Massive force carriers

A specialized case of air pollutant modeling pertains to the transport and dispersion of very dense vapors that sink to the ground surface and are driven in large part by gravity forces. Such situations are uncommon, but may have catastrophic effects when they do occur examples include release of very cold natural gas from liquified natural gas (LNG) carriers, massive venting of toxic vapors from chemical plants, or release of cold ammonia gas. 

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