I am using clary sage and lavender to see if it will help bring on labour, I put a few drops of each into a bath last night, and also massaged my belly with them when I got out, and the whole house smells of it, which would be great if they smelt nice but they are quite horrible really and so I have all of the windows open trying to get rid of it, but, if it was a nice smell, it certainly seems a good way of getting the aroma into the air
Other ways are to burn in an oil burner (watch the candles) or put a few drops on a lightbulb and switch the light on for a bit.