Last Revised: October 12, 2023


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 Hugh Davison at Neal Systems Inc., Newtown, Pa 18940, for sales.


PureAire Monitoring Systems

PureAire oxygen monitors use a long-life zirconium oxide sensor that can last for 10+ years in a normal environment. Visit PureAire for more information. 

Contact Bob Jacobson 


The monitor, audible and visual alarm must be located on the outside of the room so that an alarm can be acknowledged without entering the space. 

A visual indicator of oxygen concentration and alarm must also be mounted on the inside of the room for occupants' observation.

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

The monitor should be hard wired. If this is not possible, EHRS must approve installation and surge protection must be used.

 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.  Calibrations thereafter are required every 6 months and are the responsibility of the faculty or manager.  Contact EHRS for outside service technician recommendations.


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 4/2023

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.