oil and waste operators’ time.

SCR canisters use diesel exhaust fluid (DEF) to break down the nitrous oxides.

Fire Apparatus Manufacturers’ Association (FAMA) member companies developed guidelines to counter the problems caused by DPFs and idling of emergency vehicles. They would also lower costs for fuel and maintaining and repairing the DEA system. The first emergency vehicle idle-reduction technology (IRT) system was launched in 2009. Other comparable systems were subsequently introduced, but the most effective way to combat DPF issues is to simply reduce the need to run the engine.


IRT solutions are available in two versions: electric and internal combustion engines. The electric system uses special-technology batteries, the same batteries used in electric vehicles. In the internal combustion system, a small gas or diesel engine provides power when the main diesel is shut down. In other words, IRT offers customers the option of powering many of their emergency vehicles’ systems with either a small diesel engine or a battery.

How IRT Systems Work

As noted above, one system revolves around a diesel auxiliary power unit (DAPU). The other is centered around battery technology.

The DAPU system monitors the emergency vehicle systems. When the conditions are correct, a small displacement DAPU fires up. Shortly after, the chassis engine automatically turns off. The DAPU engine typically is 1/10th the size of the chassis engine and operates under a significant load while “sipping” fuel from the chassis fuel tank. The transition from main to auxiliary engine can be controlled by the operator or programed to switch automatically. The result is a cleaner, more efficient way to produce the energy needed to maintain the emergency vehicle’s systems such as chassis batteries, air-conditioning, heating, warning lights, air-brake air pressure, and 120/240VAC (volts alternating current). When in idle-reduction mode, the vehicle uses the least amount of diesel fuel possible as efficiently as possible and does not wear out the chassis engine and chassis DEA system.

Some DAPU idle-reduction systems can make 120/240VAC available to customers, even when the truck is not in idle-reduction mode, for powering tools, fans, and high-voltage scene lighting.

The battery-operated system also monitors the emergency vehicle system and works as follows: when conditions are correct, the chassis engine automatically turns off. Power to maintain the chassis system is then maintained by a set of special-technology batteries, which provide power to the vehicle’s electrical system for scene support. If the batteries become depleted, the operator is given a brief warning. Shortly after, the chassis engine automatically restarts. These systems eliminate fuel usage and emissions when operating in battery mode; they also reduce apparatus noise. The special batteries offer power storage density; work in all environments; and do not necessitate new methods of disposal, training, or handling.


Saving money and conserving fuel are the obvious reasons for shutting off the main engine at the scene.

  • A typical urban pumper using idle mitigation cuts engine hours by more than half.
  • Oil change intervals are usually determined based on engine hours. This can translate into fewer oil changes and less time out of service.
  • Extended idle reduction enables a crew to log fewer engine hours for the same emergency response. This means reduced wear and tear on the engine, extended maintenance intervals, and lower service costs.
  • The apparatus spends more time in service. Engine service is expensive and, typically, is not covered under warranty past five years.


Fire and other emergency departments can experience benefits beyond efficiency and cost savings by implementing IRT in their apparatus and other vehicles.

Health. Firefighter and citizen exposures to diesel exhaust are decreased. National Fire Protection Association (NFPA) 1500, Standard on Fire Department Occupational Safety, Health, and Wellness Program, and NFPA 1901, Standard for Automotive Fire Apparatus, recommend that exposure to exhaust be minimized. The longer the vehicle engines run at the scene, the greater the exposure will be.

Noise. Eliminating engine idling reduces on-scene noise. This scene-safety ambient/background noise reduction improves communication, allowing firefighters to operate more cohesively and efficiently. This benefits not only the firefighters but also individuals who might be the subjects of the firefighters’ emergency activity, whether a car accident or other type of emergency call. It also decreases the noise pollution that can potentially contribute to hearing loss.

“Going Green.” Greenhouse gas reduction is another benefit of IRT technology. Less idle time means fewer gases being released into the environment. Shutting off the main vehicle engine instead of letting it idle is a common method of “going green” in vehicle design. A similar approach can be seen in newer light-duty cars and pickups, which are often designed to have the engine shut off when the vehicle is stopped for red lights.

The internal combustion engine IRT allows the main engine to stay off for the entire time on scene when pumping is not required. Electric IRT allows the engine to remain off until the charge in the system drops to a point where the engine needs to recharge.

Public Relations. IRT can contribute significantly to “go-green” goals by offering improvements to sustainability and air quality. Moreover, IRT demonstrates to the public that the fire department is providing safety services that consider the taxpayers’ well-being and wallets.


IRT is virtually transparent to the user and easy to use. As recently as 2017, new developments in electronic control systems advanced the idle reduction experience. FAMA member manufacturers took everything they learned from a worldwide network of service centers, dealers, and customers and delivered the next evolution in emergency vehicle IRT, which is available now and will be for many years to come. This next generation of systems will have the least invasive human-machine interface available. These systems work behind the scenes to serve the customers’ needs. Serviceability of the DAPU was expanded to satisfy all service centers. The available DAPU and battery APU systems work across all chassis platforms. FAMA manufacturers and the entire industry are committed to perfection that drives small improvements, some of which will be introduced later this year.


Additional information on IRT is available from FAMA members. When planning to add or expand IRT in your department’s apparatus/vehicle fleet, consider the following:

  • How diesel engine exhaust from an idling chassis engine affects the health and performance of emergency workers.
  • How a small DAPU atop the vehicle would lower the amount of carbon monoxide emissions the emergency worker inhales while wrapping up a scene.
  • How the cool interior of a chassis cab maintained by IRT helps firefighters to recover from unrelenting hot summer weather.

Fire departments incur significant costs related to the repair and replacement of emissions systems combined with the cost of purchasing “cleaner” diesel fuel at the pump. The days of fire trucks idling while emitting black and white smoke out the tailpipe must come to an end, and engine idling needs to be curbed.


FAMA is committed to the manufacture and sale of safe, efficient emergency response vehicles and equipment. FAMA urges fire departments to evaluate idle-reduction technology in their next apparatus purchase as well as the full range of safety features offered by its member companies.

FAMA Forum creative content is contributed by unpaid volunteer authors. Any opinions expressed herein are exclusively those of the author and are not intended to represent the views of FAMA or its member companies.