Ventilation and extraction requirements may require low level, routed via ducting or fresh air supplied.

Where liquid nitrogen typically used in cryogenic storage vessels is used low level ventilation is required. liquid nitrogen is a dense gas and will fall to the floor. When liquid nitrogen vaporises to a gas it expands at a ratio approx 700:1, as the nitrogen competes with the space it depletes the oxygen posing a significant asphyxiation hazard.

"The ventilation rate shall be no less than 5 times the expected nitrogen boil-off rate of all the liquid nitrogen freezers combined. " BCGA GN 19.

In this scenario Britannia calculate the ventilation requirements based on the room size and equipment used to provide a solution that is capable of  initially extracting air to prevent nuisance alarms and in the case of an emergency will escalate to extract a large amounts of air and provide multiple room changes.

 

Extraction for Liquid Nitrogen vapour should always be fitted at low level for safety. LN2 vapour is a heavy gas, meaning it is heavier than air, and will therefore will sink to floor level.

If Liquid Nitrogen extraction is fitted at a high level, then the gas will be removed at the level of breathing which is a huge danger to health.