Clean Air Day Clean Air Day 2017 (which we coordinated alongside 100 supporters) was a smash hit, trending at No.1 on UK Twitter for 5 hours. Our air quality messages had a potential reach of 86 million! Clean Air Day 2018 will be happening on 21st June 2018. To find out more about the success of Clean Air Day 2017, download the Celebration Report or visit the website at cleanairday.org.uk and sign up for updates for next June! Please contact [email protected] with any queries.