In general, birds do not create a smell. However, sometimes what you feed them can create unpleasant odors. We recommend you change your birds bedding a minimum of weekly if you are using a manufactured bedding (check with us to make sure the bedding you are using is safe). If you are using paper towel or newspaper, it is recommended you change that daily. Uneaten broccoli needs to be removed from the cage ASAP or it can generate a very unpleasant odor. If your bird's poo has an unpleasant odor, I recommend you take him to you veterinarian to have a check up.
We use a small crock pot with filtered water and a couple drops of essential oils to have a calming aroma in the large area of our shop. There are many different blends you can make yourself or purchase. Essential oil is the key. If your product does not say 100% pure essential oil, it may not be safe.
You can find essential oils in many health food stores and natural grocery stores. There are several online venders that sell them as well.
I have never had an issues with this method, but I have no control of what people do in their home. When dealing with birds, I always caution "less is often times better". You do not need to use gallons of essential oil. Use it very sparingly.
Erring on the side of caution, I have the crock pot in a separate room than what the birds are directly in. Please use caution and remember, while this has worked for me there are no 100% guarantees.