How to Get Rid of That "Old House" Smell

[Alfred Litton]

Just purchased an investment property built in about 1960.  We've just about finished repainting the interior, but there is a persistent (what I call) "old house" smell.  It's not from a former smoker, and it doesn't smell damp.  but the whole house just smells--old--if that makes sense.  Didn't want to have to lay new carpet since some of the carpet is only about 2-3 years old, but other than that and cleaning the a/c system, what else can anyone suggest that I do.  It's a pier and beam foundation, and they've left the vents covered around the base of the home, so I know I should air it out down there by removing those as well.  My questions are:  1.) what causes this distinct "old" smell? and 2.) what are ways to mitigate it?  Any advice would be appreciated. Thanks!