Your furnace filter should be replaced every 90 days to keep your heating and air conditioning system as efficient as possible. A clean filter also traps the irritants found in air a lot easier than an old, dirty one. Proper disposal of the old filter is essential to prevent all the collected debris from becoming airborne once again. Remember that a an old filter has 90 days of trapped material in it, so many irritants, allergens and other particles can easily become airborne.
Turn the power off to the furnace to prevent it from turning on while you are removing the old filter.
Remove the old furnace filter from duct system. Look near the side of the furnace where the return air duct connects to the furnace as this is the most likely location of the furnace filter.
Place the old furnace filter in a plastic bag. Tie or tape the end completely shut to contain the filter and prevent it from releasing the trapped particles.
Carry the plastic bag with the furnace filter immediately to your outside trash can and put it inside. This will ensure it is disposed of in a timely manner.
Put the new filter in the furnace and turn the furnace back on.