There are actually specific reasons why we are unable to completely shut down the fire engines and ambulances every time that they are not in the stations.
The City's fire and emergency medical vehicles carry a wide array of important equipment used to treat patients, fight fires and communicate with each other. Many of these items, especially the medications and sensitive and expensive medical devices we carry, would be subject to damage in certain temperature extremes. In the summer it is necessary to keep these items cool and in the winter it is necessary to keep them warm to ensure that the electronic equipment will operate properly and the medications will not suffer the ill effects of dramatic temperature changes.
In addition to the concerns over weather conditions, a large number of items on the fire engines and ambulances require a constant charge to guarantee optimal and prolonged use. This includes but is not limited to suction units for clearing a patient's airway, thermal imaging cameras for seeing through smoke, portable radios for communication, spare batteries for cutting tools, on-board dispatch computers and flashlights for rescue operations.
In general, a larger diesel engine like those found in emergency vehicles requires more electricity to start than a standard gasoline or diesel engine that is not designed for this purpose. In addition, the electrical drain on a standard diesel operated engine, a dump truck for example, is much less than on a fire engine or ambulance for the reasons noted above. If the engines and ambulances are shut down completely for lengthy periods of time, without an outside power source, there is a slight possibility of them not starting again when needed. We do try to shut them down whenever the amount of time and temperature conditions will allow but these instances are less common than not and occur on a case-by-case basis. Manually shutting down each and every piece of equipment that causes a drain on the system is simply not possible.
When the emergency vehicles are in the station they are always plugged into a power source to keep the equipment and batteries charged, but when the vehicles are out of the station they need to rely on the power generated by allowing the vehicles to idle or run when parked.
It is our duty to the citizens to ensure that we are always operating at optimal levels when responding to emergency calls. There are times, however, when our emergency vehicles are required to be out of the station on training seminars, business pre-plans and inspections, hydrant maintenance and a litany of other "non-emergency" functions. The tools and equipment we use require us to leave the vehicles "idling" or running during these tasks unless it is for a very brief amount of time or certain other conditions are met that will allow for a shut down.