An air filter whistle lets you know when it is time to change the filter in your furnace or central air conditioner. This two-part plastic whistle device is snapped onto the filter. When the filter is clean air passes freely through the filter material. As dust and dirt accumulate, more air is forced through the air filter whistle, eventually resulting in a steady, audible whistle to remind you that the filter needs to be changed.
When you hear the whistle, remove the dirty filter, detach the air filter whistle, re-attach the air filter whistle to your new filter, and install the new filter. By changing your air conditioner or furnace filter regularly, you can improve the efficiency of your heating or cooling system, and potentially extend the life of the air conditioner or heating system.