The oxygen generator of the Navy submarine New Hampshire, a Virginia-class attack boat, failed on March 19, according to a report on the Navy Times. The incident occurred as the sub approached a floating ice station north of Purdhoe Bay, Alaska, and prompted a switch to its backup system, which consisted of oxygen-producing sodium chlorate candles.

An e-mailed statement from the Naval Sea Systems (NAVSEA) Command shared: “U.S. Navy submarines employ redundant systems that provide safe and operationally suitable environments for their crews… At no time was there any elevated risk for the crew of the submarine.”

The New Hampshire was participating in Ice Exercise 2011, along with the Seawolf-class submarine Connecticut. They were working with the Applied Physics Laboratory Ice Station built on an ice floe in the Beaufort Sea, according to the Times.

In addition to the failure of the oxygen generator, the New Hampshire also had condensation that dripped water onto sensitive equipment, according to a report by Reuters. The equipment was covered with plastic sheets, which served as protection from the dripping. On March 24, NAVSEA released the following statement regarding the situation on the New Hampshire: “The submarine incurred other minor habitability issues relating to temperature and humidity levels… These issues have been addressed and also do not affect the safe operation of the submarine.”

The Navy revealed that the oxygen generator in Virginia-class submarines is a low-pressure system that was introduced with that class; earlier subs had used high-pressure generators. This is said to be the first time that a sustained failure occurred, as the system is considered by Navy and industry sources as very reliable.