xenon behavior

[LEIDHOLDT.EDWIN@FORUM.VA.GOV]

I have a question regarding the behaviour of xenon gas in a room,
specifically Xe-133, which is used for lung ventilation studies in nuclear
medicine.  Some people claim that it "sinks" in a room so that the xenon
concentration is higher toward the floor; other people say that it remains
at approximately a uniform concentration throughout the room.  This is an
issue regarding the placement of exhaust ducts in a room.  Does anyone
know whether the xenon concentration is markedly higher toward the floor?
I will be grateful for any help with this issue.
Ed Leidholdt
US Department of Veterans Affairs
San Francisco
Leidholdt.Edwin@FORUM.VA.GOV
415-744-6243