Marcus never thought about the air filter until his daughter started sneezing every morning. The filter behind the hallway vent had not been changed since they moved in. It took him five minutes to fix. Here is everything he needed to know.
1. Find your size
Pull out the old filter and read the frame. You will see three numbers, like 20 x 25 x 1. That is width, height and thickness in inches. Buy the same size. If there is no old filter, measure the slot and round to the nearest standard size.
2. Pick a MERV rating
MERV tells you how small a particle the filter can catch. Higher catches more, but it also slows airflow a little.
- MERV 8 catches dust, lint and pollen. A good choice for most homes.
- MERV 11 also catches pet dander and finer dust. Good for homes with pets or allergies.
- MERV 13 catches even finer particles like smoke. Check your system manual first, because some older systems are not made for very dense filters.
3. Point the arrow the right way
Every filter has an arrow on the frame. It shows which way the air flows. Point it toward the furnace or air handler, away from the room.
4. Set a reminder
- A standard 1 inch filter: about every 90 days.
- With pets or allergies: about every 60 days.
- Thicker 4 inch filters usually last longer. Check the box.
Write the date on the frame with a marker when you put it in. Next time you will know exactly how old it is.
For the rooms that need more
A furnace filter cleans the air that moves through your system. A HEPA air purifier cleans the air in one room, all the time. Many families use both: a good filter for the whole house and a purifier in the bedroom.
Marcus put a reminder on his phone and a small purifier next to his daughter's bed. The morning sneezing stopped within a week.