Louisville Air Watch FAQs

Q: What is this?

A: Louisville Air Watch provides real-time air quality data from EPA-approved air monitors located throughout Kentuckiana. The monitors are operated by the Louisville Metro Air Pollution Control District and the Kentucky Department for Environmental Protection. Eventually, it will also show data from monitors in southern Indiana operated by the Indiana Department of Environmental Management.

Q: What do the monitors tell us?

A: The monitors provide data on air pollution levels throughout the area. Air pollutants measured include ozone, particulate matter, sulfur dioxide, carbon monoxide, and oxides of nitrogen.

Q: Why those air pollutants?

A: They have been designated by federal Clean Air Act to be harmful to public health and to the environment. The Clean Air Act requires us to track the amount of these pollutants in the air and take action to keep them at a level deemed healthy for breathing. (More info here: louisvilleky.gov/government/air-pollution-control-district/about-air-pollution)

Q: What do the monitors do, exactly?

A: They use sophisticated instruments to “sniff” the air and tell us what is in it. (More info here: louisvilleky.gov/government/air-pollution-control-district/air-pollution-monitoring)

Q: Does it matter where the monitors are located?

A: Yes. The U.S. Environmental Protection Agency sets strict guidelines for the placement and operation of air pollution monitors. The goal is to provide an accurate assessment of the air quality across the community. (More info here: louisvilleky.gov/government/air-pollution-control-district/air-monitoring-sites)

Q: Why do I sometimes not see data from a pollutant that I previously saw?

A: When data are not available due to maintenance being performed on an instrument or any other reason that may cause invalid data, the pollutant is not shown on the web page for that hour.

Q: What is the Air Quality Index?

A: The Air Quality Index (AQI) is an easy way to tell you about air quality without having to know a lot of technical details. The “Metropolitan Air Quality Index” on Louisville Air Watch shows the AQI from the monitor in Kentuckiana that is currently detecting the highest level of air pollution.

Q: How does the AQI work?

A: Air quality standards are tightened from time to time, but 100 on the AQI will always equal the current standard for a pollutant. Let’s take ozone, for example. Ozone is at an unhealthy level for sensitive populations (seniors, young children and people with asthma, COPD, and other breathing ailments) when it reaches 71 parts ozone per 1 billion parts of air averaged over 8 hours. But you don’t need to carry those numbers around in your head. All you need to know is that when the AQI for ozone hits 101 or above, the air is unhealthy for some people to breathe.

A guide to the Air Quality Index

Q: Why is the Metropolitan AQI different from the individual monitoring sites?

A: The Metropolitan AQI is from Airnow.gov, an EPA-operated air quality website that uses data from the entire Kentuckiana monitoring network to estimate local air quality conditions. Although Airnow’s AQI is based on 8-hour (ozone) and 24-hour (PM 2.5) averaging, it weights the most recent hours of data more heavily in an attempt to give the public – especially sensitive populations – a real-time indication of air quality conditions. Click here for more info from Airnow.gov.

Q: What is the air quality forecast?

A: The APCD, in conjunction with air quality professionals from around the region, produces a daily forecast of air pollution levels for ozone and particulate matter (PM 2.5), which are the two air pollutants of most concern in Kentuckiana. Forecasters look at weather trends and wind patterns as well as sophisticated computer models to predict the next day’s AQI. The goal is to let everyone – particularly sensitive populations – know what the air quality is going to be like so they can plan their day accordingly.

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