Do not enter! NMR facilities use large amounts of cryogens which can displace oxygen from the air. If the beeping is an oxygen depletion alarm, you will be in immediate danger if you enter the room. Even if you suspect there is a casualty you should leave rescue attempts to those trained and equipped to do so or you risk becoming a casualty yourself. It is always best to get someone familiar with the facility and to raise the alarm if necessary.
Charles Harrison is a safety advisor at a UK university