As an ex-submariner I know that a fire on a submarine when dived or surfaced is a terrifying thing to experience. You cannot simply evacuate a submarine particularly when at sea even on the surface.

I was still serving when these Upholder Class boats were designed and built to replace the older Oberon Class submarines. The Oberon Class proved there worth throughout their long service as did the Porpoise Class boats which looked and were almost identical.

I knew of incidents on these newer boats when they were going through sea trials of sudden flexing of some of the internal tanks, particulary the diesal tank. Obvioulsy a hazard on any boat. There was a case of one boat venting its diesal into an inhabited space.

There were also problems I heard of regarding some of the control systems operated by air and hydraulics.

The boats were mothballed as the RN decided it did not need conventional submarines any more. Buyer were sought and Canada decided to buy.

A submarine is a very complex beast internally and my own thinking of taking a submarine out of mothballs and recommissioning it is that it would not be easy. They had a number of years that though mothballed corrosion and age would set in. I did read that some hull valves were found to be cracked. A cracked hull valve would be a disaster and should one have gone completely it could mean the total loss of a boat and its crew.

I hate to hear of any submariners dying under any circumstance at sea and my sympathy is certainly with the family of the young officer who died. However it is a tribute to the crew and their commander that it was brought under control and that further loss of life was avoided.

Submarines are fitted with what is called EBS, emergancy breathing systems. face masks can be plugged into lines with spigots to take the face mask hose and connector that run throughout the boat allowing one to breath normaly. But it does take time to get them on even if it is just 10-20 seconds as the masks are held in lockers. No reason yet has been given for the cause of the fire but it sounds as though it was in a machinery space, possibly the switchboard area. If that was the case then smoke rapidly fills compartments and inhalation is unavoidable.

At least Canada is an open country and a board of inquiry will establish the cause, unlike here in China where last year an entire crew on a submarine perished and no reason has yet been given though I suspect a lack of training and diesal exhaust getting back into the boat whilst snorting as she was found with the snort masts up on the sea bed and no water inside.

I now only wish that they can get the rest of the crew to safety and then establish a cause.

BTW the new Australian boats the Collins Class were of Swedish design and they too have had many problems but mostly due to noise, not a good thing in the 'Silent Service'.