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Oxygen Monitoring


The OUAL has several locations that present an asphyxiation hazard due to oxygen depletion. The primary hazards are due to Sulfur Hexafluoride (SF6) and Liquid Nitrogen (LN2).


The hazards from SF6 are located in 2 locations:

  1. The vault, and especially the pit
  2. The dock

The Pit

The accelerator tank is filled with SF6 at 480 to 650 kPa (70 to 90 PSI). There is a blower, some filters, some dryers, and some piping connected to the tank to keep the SF6 circulated, clean, and dry. It is possible for any of this piping or the tank itself to leak SF6. Since SF6 is significantly heavier than air, it will flow to the lowest point, and gather there, until mixing with the air and dissipating. The pit under the accelerator is the lowest point in the lab. The O2 monitor can be seen from the top of the stairs leading into the pit. A plot of the oxygen readings from the pit can be found at

The Dock

The storage tank and compressor for the SF6 are located in the loading dock. The amount of SF6 stored in the tank is generally much less than what is stored in the accelerator tank. When the tank is open to atmosphere, all of the SF6 is in the storage tank on the dock. The O2 monitor is located approximately 1.5m (5 ft) to the right of the door leading from the lab into the dock. A plot of the oxygen readings from the dock can be found at


The lab/office space in room 115 is where dewars of Liquid Nitrogen (LN2) are stored. Although air is composed of 78% nitrogen, LN2 is roughly 650 times more dense than air. A spill of LN2 can easily displace enough oxygen from a room to create an asphyxiation hazard.

Monitoring Equipment

Equipment Info

Oxygen deficiency is monitored in the lab using 2 AMI Model 221R Oxygen Deficiency Monitors. These monitors were installed in June 2021 by Don Carter and Greg Leblanc. Normal oxygen content is 20.9%. The current oxygen reading will be be displayed on the red LED numbers on the monitor. The monitor should also show a green power LED under normal conditions. If low oxygen is detected, an alarm will sound, and the area should be evacuated, and accelerator staff contacted.

Communication Info

oxygen_monitors.1623702405.txt.gz · Last modified: 2021/06/14 16:26 by leblanc