For digital SLR cameras with removable lenses, dust and debris are a big problem.
This problem, which had long been neglected, was solved through OLYMPUS's unique “Super Sonic Wave Filter (SSWF)” technology.
The traditional system of removing dust opened the shutter (mirror up, valved), which could potentially damage the camera and thus required great care.
In addition to this, allowing fresh air into the mirror box area when lenses were removed, had the potential of introducing more dust into the area, and was hardly the best method that could be taken.