" Were the passengers inhaling exhaust fumes from passing boats whilst having lunch? Or from the pizza oven?
Just as plausible as the other theories going around! "
In my new career teaching RPL, PPL, CPL and ATPL theory we do make students very aware of the dangers of Carbon Monoxide poisoning:
CO is very insidious and not easily detected -
"The affinity between hemoglobin and carbon monoxide is approximately 230 times stronger than the affinity between hemoglobin and oxygen so hemoglobin binds to carbon monoxide in preference to oxygen."
If anyone is exposed to CO the most obvious telltale is that lips and fingernails turn bright red.
Smoking, fireplaces, badly maintained gas heaters and FW190s all produce large amounts of CO. (that's apparently why FW190 pilots always wear an oxygen mask)
I have a niece that works at 000 and every winter they process several calls for families suffering from the problem.
Even 100% oxygen for several hours does not always end well for victims. The best solution apparently is to place them in oxygen hyperbaric chambers for many hours.
These are becoming more common in Australia these days as high level athletes and their teams use them to speed recovery from injuries.