RE:ShelfYes, struck me as odd too and based on the other thing on the shelf I cannot tell whether it is solid or not. I had to look at Brad's video to confirm my recollection of the intake. It was from the bottom, but I also noted that Brad's unit was white and this one is grey. Don't know if these are slightly different designs and could not bother going back in time to see the demo on the grey unit. Remember that they were supposed to be mounted on walls but that may have been an easy way to say they are easy to mount anywhere...close to an electrical plug. I would like to think that the installers have some kind of guidelines as to best locations in a room and best heights based on some kind of an airflow assessment and where individuals are likely to congregate the most i.e. the closer they are to the unit, all things being equal, detection should be faster, no?