am using a new resmed S7 and am astonished at the small size of the air intake and filter, the filter is only about 1 cubic inch and would block up with dust quickly, the resmed S6 also has a small filter, all older CPAPs Ive seen have much bigger air intake filters

it is said that the best place for a CPAP is on the floor, but theres usually more dust down there perhaps some CPAPs are intended to be used on a bedside table or shelf??
if so then the machine needs to be secured as its common to tug on the airhose when asleep, pulling the CPAP off any shelf or table

I'm new to all this, but when I got my CPAP, my respriatory therapist told me to put it on my bedside table (I use the Puritan Bennet 420G).  I haven't had a problem with it moving at all, and I'm a pretty active sleeper -- my tubing is routed up and over my head under my pillow, and is plenty long. If you're worried about pulling it off the table, try putting a piece of rubberized shelf liner underneath -- that would probably keep it pretty stationary.