I personally wouldn't because the plastic isn't made for the volatility of essential oils - I imagine it would eventually break down the plastic, rubber and the motor. If you don't have the space for a burner have your tried those ceramic rings that sit on top of a standard light bulb? Or you could make a room spray (just use a PET plastic bottle so your bottle doesn't disintegrate) with oils and distilled water.
============================ Healthy Feet can hear the very heart of Mother Earth. - Sitting Bull
I put a few drops of lavender in my fountain every so often. I have no clue if it has affected the pump or plastic, but it makes sense that it could. They have cute little plug in warmers that look like a large golf ball and you just put a couple drops of oil on a cotton pad. They also seem to work fine for the scent. Most of what I have read about keeping the integrity of the oils says to keep it away from heat, so I stopped using it. It did make my room smell great though!
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