Filterbuy's Four Steps at AQI 100

At AQI 100, start with official guidance from Iowa DNR and Polk County, including any stay-indoors or evacuation orders, and check the AirNow reading. Then:

1. Install a MERV 13 filter. EPA notes that most furnaces and HVAC systems can take MERV 13 without equipment problems when the filter is replaced often.

2. Set the thermostat fan to On. Auto filters only while the system heats or cools; On filters continuously.

3. Run a portable HEPA cleaner in each occupied room, bedrooms first. EPA recommends a CARB-certified unit with a smoke CADR of at least two-thirds of the room's square footage, so a 150-square-foot bedroom needs a CADR of 100 or more. Skip ionizers and ozone generators; EPA advises against cleaners that produce ozone.

4. Close windows and doors, set any fresh-air intake to recirculate, and skip candles, frying, smoking and vacuuming without a sealed unit.

On ozone days, closing up still helps because ozone breaks down indoors; the filter steps target particles.

Why Des Moines AQI Readings Can Look Off or Lag

AirNow's hourly particle readings use NowCast, which weights the most recent hours, while the federal standard is a 24-hour average. When smoke moves in or out quickly, the two can disagree.

Monitors also describe neighborhoods, not streets. Before dawn on May 24, 2023, smoke from driftwood burn piles at Saylorville Lake slid down the Des Moines River valley under an inversion. By 4 a.m., Des Moines station WHO 13 reported, the Polk County Health Department sensor read Very Unhealthy while West Des Moines read far lower.

Is Des Moines Air Safe to Breathe Right Now?

That depends on the reading above and who is breathing it. AirNow says sensitive groups should cut back on long or heavy outdoor exertion once the AQI passes 100, and everyone should above 150. Iowa DNR counts people with heart or lung disease, older adults, children and teenagers, and outdoor workers as sensitive to fine particles. Your doctor's advice comes first.

Going to the Iowa State Fair in August? Check the map that morning, and on an ozone day, walk the grounds before the afternoon peak.

Des Moines Air Quality Alerts and Burn Rules

Iowa DNR issues Air Quality Alerts for smoke or ozone, relayed by the National Weather Service in Des Moines. Polk County sends EnviroFlash email notices from its current AQI page, and Filterbuy's alert sign-up on this page emails you too. The AirNow Fire and Smoke Map and Filterbuy's Des Moines wildfire and smoke map track smoke.

Open burning has been banned in Des Moines, West Des Moines, Clive, Windsor Heights, Urbandale, and Pleasant Hill since September 21, 1983, under Polk County rules. Elsewhere, rules vary by property, but no open burning is allowed at AQI 90 or above.

What's Actually in Des Moines Air

Ozone forms on hot, sunny afternoons from vehicle and industrial emissions, and wildfire smoke adds gases that feed it. Fine particles, or PM2.5, come from Canadian wildfire smoke, spring prairie and habitat burns, and winter haze.

Midwest research finds particulate nitrate now makes up as much as 40 percent of the region's winter fine-particle mass, formed when farm ammonia meets nitrogen oxides from vehicles and power plants. Year-round, the metro still passes the federal particle standard, per the 2026 State of the Air report.

Canadian Wildfire Smoke: Des Moines' Biggest Air Quality Swing

Canadian smoke can turn Des Moines air unhealthy within a day. On May 7, 2016, it pushed the city's daily average PM2.5 to 50.7 micrograms per cubic meter, according to the State Hygienic Laboratory at the University of Iowa. On June 3, 2025, Iowa DNR issued a statewide alert, and on July 31 it expected exceedances across most of Iowa. Our Canadian smoke guide explains how plumes travel.

What If Your Des Moines Home Has No Central HVAC?

Filterbuy makes HVAC filters, so we'll be direct: without ducts there is no filter slot, so portable HEPA cleaners are your primary layer. With radiators, baseboards, a ductless heat pump, or window units, run a CARB-certified HEPA cleaner in each occupied room during smoke. If that is out of reach, EPA describes a do-it-yourself box-fan cleaner built with MERV 13 filters. Use a certified fan made in 2012 or later, never leave it running unattended, and treat it as a stopgap until you can get a certified air cleaner.

Our Take: Des Moines Has Two Kinds of Bad Air Days, and Filters Fix One

Filterbuy has made HVAC filters in the U.S. since 2013. With a D on both pollutants, the first question on a bad day is which one the map names. Ozone peaks in the afternoon and fades after sunset; smoke can arrive at any hour, often with a campfire smell.

We'll say it plainly as a filter company: on an ozone day, no filter we make will help, so exercise in the morning and close up in the afternoon. On a particle day, the four steps apply, and the fan setting matters as much as the filter. Smoke tends to arrive in air-conditioning season, when a fan on Auto sits idle between cycles.