Snap this air filter whistle alarm onto your furnace's or air conditioner's air filters to hear a whistle when the filter is dirty and needs changing.
When your filters are dirty the hole in the whistle is the only part that doesn't get plugged and consequently the only place where there is free air flow resulting in a whistle. Cleaning your air conditioning and heating filters regularly saves energy and money. Product comes in two pieces that snap together through your standard fiberglass or paper furnace filter. You may need to cut a starter hole. Be sure to remove the filter whistle when you change your filters so that you can use it again and again.
Manufacturers put filters in their furnaces to remove airborne particles that might damage the fan and the heating coil. When this "dust" builds up, it can also decrease the efficiency of your furnace, as the furnace has to work harder to pull air through the intake. And that costs you money. Change your furnace filters often.