Building off the success of the white flag initiative, the Good Neighbour Campaign has been working to continue to provide Hamiltonians with the tools and skills needed to monitor air quality within their neighbourhoods. Recognizing that our next method needed to be simple, easy to interpret, precise, robust, and affordable, we decided to utilize the methodology of George Sorger, a McMaster professor who has studied the relationship of tree lichen to air quality (specifically S02 and N02, good indicators of airborne pollution).