Astral: the machine filter filters particles of 10 micrometers and above. It is a dust filter and has to be changed between patients. Stellar: The machine filter in the Stellar device has a bacterial filtration efficiency of 99.540% on area weight 100g/m². As viruses are typically smaller than bacteria (<0.1 micrometers), the filter is not guaranteed to remove them from the entrained air. The filter has to be changed between patients. Lumis: The standard air filter in Lumis devices is made of non-woven polyester. The average efficiency is >75% for >7 micrometers dust. The hypoallergenic filter is made of acrylic and polypropylene fibres, in a polypropylene carrier. Its efficiency is >98% for >7-8 micrometers dust; >80% for >0.5 micrometers dust. Both types of filter have to be changed between patients.