E&T reporter Tereza Pultarova takes part in a King's College London experiment to find out what Londoners inhale. Each of the study's eight volunteers uses a different mode of transport to get to and from their offices in the city. The detectors are measuring black carbon - a type of particulate matter which generally comes from diesel exhaust. It's mostly related to exposure to traffic, but can also be found underground as it can come from brake wear. The participants are also wearing a GPS watch, which will allow exposure tie exactly to the location to picture how exposure on routes differs. The study runs over two weeks, and during the first week the volunteers use their regular routes. After that, Andrew Grieve, King's College air quality analyst, will analyse the data and propose a different, quieter and less polluted route to see how much exposure could be reduced by avoiding the worst air hotspots.