The smoke-season guide
Smoke season, from the filter outward.
This is what we tell customers before August. It leans on the EPA's published guidance, and we say where we are giving our own judgment.
What smoke is, as far as a filter cares
Wildfire smoke is a mix of very fine particles and gases. A filter in your furnace or heat pump traps particles. It does not remove gases or the smell, and it can only clean the air that passes through it.
Why we start with the system you have
Your furnace or heat pump already moves the air in your house. Giving it the highest-rated filter it can take, with no gaps around it, is the cheapest big step. The EPA suggests MERV 13, or the highest rating your system supports.
Some systems can't take it. A dense filter in a thin slot can starve the blower, which makes the system work harder and can leave rooms short of air. That is why we measure before we recommend.
What we won't sell you
We don't install or recommend ozone generators. The EPA says they aren't safe to use in occupied spaces, whatever the box says.
Before, during and after
What to do in each part of the season.
- 01Spring and early summer
Step 1: Before the haze
Do this while the sky is still clear.
Have the blower, cabinet and returns checked
Get the filter size and rating written down
Close gaps at the cabinet door
Buy two or three spare filters
- 02When the air quality index is poor
Step 2: On smoke days
Keep the house as closed as you can keep it comfortable.
Windows and doors shut
Thermostat fan on
Fresh-air damper closed
One room set up with a portable cleaner
- 03After a smoke spell
Step 3: When it clears
Air the house on the first clean day.
Open windows for a few hours
Look at the filter and change it if it's gray
Wipe the dust that settled indoors
- 04Before the first cold week
Step 4: In the fall
Reset the system for heating.
New filter at the rating the blower can handle
Furnace check
Test the carbon monoxide alarms
What not to buy
Five things that look like protection and aren't.
Ozone generators
Sold as air cleaners, they work by making ozone. The EPA says to keep them out of occupied spaces, and ozone doesn't clear smoke particles.
A filter rated higher than your blower can pull
More restriction means less air through the house. We'd rather give you the right MERV 11 than a wrong MERV 16.
UV lamps in the duct
The EPA hasn't found UV lights in ducts to be a proven answer. They don't remove smoke particles.
Duct cleaning as smoke protection
The EPA doesn't recommend routine duct cleaning, and hasn't found a proven health benefit in most homes.
Any cleaner that won't say what it gives off
If the maker can't tell you the ozone output, leave it on the shelf.
The sealed-home checklist
Before the first smoky day.
Print this, tape it inside a cabinet, and go down it once in July.
Check each one
The filter is the size and rating we wrote down
The filter door closes flat, with no gap
The thermostat fan is set to On
You know where the fresh-air damper is and how to close it
Bathroom and kitchen fans are off unless you need them
One room has a portable cleaner that makes no ozone
Spare filters are on the shelf
Carbon monoxide alarms have fresh batteries
Smoke and the system
What people ask us in August
Does a MERV 13 filter make smoke go away?
It traps more of the fine particles than a basic filter does. It doesn't remove gases or odors, and it only treats air that passes through the system.
Should I buy an ozone generator?
No. The EPA says ozone generators sold as air cleaners aren't safe to run where people are.
Can I run the AC with the windows shut instead?
Yes, if your system cools. Set the fan to On and keep the filter clean. A heat pump can help in rooms the old system never reached.
My carbon monoxide alarm is going off. What now?
Get everyone outside into fresh air and call 911 before you call us. Don't go back in until the fire department says so.
How often should I change the filter in smoke season?
Follow the filter maker. After a smoky spell, look at it: a gray filter has done its work. Keep spares so you aren't waiting on a store.
Start with the filter slot.
Tell us your system and the size in the slot now. We'll say what a better filter can and can't do before we come out.