This fact sheet provides information on Phase 4 of the study.
Phase 4 used a new and improved measurement instrument called a Fourier Transform Infrared Spectrometer to measure air quality averaged over one-hour periods.
Previous phases of the study, conducted in 2005–2006, 2007–2008 and 2009–2010, took samples over longer time periods of up to several days.
Please download the document below.