A green barrier was installed in a case study school in Sheffield, UK. This dataset shows the air pollution concentration pre and post such GI intervention at the case study school (Sch-GB site) and at two other sites serving as control for data comparison and contrast. The control sites are located within a 2 km radius from Sch-GB, and comprise a site in the city centre (City site) – providing an urban background – and another school playground without a green barrier (Sch-NoGB site).   The dataset show pollution concentrations as monitored by the air quality equipment, and corrected concentrations after data de-seasonalisation.