Using the ‘air-con bomb’

Posted on August 18th, 2017 by Rob Marshall


If you are experiencing unpleasant smells, moments after turning on your air conditioning, you may need to set-off a ‘bomb’. Put simply, these are aerosol cans that are activated within the car, which penetrate and disinfect the parts of the ventilation system through which the air flows. This includes, within the heater unit, the external surface of the air conditioning evaporator and the vents. They neither maintain the sealed part of the air conditioning system nor the pressurised system, including the compressor.

How do they work?

Imagine your car’s air conditioning system as a refrigerator. The pipes positioned at the rear of the fridge shed the warmth taken from the inside and become warm themselves. Within a car, those fridge pipes are replaced by a radiator unit, which sits at the front of the car (called the condenser). You cannot see the coldest part of the system on a car, because it is situated behind the dashboard close to the air ducts but, on a fridge, the ‘evaporator’ unit can be likened to the ice box.

An ice box tends to become covered with frost and so does a car’s evaporator. Ice boxes tend to stay frosty for some time, because the fridge is switched-on permanently. Should you switch the fridge off, the ice box would warm, the ice upon it would melt and turn to water. As a car’s air conditioning system is powered mainly by the engine, which is not running all of the time, the ice build-up on the evaporator melts more often and the resulting water trickles out from beneath the car.

However, because the evaporator cannot be cleaned manually, due to its inaccessible location, microbes form on its damp surface and it is products from this bacteria that can be smelt initially, when the heating and ventilation system is activated for the first time.

Using the ‘bomb’

Air conditioning aerosol ‘bomb’ cleaners cannot be effective, unless the evaporator is dried, first. For this to happen, the heater must be run for around ten minutes, with the air conditioning switched-off. The heater is then set to ‘recirculate’ and the air flow set towards the windscreen, before the aerosol is positioned within a footwell and activated.

As the engine has to be running with nobody inside the car, as the aerosol empties, this operation must be performed on private land and the car must not be left unattended. The aerosol’s contents should pass through and disinfect the air ducts. Replacing the pollen filter afterwards is a prudent move, too.

On my experience, air conditioning ‘bombs’ are effective, if used regularly (approx. once a year on average), and are an inexpensive way of lowering the risk of you, or your fellow passengers, becoming ill from a dirty air conditioning system.