The sports filter has sub micron filtration capability what this means is that it is able to trap particles less than one micron in size which is more than capable of the removal of 25 micron particulate material pm typically particulate pollution in the cities appears to be in the 25 micron size range particles smaller than this are known as respirable dusts which can lodge deep within the lungs this is the more dangerous type of particle pollution as chemicals from vehicle exhaust gas