According to enquiries, a PA filter is included as standard with the Blueair Classic 405 PA and this filters pollen, dust, mould and viruses. The Blueair Classic 405 SM comes with an SM filter as standard. This has the same function as the PA filter and additionally removes unpleasant odours and gases from the air. Currently, we do not have any of the matching replacement filters in our range and we have no information on whether or when they will be available again.