Like most essential oils it is generally fine in small diluted doses but consider the effects of basically steaming the wood while being in an enclosed area with it for a prolonged period of time. I do not have any more information but if you do a little research you will find that high doses of the stuff are not at all healthy.

In my initial comment I was simply siting my own experiences of dealing with a eucalyptus tree and picturing a scenario where I was in an enclosed area with it. The strong undiluted oils definitely acted as a skin irritant for me and breathing the oil was assuredly unpleasant.