The air down there

At 9 a.m. last Wednesday, an alarm bell, strobe lights and announcement to evacuate filled the underground laboratory. In a real emergency, researchers and others would have evacuated the area. This, however, was a scenario designed to test the nine oxygen sensors in the Davis Campus, so the researchers calmly continued their work. 

Most of the experiments at Sanford Lab require the use of cryogens, including liquid nitrogen, to purify work spaces and cool materials used in detectors. An inert gas, nitrogen makes up nearly 80 percent of the Earth?s atmosphere. When liquid nitrogen is released rapidly in an enclosed space, it can replace oxygen, creating a hazard. 

Ideally, air should contain 20.9 percent oxygen, said Jaret Heise, Science Liaison Director. However, over time sensors can ?drift??up to a half of a percent yearly. ?We regularly calibrate oxygen sensors to ensure they are operating as they should. More importantly, we want to ensure personnel are safe.?  

If oxygen levels reach 19.5 percent, a local alarm broadcasts within earshot, said Dana Byram, Experiment Support Scientist. At 18 percent oxygen, a facility alarm would tell staff to evacuate the area. ?We purposely put all sensors into this state to verify they are working correctly,? Byram said.

An important component of the testing is to determine how the air handling system will respond, said David Taylor, Experiment Review Engineer. ?Our system is set so that if oxygen should drop to 18 percent, the air handler system would switch to 100 percent fresh air.? 

The Sanford Lab also does bi-weekly drills designed to walk people through the correct response to a potential emergency. ?It reinforces site-specific training,? Heise said. ?Our researchers cycle in and out. That frequency ensures everyone knows how to respond.?

Heise praised staff members involved in the most recent scenario, including Byram, Taylor, Facilities Technicians Shane Heydon, and Oren Loken, Electrical Project Engineer Paul Bauer, and Operations Tech Support Jim Hanhardt. 

?This is a good example of how the lab supports science,? Heise said.