Furnace filters: what to buy and how often to change it
The filter is the most important part of your indoor air. Most people are using the wrong one or forgetting it.
Between duct cleanings, your furnace filter is what keeps dust, dander and pollen out of the system. Most homes have the wrong filter, the wrong size or a filter that has not been changed in a year.
MERV rating is the measure of how fine a particle the filter catches. The cheap blue fiberglass filters are MERV 2 to 4 and catch almost nothing. MERV 8 catches dust and pollen. MERV 11 to 13 catches pet dander, smoke and fine particulate, which is what you want if anyone has allergies or asthma. Above MERV 13, most residential furnaces cannot pull enough air through the filter and you can damage the blower.
How often
One-inch filters every 60 to 90 days, monthly with pets or during wildfire smoke season. Four-inch media filters every six months to a year. Write the date on the edge of the filter when you install it.
The Seattle wildfire season
August and September smoke events have become routine. A MERV 13 filter, changed after each smoke event, makes a real difference indoors. If the smoke was heavy and the windows were open at all, a duct cleaning afterward removes the layer of ash that settled in the system.
Need it handled?
Negative-air duct cleaning of the whole system, trunk lines included, with the furnace blower and coil cleaned too. Air Duct Cleaning · (206) 434-0779
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