Any of the following masks which come with a combination filter would be suitable for environments where pollution is high and full of exhaust gases and various particulates including PM10, PM2.5 and respirables (sub-micron). Techno Mask Cinqro Mask Ultralight Combo Allergy Combo Skin plus Techno upgrade kit A combination filter has both a Hepa-type filter layer and a DACC layer. This combination of Hepa-type filter layer and DACC in one single filter provides submicron (smaller than PM 2.5) dust filtering capability, together with DACC capability for filtering gases (VOC’s /Acid gases) and vapours . It is the best type of filter available in our range for dealing with the broad spectrum of pollutants commonly found in major cities across the globe. Typically particulate pollution in cities appears to be in the 2.5 micron size range, above and below. Particles smaller than this are known as respirable dusts, which can lodge deep within the lungs and air sacs. This is the more dangerous type of particle pollution as chemicals from vehicle exhaust gases combustion known to be toxic, are carried by means of the respirable particles. Hence the need for a Hepa-type submicron particle filter together with a DACC Activated charcoal layer. The usable lifespan of the filter is based on the characteristics of the active urban cyclist. If you are using the mask for another activity it still applies, but your breathing rate and activity would put the lifespan of the filter at a proportionally shorter or longer time. If your breathing rate is say half that of a cyclist then the effectiveness of the filter would be twice as long. For cycle commuting on a daily basis we recommend that the filter should be replaced every month or every 69 hours, whichever is sooner. With respect to shipping, we now offer free shipping anywhere on the planet. We do offer a quicker courier service but this is chargeable and can be viewed and paid for at the checkout if required.