Denver Real-Time AQI Tracker
Get Alerts For Unhealthy AQI In Your Area
When air quality in your area reaches unhealthy levels, we'll send you a quick alert, along with expert tips on how to reduce your exposure.
What's Actually In Denver Air Today?
What High AQI Means for Your Lungs in Denver
How to Read AQI
The Air Quality Index (AQI) measures how polluted the air is and how it may affect your health.
0–50 (Good): Air quality is satisfactory.
51–100 (Moderate): Acceptable, but some pollutants may pose minor concerns.
101–150 (Unhealthy for Sensitive Groups)
151–200 (Unhealthy)
201–300 (Very Unhealthy)
301+ (Hazardous)
Moderate
Still okay for most, but if you have asthma or allergies, take it easy and avoid long outdoor workouts.
Shop MERV 11 filters→What's the Right Filter for Your AQI Level?
Check Today's Live Real Time Air Quality Index AQI Map in Denver, CO Now
Denver Air Quality Right Now
Tomorrow's Denver AQI forecast: {FORECAST_AQI} ({FORECAST_CAT}), per the Colorado Department of Public Health and Environment (CDPHE).
TL;DR
Filterbuy's live Denver AQI map sits at the top of this page and refreshes hourly with EPA monitor data. When the AQI reaches 100, Filterbuy's action line, put a MERV 13 filter in your HVAC, set the fan to On, run a portable HEPA air cleaner in each occupied room, and close the house up. At higher levels, check AirNow and local guidance first.
Key Takeaways
Ozone is Denver's biggest air problem. The American Lung Association's 2026 "State of the Air" report ranks the Denver-Aurora-Greeley area 8th worst in the U.S. for ozone, based on 2022–2024 data.
Air filters capture particles. Ozone is a gas, so a filter upgrade pays off most on smoke and inversion days.
Smoke wears out filters quickly. Customers tell Filterbuy their filters load up far faster than normal during August smoke.
Fit matters as much as rating. The mistake Filterbuy sees most often is the wrong size, since air that slips around the frame never gets filtered.
How to Read Today's Denver AQI Map
Each dot is an EPA monitoring station showing its current AQI. On summer ozone days, CDPHE often forecasts the highest levels in the southern and western suburbs and the foothills, so watch the station closest to you. For smoke plumes and active fires, switch to Filterbuy's Denver wildfire smoke map.
Why the Live AQI Can Lag Behind the Air You're Breathing
The live AQI is a NowCast, which blends recent hours of readings rather than capturing this exact minute. Filterbuy ran EPA's published formula against a modeled smoke event, and NowCast read 42 AQI points low as the smoke arrived and 79 points high as it cleared. So if you can see or smell smoke, trust your senses first, and reopen windows when the hourly trend falls rather than waiting for the tile to turn green. Learn more about how NowCast AQI works.
What Does Today's Denver AQI Mean for Your Family?
Today's AQI category tells you how much to limit time outdoors and what to change at home. The activity guidance is EPA AirNow's; the at-home steps are Filterbuy's.
Why Is Denver's Air Quality Bad Today?
Denver's AQI follows the seasons, since a different pollutant dominates each time of year, and the Front Range's terrain traps pollution on calm days.
Summer ozone (May–September): Ground-level ozone, or smog, forms when emissions react in strong sunlight and usually peaks in late afternoon.
Wildfire smoke (June–October): Smoke from Western fires can raise fine-particle (PM2.5) readings within hours, pushing Denver's AQI into red or purple.
Winter inversions (November–February): Cold, still air holds exhaust and wood smoke near the ground, creating the familiar "brown cloud."
Spring dust and pollen (March–May): Dry winds carry in dust while trees and grasses release pollen.
Filterbuy's customer service team notices these shifts early: when an inversion or smoke plume settles over the Front Range, calls from families with dustier homes start to climb.
Filterbuy's Pollutant-First Rule: What Actually Helps on Each Bad-Air Day
The main pollutant tells you what your filter can and can't do. MERV ratings measure how well a filter captures particles (EPA), and ozone is a gas. At 100 or above, follow the four action steps below whatever the pollutant.
When a Denver customer calls us with a bad-air concern, our first question is which pollutant is driving it. Smoke and inversion days are filter days. Ozone days are timing days, because no pleated filter catches a gas.
Michelle Wan, Brand Manager and Air Quality Writer, Filterbuy
What Is an Ozone Action Day Alert in Denver?
An Ozone Action Day Alert is a Front Range warning from CDPHE and the Regional Air Quality Council (RAQC) that ozone may reach "Unhealthy for Sensitive Groups" (CDPHE). Active alerts appear in the live box above.
Which Air Filter Matches Today's Denver AQI?
For wildfire smoke, or any AQI of 100 or higher, use a MERV 13 filter. For everyday Denver air, MERV 8 covers most homes. A MERV rating (Minimum Efficiency Reporting Value) shows how well a filter captures particles.
