I am in the process of finishing my basement and need to install a cold air return. I understand that a central location at the floor is better than an exterior wall. My forced air gas furnace is in the central part of my basement and I can easily tie into the existing cold air return on the back wall of the furnace room. This location, however, would open the cold air return right before the air enters back into the furnace. If I open up a cold air return right next to the furnace will all the air be pulled in from that return, or will air still be pulled from all the returns. Also, is it dangerous to put a cold air return off the back wall of the furnace room which also has two water heaters in it.