If the furnace turns on while there is not filter in it, then it can suck up potentially-damaging loose debris. Refer to the owner’s manual for your furnace for any specific instructions regarding how to replace the filter.

If your door is the type that slides off, then you can typically remove it by simply lifting it up until it comes free, and then set it aside.

Look for the vents where the air enters into the furnace system to locate the filter near either the air return duct or the entrance to the blower chamber.

If there is any resistance when you try to slide the filter out, then there may be a locking mechanism keeping it in place. Check for such a system and slide the lock out of the way to release the filter.

Disposable filters have a cardboard frame. If your filter has a plastic or metal frame, then it is a reusable filter than you can clean instead of replacing it with a whole new filter.

If your filter does not have the dimensions printed on it, then measure it with a measuring tape, or check the owner’s manual for the manufacturer’s recommendations to ensure you get the right replacement filter.

The cheapest disposable furnace filters are fiberglass with cardboard frames. This kind of filter will trap large particles of dust and is designed to be replaced every 1-2 months. If you want to upgrade your filter, you can get a slightly more expensive disposable pleated filter, which will trap smaller particles of dust , pollen, and dirt. These filters last longer; from 4 months to 1 year.

Home furnace filters are made to filter air in a single direction so that they do not collapse or fall apart as they trap dust and other debris.

If you put the filter in backwards, then your furnace won’t have sufficient airflow and it can overheat and shut down. This can also happen with a dirty filter, so make sure to keep checking your filter monthly and replacing it when it is dirty.

Remember that if you have furry pets or you run the furnace very regularly, then you will need to replace the filter more frequently. Check your filter every month and any time you notice dust building up in your home.

You might want to make a note of the date you changed the filter to remind yourself to check it again in a month.