The 5 levels of furnace filters from worst to best…
1 – Disposable fiberglass filters. The cheapest are the least effective – shocker! These are designed to protect your furnace, and that’s about it. These are the $1 jobs available in all hardware stores and now even in some supermarkets. You may laugh, but these are better than nothing.
2 – Washable ‘electrostatic’ filters. These have a static charge that attracts dust and other matter. Slightly more effective than fiberglass filters, they still only get 15 to 20 percent of airborne yuck.
3 – Pleated ‘allergy’ filters. The pleats increase the surface area which helps catch most large allergens like pollen and mold. Most catch 35-50 percent of yuck.
4 – Electronic air cleaners. These use electrodes to create an ionized electrical field that, to make a long story full of scientific words short, trap up to 94% of smaller particles and even up to 80 percent of airborne viruses. This is the best you are going to do for your house.
5 – HEPA furnace filters. HEPA stands for High Efficiency Particulate Air filter. These are the mac-daddies and not only block air particles, but also air flow and that’s why they really aren’t recommended for residential use. Hospitals, research facilities, and some manufacturing plants where clean air is vital is where you find the HEPA’s.