Use worse case scenario on the basis that the full contents of the largest dewar are released into the room over a short period of time.

  • The formula is : % O2 = 100 x Vo divided by Vr
  • Vo = 0.2095 (Vr - Vg)
  • Vr = Volume of room in cu meters
  • Vg = max vol of Nitrogen/Helium that could be released accidentally X the gas expansion value in cubic metres

If calculations show that Oxygen concentration is likely to fall below 19.5%:

  1. Immediate evacuation must take place in event of such a spillage.
  2. Contact the Safety Office to discuss whether oxygen monitoring is warranted.

Calculation

Room Vol [m3]
 
Vol of Liquid [litres]
 
Vg [m3]

Vr-Vg [m3]
Vo [m3]
 

 

Result

% Oxygen

This is below the minimum level recommended by BCGA of 19.5% and constitutes a dangerous atmosphere. Protective measures are required – contact the Safety Office for further advice on requirements.