When you buy a commercial carpet freshener, also buy a big box of baking soda. Mix the two half and half and spread over carpets. Then vacuum. The carpet will smell better and you can save money too.
When I took my vacume into be serviced (i am good friends with the folks who own the shop who service my vacume and sewing machince) He told me not to use the carpet powders due to the fact that they get into the moters and bog them down. The filters in vacums are not designs to catch the large amount of fine the dust that those products produce. so what I use to replace it is frabreeze before vacumeing. I find that it works much better, it does nt creat as much dust and it leave the house cleaner.