Last Revised: June 06, 2022


The potential for release of large quantities of cryogenic liquids in an MRI or NMR Spectroscopy room or a gas storage room may necessitate the installation of a fixed air monitoring system to alert occupants of oxygen deficient conditions.

The Office of Environmental Health & Radiation Safety (EHRS) must evaluate all areas where asphyxiants such as the cryogenic liquids nitrogen, helium, argon and carbon dioxide are stored or used.

If monitoring is required by EHRS only the following monitors may be installed. Portable air monitors shall not be used for continuous monitoring.


The Dråger PointGard 2100 or other Dråger systems

The DrågerSensor O2 # 6809720 should be used in areas where liquid nitrogen, helium and argon are used. It should not be used in high carbon dioxide concentrations. This is a membrane-type galvanic sensor.

The DrågerSensor O2 # 6809630 should be used in areas where liquid nitrogen or carbon dioxide are used.


Dråger recommends Nelson May at Neal Systems Inc., Newtown, Pa 18940, for sales.

Kele OS-1 Oxygen Sensor

The Kele OS-1 oxygen sensor is galvanic and acceptable for use in liquid nitrogen, helium and argon environments.

Contact 877-826-9045 for direct sales.

Note: the Kele OS-1 has a fixed internal sensor with a 3-5 year life expectancy. The complete unit will need to be replaced every 3-5 years.


 The monitor and audible alarm must be located on the outside of the room.

 An internal pump or sensor extension must be used to draw an air sample from the room to the monitor.

 EHRS must approve the placement of the sampling point.


Compressed calibration gas cylinders as recommended by the manufacturer and the corresponding adaptor must be purchased with the monitor.

Initial calibration must be performed as part of the construction project.


EHRS supplied warning signage, indicating a potential oxygen deficient atmosphere, must be adhered to all doors leading into a room with an oxygen monitor.

Signage installation must be part of the construction project.


Revised 6/2022

If you have additional questions, you can contact EHRS during office hours, Monday through Friday, 8 AM to 5 PM call 215-898-4453 or send an email. 

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