I'm just testing to see if this will be the 7th post of mine removed from this thread but also to say that you may have the heading wrong and may wish to consider changing it.
You see it wasn't carbon monoxide that killed two experienced divers, one a very respected commercial diver dispite the headline carbon monoxide heading I suspect taken from a local newspaper.
Now what did kill two experience commercial divers at work, at the same time in 13 feet of water may be an interesting speculation exercise but not wishing to offend the moderators or the rules I will leave it at that. With the exception of one consideration. It was NOT carbon monoxide. Thanks Iain