: The "nominal" size is a rounded number for marketing; the "actual" size is slightly smaller to ensure a snug fit. 2. Understand MERV Ratings

Different materials offer varying levels of filtration and durability.

: The cheapest option, designed mainly to protect your furnace from large debris. They do very little for indoor air quality. LJ Rolls considers these "basic protection" only.

The Minimum Efficiency Reporting Value (MERV) tells you how well a filter traps particles. MERV Rating Large particles (lint, dust) Protecting the furnace motor only. MERV 5–8 Mold spores, hair, pet dander Standard homes with no pets or allergies. MERV 11–13 Smoke, bacteria, smog Homes with pets, smokers, or allergy sufferers. MERV 14–16 Viruses, fine tobacco smoke Highly sensitive individuals or clinics. 3. Choose Your Filter Material

Your lifestyle dictates the intensity of filtration you need:

A high-end MERV 13 filter that is clogged with dust is worse for your air—and your energy bill—than a clean MERV 8. Experts at Guardian Technologies recommend replacing filters every , or as often as every 30 days during peak heating/cooling seasons or if you have multiple pets.

: MERV 13 is excellent for asthma but should be checked for compatibility with your HVAC system’s airflow requirements. Expert Maintenance Tip