>what else could knock you out so fast you had no time to react<
Well thats the real danger with CO2 poisoning.....Very often it is NOT a quick killer,and the signs and syptoms being 'flu like' are readily dismissed by people :(
In a Holiday enviroment especially I guess folks may be more inclined to blame the signs and symptoms,Migraine, Head achey,dizzy,upset stomach,muscle pain and cramps,lethargy...on a bit of "Holiday tummy" and Heat stroke than the are to presume CO2, and so continue to expose themselves over days/weeks,unwittingly.
It can takes days even weeks to kill depending on the PPM, 50PPM being HSE safety standard (=0.05%) it takes up to 800 PPM for Dizziness, nausea, convulsions within 45 minutes, and insensible in 2 hours to occur then 1,600PPM for death in 2 hours, these are levels that would not be attained by a faulty appliance in one hit.
On the signs and Sypmtoms though..I always teach that the Classic recognition combined with all other signs and sypmtoms is the RED flush to the face, I would have thought that would have been evident in the parents given the time frame.
I suspect..though hope Im wrong there was some 'damage limitation' going on by Greek officials more concerned over affects to tourism??? tragic... :(