Gases/vapors heavy, behavior

When chlorine is released into the air from a container, liquefied chlorine expands 470 times to the gaseous phase. It is quickly dispersed and at a faster rate by air motion if a strong wind is blowing. Chlorine is heavier than air and can accumulate in low-lying regions. Under wet conditions it is quickly hydrolyzed, or, in bright sunlight, it is photolyzed to form chlorine radicals. Some heavy vapor dispersion models for chlorine have been developed and found deficient. Some models are deficient because methods used to estimate the dispersion of heavy gas clouds apply to the case of dispersion over flat, uninterrupted terrains. It has always been assumed that the concentration-time profile follows the top-hat behavior. 

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