Smoke Season Is an HVAC Problem Now, Whether We Like It or Not

When I started in this trade in the eighties, nobody in an Oregon heating shop talked about air filtration as a health matter. You changed a one-inch fiberglass filter to protect the blower motor. That was the reason. Protecting the equipment.

Now we get three or four smoke weeks a summer, and half my August phone calls are people asking what they can do about the haze in their living room. So the trade changed, and here's where it actually stands.

A standard one-inch filter does essentially nothing for wildfire smoke. Smoke particulate is fine — PM2.5, well below what that filter catches. Upgrading to a MERV 13 media filter in a properly sized filter cabinet does a great deal, and it is the single best dollar-for-dollar improvement most valley homes can make. But — and this matters — you cannot just jam a high-MERV filter into a system designed for low resistance. You'll starve the blower, drop your airflow, and in a worst case freeze the coil or overheat the exchanger. The filter has to match the system, which usually means a proper four- or five-inch cabinet.

Beyond filtration, the honest limits: your HVAC system can only clean the air that passes through it. If the house leaks, and most houses here leak, smoke comes in around the doors and the attic hatch and the outlet on the north wall regardless of what your furnace is doing. Sealing is a bigger lever than filtration in a leaky house. We'll tell you that even though sealing isn't the thing we're selling.

One more thing, said plainly: the units advertised as ionizers and ozone generators are not something I'll put in your house. The research on byproducts is not good, and I'm not going to install something in a child's bedroom that I wouldn't install in my granddaughter's. There are contractors in this region who sell them at a very healthy margin. I'd rather sell you a filter cabinet and sleep well.

During smoke events: run the fan continuously on low, keep the fresh-air intake damper closed if you have one, and check the filter twice as often as you think you need to. They load up fast in August.