Knozone Advisory Called for Wednesday Evening Through Thursday Morning Due to High Levels of Particle Pollution, Potential to Reach Levels 'Unhealthy' for Everyone
People in Central Indiana with asthma, COPD, and many other diagnoses should avoid time spent outdoors from 6pm Wednesday, October 28 until 10am Thursday, October 29 due to stagnant conditions
INDIANAPOLIS—The Indianapolis Office of Sustainability is issuing a Knozone Advisory between the hours of 6:00 p.m. Wednesday (October 28) and 10:00 a.m Thursday (October 29). Hourly fine particulate matter (PM2.5) levels are expected to be in the Unhealthy (Red) to Unhealthy for Sensitive Groups (Orange) Air Quality Index range, included below. The expected weather conditions and air quality monitoring data indicate PM2.5 levels may be elevated during this time with hourly concentrations reaching very high levels. Sensitive groups should remain indoors during this period as much as possible. This is the second Knozone Advisory declared in 2026.
A Knozone Advisory is similar to a Knozone Action Day (KAD). The Indianapolis Office of Sustainability issues a Knozone Advisory when the overall daily average PM2.5 concentrations may not warrant a KAD over the course of a 24-hour period, but hourly values may reach levels in the Unhealthy for Sensitive Groups (Orange) Air Quality Index (AQI) range or higher for several hours. This new protocol aims to bring awareness to short-term air quality conditions. For more information, please review this fact sheet from the Indiana Department of Environmental Management (IDEM).
Unhealthy air quality impacts public health and environmental injustice as vulnerable groups including children, older adults, pregnant people, outdoor laborers, and anyone suffering from asthma, COPD, emphysema, heart disease, or other conditions are at greater risk. Nearly 1 in 5 Marion County community members is at greater risk for severe symptoms due to unhealthy air quality.
Community members can sign up for text or email alerts at smogwatch.in.gov to be notified of unhealthy air days early. Knozone.com and the EPA's AirNow website and mobile app are other great resources for monitoring local air. Community members can also follow @SustainIndy on Facebook, X, and Instagram for reminders about Knozone Advisories and Action Days.
To protect residents and local air quality, the Office of Sustainability issues Knozone Advisories and Action Days when levels of certain pollutants rise above acceptable thresholds. During Knozone Advisories and Action Days, the air quality may become unhealthy for sensitive individuals due to increased ground-level ozone and/or fine particles—two of the most common pollutants in the United States.
While the ozone layer high in the atmosphere helps protect us from the sun’s rays, ozone down where we breathe is dangerous for public health. Ground-level ozone is created when a chemical reaction occurs between sunlight and hydrocarbons from emission sources common in urban areas, like gas-powered vehicles and lawn mowers. Fine particulate matter (or PM2.5) refers to microscopic particles in the air, including dust and smoke, that we can inhale into our lungs and cause damage. This can even be caused by wildfires or dust clouds blowing from thousands of miles away.
Every day, and especially on Knozone Advisories and Action Days, residents are encouraged to reduce their contribution to fine particulate matter (PM2.5) through these simple actions:
Never burn trash, furniture, leaves, or grass clippings. Burning these items is always illegal in Marion County and punishable by fines up to $2,500. If you encounter illegal open burning, utilize the RequestIndy mobile app or website or call the Mayor's Action Center at 317-327-4622. If it's an emergency, call 911.
Avoid campfires, bonfires, and barbecues until the air quality returns to healthy levels. The rules and regulations for open burning are available on the Department of Business and Neighborhood Services' website: indy.gov/BNS
On Knozone Advisories and Action Days caused by particulate matter, take precautions to reduce your exposure to outdoor air. This includes:
staying indoors,
keeping windows closed,
running an air conditioner,
running a high-efficiency particulate air (HEPA) purifier, and
if in a vehicle, using the "recirculate air" function (looks like a car with a sideways U-turn arrow) and keeping windows closed.
Additionally, you should refrain from activities that degrade indoor air quality, including burning candles and vacuuming.
If you must be outside, N95 or P100 masks that fit and are worn properly can provide some level of protection from particulate pollution. These masks do not protect against ozone. Cloth face masks or traditional surgical masks do not provide adequate protection from smoke. The EPA recommends "particulate respirators" that have been tested and approved by the National Institute of Occupational Safety and Health (NIOSH). Learn more here.
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