Can small fans be mounted in the upper portion of the wall in a nursing home? We are looking to add fans for increased air movement in our hallways. I know we must keep them 18" from the ceiling to comply with fire safety. Is there any other restriction that I am not finding, that would not allow us to be able to do this? The fans would still clear head height even with the 18" drop, and would not pose a risk to someone hitting their head on it. Any information would be appreciated. Thank you.