The electric car manufacturer Tesla reported results from a chamber test of its new ‘Bioweapon Defense Mode’ filtration system designed to provide ultra-clean in-car air. The car (and operator) were placed in a chamber loaded with PM2.5 at a very high concentration of 1,000 µg m-3, with measurements made in-car and outside. After operating the filtration system, in-car concentrations dropped within a few minutes to levels (supposedly) below the limit of detection of the instrument used. The concentration within the (relatively small) chamber also gradually decreased due to in-car filtration.
However, there is considerable doubt as to whether the level of protection against viruses, with sizes much less than 1 micron, would be similar, notwithstanding the fact that the driver also needs to know in advance of a biological threat. Some commentators suggest the main motivation (albeit a laudable one) is the reduction in in-car PM concentration for health reasons, with the company marketing the vehicles heavily in polluted cities in China.