MERV 13 is the tier Filterbuy recommends for smoke. Most furnaces and HVAC systems can use MERV 13 without equipment problems as long as the filter is replaced often (EPA). Shop MERV 8 air filters, MERV 11 air filters, or MERV 13 air filters in your size.
What to Do When Denver's AQI Reaches 100
At an AQI of 100, Filterbuy's action line, put a MERV 13 filter in your HVAC, set the thermostat fan to On, run a portable HEPA air cleaner in each occupied room, and close the house up. First, check AirNow and CDPHE advisories for official guidance.
Put a MERV 13 filter in your HVAC. EPA recommends MERV 13 or higher in central systems during smoke (EPA). This is the whole-home layer, since the central system moves far more air than a portable unit.
Set the thermostat fan to On. On Auto, the system filters only while it's heating or cooling.
Run a portable HEPA air cleaner in each occupied room, bedrooms first. Choose one whose smoke CADR is at least two-thirds of the room's square footage, so a 300-square-foot bedroom needs roughly 200 (EPA sizing chart). EPA advises against any air cleaner that produces ozone.
Close the house up. Keep windows and doors shut, and skip candles, frying, smoking, and vacuuming while smoke is in. Even then, indoor PM2.5 typically runs 55% to 60% of outdoor levels during smoke (EPA).
No central HVAC? In apartments and homes without ductwork, portable HEPA air cleaners are your main layer.
Above 150, keep every step in place, check the filter more often, and keep spares on hand. Replace it when it looks dark brown or black, which can be well before its normal interval (EPA). At 201 and above, follow AirNow and local guidance first and spend time in a clean room. Filtration is one layer of your plan. At 301 and above, follow local authorities' instructions, including any advice to relocate.
The customers who weather the smoke season in the best shape upgrade their filters to MERV 13 before fire season instead of after the smell hits the kitchen.
The Filterbuy Team
For a full checklist, see how to keep wildfire smoke out of your house.
Supporting Statistics: What the Research Shows
1. Denver's Ozone Problem Is Officially "Severe"
In 2022, the EPA reclassified the Denver Metro/North Front Range from "serious" to "severe" nonattainment under the 2008 federal ozone standard. The region has until July 20, 2027, to comply.
Why it matters: High-ozone afternoons are routine in Denver summers.
Source: CDPHE, Federal Ozone Standards and Nonattainment Areas
2. 8.6% of U.S. Adults Currently Have Asthma
The CDC reports that 8.6% of U.S. adults and 6.5% of children currently have asthma (2024).
Why it matters: People with asthma are among EPA's sensitive groups and should follow their doctor's advice. Filterbuy's action line at 100 helps households start early.
Source: CDC FastStats: Asthma
3. Home HVAC Systems Usually Run Less Than 25% of the Time
The EPA notes that HVAC filters clean air only while the system runs, usually less than 25% of the time in heating and cooling seasons.
Why it matters: Filterbuy tells customers to set the fan to On during smoke.
Source: U.S. EPA, Guide to Air Cleaners in the Home
Frequently Asked Questions
What Is the Air Quality in Denver Right Now?
Denver's air quality index is {AQI} ({CATEGORY}) as of {TIME} MT, based on EPA AirNow monitors and updated hourly above.
Is It Safe to Exercise Outside in Denver Today?
Check today's category against AirNow's activity guidance. EPA advises sensitive groups to reduce long or heavy outdoor exertion at Unhealthy for Sensitive Groups, and everyone to reduce it at Unhealthy. If you have asthma, COPD, or a heart condition, follow your doctor's advice.
How Often Should I Change My Air Filter During Denver Smoke Season?
Inspect it during every smoke event and replace it when it looks dark brown or black, which can be well before its normal interval (EPA). Keep spares on hand; an air filter subscription keeps them coming. See how often to change your HVAC filter for normal-season timing.
Can My HVAC System Use a MERV 13 Filter?
Most can. EPA notes that most furnaces and HVAC systems accommodate MERV 13 without equipment problems as long as the filter is replaced often (EPA).
Glossary
Air Quality Index (AQI): The EPA's 0–500 scale for reporting daily air pollution. Higher numbers mean worse air.
CDPHE: Colorado's public health and environment department, which forecasts Front Range air quality.
Ground-level ozone (O3): A lung-irritating gas, commonly called smog, that forms when emissions react with sunlight.
PM2.5: Fine particles 2.5 microns or smaller and the main pollutant in wildfire smoke.
MERV rating: Minimum Efficiency Reporting Value, the ASHRAE 52.2 scale (1–16) for particle capture.
More Denver and Colorado Air Quality Maps
Get Your Denver Home Ready Before Smoke Season
Fire season runs May through October in much of the West, so the best time to get a MERV 13 filter in is before smoke arrives. Filterbuy builds every filter to order in its US plants and ships within 24 hours, in more than 600 sizes. Find your MERV 13 filter size and keep a spare, or set up an air filter subscription.