Prometheus 6

At 15 percent oxygen, it's safe for humans to enter.

Oh, hell, YOU'RE no fun... 

Data Centers Breathe Easier with Less Oxygen
Jeremy Kirk, IDG News Service
Friday, March 16, 2007 12:00 PM PDT

As data centers become hotter and more dense with servers, a greater chance for fire exists. But there's equipment on the market that applies a well-known method of halting fire: starving it of oxygen.

Only a few vendors are offering oxygen-deprivation systems, but interest in the technology is growing. It involves pumping air that has such a low oxygen content that a fire can't start in the data center.

Air is composed of about 21 percent oxygen, 78 percent nitrogen and 1 percent of other gases. Fire needs the oxygen to burn, and lower percentages of oxygen makes it more difficult or impossible for fire to start.