Why Model Y produced in China are equipped with HEPA filter and therefore Bioweapon Defense mode, while those produced in the United States lack this function? It is the same question that American Tesla customers have asked the company, demanding explanations. Tesla initially justified itself by saying that on the platform used for the Model 3 and Model Y there was not enough space to insert the HEPA filter, which apparently is quite bulky, unless you use most of the "frunk", the trunk front. However, this justification collapsed as soon as Tesla started putting the HEPA filter on the Model Y's made in China, and American customers immediately began to make themselves heard.
Fortunately, Tesla did not beg too much, and has updated the production process of the American Model Y by inserting this feature: we know it thanks to the images published on the Twitter page "The Kilowatts", which show us the screen with the symbol of the Bioweapon Defense Mode active on a Model Y Long Range Dual Motor built in July 2021 in the Freemont factory.
On the Chinese Model Y the HEPA filter is installed right behind the frunk, a position that makes it very easy to replace when it comes time to do so, while for example on the Model X it is necessary to disassemble some parts of the car in order to get to the filter; unfortunately we have no photos showing the positioning of the HEPA filter on the American Model Y, but it is very likely that it is positioned in the same way as seen on the Chinese version.