There's no doubt that a clean smelling room has a very positive effect on the cuctomers reaction when cleaning carpets and upholstery. Over the years I've tried various methods of getting a "clean" smell, but the best one, in my opinion, is to add a dash of deodouriser to the rinse tank. As I mostly use microsplitters the tank only has clear water in it and I don't feel that I'm adding that many chemicals to the clean.