If you have essential oils and bicarb soda on hand, you can save a bundle on room fresheners by mixing the two ingredients in a small container. The bicarb absorbs unwanted odours while the essential oils fill the air with desirable scents.
Handmade craft shop weblog The Burlap Bag says that you should fill one-quarter of a small container with the bicarb soda and add in around eight drops of an essential oil to create a room air freshener. If you're concerned about spills, cover it with aluminium foil and poke holes through it. The freshener will last several weeks in an average-sized room.
The creators use the recipe to control odour from their two cats. The two things I like about this is that you can easily customise the scent, and when the mixture no longer deodorises properly, you can still sprinkle it on your carpet and use it one last time as a carpet deodoriser.
DIY Room Air Freshener [The Burlap Bag]