The US Navy says that apparently an oxygen generator candle blew up?
The Royal Navy submarine HMS Tireless, participating in the Joint U.S. Navy/Royal Navy Ice Exercise 2007 (ICEX-2007) in the Arctic Ocean, experienced an explosion of a self contained oxygen generation candle that killed two crew members and injured one.
A third was injured and flown to Alaska for treatment. The British say he'll be fine. The submarine was up at APLIS (Applied Physics Lab Ice Station) with USS ALEXANDRIA, conducting an ICEX. According to the sub report VADM Donnelly (COMSUBFOR commander) was just up there.
I don't remember any accidents that involved oxygen candle explosions on US subs. However, google shows that Mir had a problem. The British report doesn't say outright that it was a candle,
but the piece of air-purification machinery thought to have failed was fitted as part of an update in 2001.
I find it unlikely that the British waited 16 years after the ship was delivered to install O2 candle furnaces. More likely the offending item is an upgraded Electrolytic Oxygen Generator. Submariners have a nickname for it: the bomb.