Indoor air quality in St. Paul, MN
Air purification and whole-home humidifiers that remove pollutants and keep winter humidity at a healthy level.

Guides for homeowners

Furnace Filter MERV Ratings Explained
A MERV rating tells you how well a furnace filter captures particles of different sizes. This guide explains the scale, what the EPA recommends, and how to pick a filter your furnace can handle.
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Ideal Indoor Humidity in a Minnesota Winter
In a Minnesota winter, the right indoor humidity depends on how cold it is outside. This guide explains the ranges to aim for, why your windows tell you when it is too high, and how to adjust your humidifier.
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Whole-Home Air Purification Options Compared
Media filters, UV lights and electronic air cleaners all install on your furnace, but they do different jobs. This guide explains what each one removes, its limits, and why the EPA warns against devices that produce ozone.
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Whole-Home vs. Portable Humidifier: Which to Choose
A portable humidifier adds moisture to one room. A whole-home humidifier works with your furnace to treat the entire house. This guide compares coverage, upkeep, control and cost factors so you can decide.
Read the guide →Common indoor air problems in Minnesota homes
Dry winter air is a familiar problem in Minnesota. Heating cold outdoor air lowers its relative humidity, so indoor air often feels dry all winter. The EPA suggests keeping indoor humidity between 30 and 50 percent, and below 60 percent to limit mold.
Wildfire smoke is a summer problem that your HVAC system can help with. The EPA’s wildfire smoke guidance for indoor air recommends these steps:
- Use a filter rated MERV 13, or the highest rating your system can handle.
- Set the system fan to “On” rather than “Auto” so air keeps passing through the filter.
- Switch any fresh air intake to recirculate while smoke is heavy.
- Make sure the filter fits snugly, and keep spares to change it more often.
- Keep windows and doors closed when local officials advise staying indoors.
- Run a portable air cleaner that does not produce ozone, sized for the room where people spend the most time.
Radon is a problem you cannot fix with a filter. The Minnesota Department of Health reports that more than 40% of Minnesota homes have dangerously high radon levels. MDH puts the state average at 4.2 pCi/L, more than three times the U.S. average.
Yet only about 1% to 2% of Minnesota homes are tested each year. MDH says the heating season is ideal for testing, because furnaces can pull radon up from the soil. Test kits are sold at hardware and home improvement stores, and licensed professionals can also test.
Krinkie’s does not install radon mitigation systems. Test your home for radon and follow MDH guidance on the results.
Carbon monoxide from fuel-burning equipment
The EPA notes that exhaust from furnaces, water heaters and fireplaces can flow back indoors when a flue is blocked, leaking or the wrong size. It recommends a professional inspection of your heating system each heating season. Keep CO alarms on each level, outside each sleeping area.
Purification or humidification
These two services solve different problems. Air purification removes particles such as dust, pollen and smoke. Whole-home humidification adds moisture to dry air, but it does not clean the air.
The EPA says the most effective steps are to remove pollutant sources and ventilate with clean outdoor air. Filtration adds to those steps but does not replace them.
A furnace filter cleans air throughout the house, while a portable air cleaner treats one room. Neither one removes every pollutant. For portable units, the EPA prefers commercial air cleaners with a known clean air delivery rate.
Some homes benefit from both at different times of year. Read more about whole-home air purification and whole-home humidifiers. A humidifier can be checked during your fall furnace tune-up.
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