The SkyVac 30, 78 & 85 have a very durable wet/dry HEPA filter located under the head. These are easily removed by the twist of a knob.
Both systems use the same filter. They are very durable and last quite a long time if properly cleaned after each days use.
Definition of HEPA from Wikipedia:
High-efficiency particulate arrestance (HEPA), also sometimes called high-efficiency particulate arresting or high-efficiency particulate air, is a type of air filter. Filters meeting the HEPA standard have many applications, including use in medical facilities, automobiles, aircraft and homes. The filter must satisfy certain standards of efficiency such as those set by the United States Department of Energy (DOE). To qualify as HEPA by US government standards, an air filter must remove (from the air that passes through) 99.97% of particles that have a size of 0.3 µm.