Xenon and vent placement

[broseus%nihrsb.dnet@dxi.nih.gov (Roger W. Broseus, Ph.D.; RB27m@NIH.GOV)]

On xenon flowing down hill and placement of vents:

"Effective Specific Gravity

"Frequently, the location of exhaust hoods is mistakenly based on
a supposition that the contaminant is 'heavier than air' or
'lighter than air.'  In most health hazard application, this
criterion is of little value.  Hazardous dust, fumes, vapors and
gases are truly air-borne, following air currents and are not
subject to appreciable motion either upward or downward because of
their own density. [after giving an example for
tetrachloroethylene, which has a molecular weight of 164, at a
concentration of 1- ppm, it is noted that:] . . . the effects of
window ventilation, cross currents, traffic and heat can dwarf
into insignificance the effect of specific gravity."

From: Industrial Ventilation; A Manual of Recommended Practice. 
American Conference of Governmental and Industrial Hygienists. 
Lansing, MI.  1978.  pp 1-3 to 1-4.

I hope this helps to clear the air on this topic.

-- Roger W.  Broseus