Put two caps full of vanilla extract (you can use other oils, such as lemon and lavender) in a coffee cup (or oven proof dish), then place it in the oven at 300 degrees for one hour. The smell will start to spread after around twenty minutes and encompass the whole house after the hour duration.
Should last for at least a day.
Although not a permanent solution, if you need to remove a bad smell or just want a nice one in your home, this sounds like a pretty simple solution.
