Hi MK,
Ages ago someone on here posted that they used to add Zoflora to the chamber and I did that and then mine broke a short time afterwards. I'm not saying that adding anything inside the chamber broke it (as it was also a very old version and may have just come to the end of it's life and on the day it broke I had it on for a long time, as the hand held, doing the oven) BUT as I wasn't sure, when my new purple one arrived, what I do now is add about 1/2 a cap full neat of Zoflora onto my coral pad direct, the steam then penetrates that and it does a good clean and leaves a pleasant fragrance.
I find that works great for me - I also rarely use it as a hand held now as I don't want it to break again and frankly it cannot clean an oven properly - only elbow grease can!!!!!
Ange