An air filtration system

A method of installing an air filtration system and an air filtration system wherein the air filtration system comprises a barrier (3A) configured to be installed at the side of a road and includes a duct (7) and at least one inlet (9,10). The system also includes a filter, such as an activated carbon adsorbent (12,13), an air flow generator (11) such as a fan and an outlet (8). The duct is configured for fluidly communicating the inlet with the outlet such that, in use, the air flow generator is operable to draw air from the road into the inlet and through the filter to be expelled from the outlet. The air filtration system can comprise a kit of parts. The barrier may be a pedestrian or motorway crash barrier and can include a bicycle rack, a moisture sensor and a pollution sensor and/or a screen configured to display pollution information. A network of air filtration systems may be provided wherein each air filtration system may transfer information indicative of pollution levels detected ...