A release of helium into the magnet room can lead to death by:

Helium is a colorless, odorless, and non-toxic gas that, when released in a concentrated form, can displace oxygen in the environment. This displacement can lead to a reduced concentration of oxygen in the air, creating a risk of asphyxiation for those in the magnet room. As the levels of oxygen decrease, individuals may experience difficulty breathing, cognitive impairment, and potentially lead to unconsciousness and death if the oxygen levels drop significantly.

While helium itself is not flammable and does not support combustion, leading to risks related to fire or explosion, the primary danger when it is released in a large quantity is the risk of asphyxiation due to the insufficient oxygen in the atmosphere. Hypothermia is also a concern when dealing with cryogenic gases, but in the context of a helium release in a magnet room, it is the risk of asphyxiation that poses the most immediate and severe hazard to individuals in that enclosed space.