Comment by warrenm

Venting 120l of liquid helium (or about 84,000l of gaseous helium) really isn't that much of a health concern

I've seen multiple vents of ~1500l of liquid helium (~1,050,000l of gaseous) in a single day from a couple bad MRI units when I worked at a company that makes them

Only "dangerous" place to be was in the fragmentation path of the burst disc (which was enclosed in the top of the unit (at the time)), or directly in the path of the nearly-liquid (ie extremely cold) helium as it vented

It dissipates extremely rapidly