You can get citronella candles, which in effect, the oil is being vapourised, so yes.
Keep it away from the rabbits, make sure you buy a good quality oil, that's not been filled out with rubbish.
Here's a good one
http://www.naturallythinking.com/products/Citronella-Leaf-Essential-Oil.html
If you buy elsewhere, make sure it is PURE ESSENTIAL OIL as other sellers might make a profit by bulking it out with other ingredients (which I cannot guarantee are safe with buns)
Just a few drops in a "vaporiser", or an "oil burner" with a small amount of water (sometimes they are one and the same thing) near, but not in reach of the buns, should suffice.
You could make up a VERY WEAK solution of one drop citronella to 300ml solution suitable for spraying, to mist the air, however, if any should gain contact with living tissue, it is IMPORTANT to note that citronella multiplies the damage caused to skin by the dangerous sun's rays by an extortionate amount (I cannot remember the exact amount, but I do remember it says to NOT PUT ON FLESH OPEN TO THE SUN'S RAYS) it can basically increase the risk of skin cancers greatly (this would include fair furred or albino rabbits))
You could spray the rabbits enclosure but not get it on them, the only time they could "safely wear it" would be when there is no sun, then there's the risk of ingestion.
A candle or burner would be the safest bet.
(you can make a lotion 1 drop citronella to 100ml lotion, for your own skin, but again only to be used at night)
Hope this helps x