If we were looking to buy a new filter today for our HVAC (heating, ventilation, and air conditioning) system, we’d opt for one rated MERV 13. These filters efficiently capture pollen, mold spores, dust, and even ultrafine particulates, including from wildfire smoke. This helps to keep your indoor air clean and protects your equipment from dust buildup and clogging.A 2024 California regulation requires manufacturers to publicly list their filters’ air resistance — effectively the strain they put on HVAC systems. This is a real step forward because, for the first time, homeowners (and Wirecutter writers) have a way to objectively compare brands. Our MERV 13 picks put so little strain on HVAC systems that we’re confident they’ll be fine to use even with older air-handling equipment. But if you’re concerned, you can always choose a lower-MERV filter (like a MERV 8); they are effective only on larger particles, like pollen, but they offer less air resistance.