Air Quality Index is a free, nice and simple application that displays the current value of the AQ index for more than 60 countries (1000 cities) in the world. This software tool (portrait orientation, Android 5 or newer) works on the tablets, phones and smartphones that are connected to the Internet. At first, it gets the local coordinates (latitude and longitude) from your device's GPS and then retrieves the AQ index from an Internet server (aqicn.org). The value of this index represents the air pollution level at your location (given by the closest station in your city). This index is computed every hour and includes the measurements of all known pollutants (PM 2.5, PM10, NO2, CO, SO2, O3); its level means:

0 - 50: (Good) - Air quality is considered satisfactory, and air pollution poses little or no risk.
51 - 100: (Moderate) - Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.
101 - 150: (Unhealthy for Sensitive Groups) - Members of sensitive groups may experience health effects. The general public is not likely to be affected.
151 - 200 (Unhealthy) - Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects.
201 - 300 (Very Unhealthy) - Health warnings of emergency conditions. The entire population is more likely to be affected.
300+ (Hazardous) - Health alert: everyone may experience more serious health effects. Everyone should avoid all outdoor exertion.

Features

-- instant display of the AQ index for your current location
-- AQ index for all major cities in the world
-- no ads, no limitations
-- only one permission is required (Location)
-- this app keeps the phone's screen ON
-- the colour of the windmill follows the AQ index
-- the value of AQ index can be said in English