Thank you, Kourageous Kamille.
I simply couldn't help responding, simply because I actually once had the gruesome misfortune of having been called in by my local PD to examine a water heater in similar condition to this one that had also killed somebody (an elderly woman and her two little dogs, actually). I'm not going to get into the details, but the heater had been installed by the cheapest idiot her son could find in the Want-Ad Digest. He charged half as much as the next cheapest guy, and did his work with bathroom caulk and aluminum sheeting he made from soda cans. She was fine for 6 months until the gas finished melting through the caulk, and then she died in bed. Right next to the little dogs.
Anyway, let the lesson be twofold: 1) Don't trust other people's gas-burning appliances, especially in countries with effectively no building codes, and 2) Any sign of black soot around the exhaust tubing on any interior gas-burning appliance is not an "oops, I'd better look into that soon" kind of deal. It's a "turn the SOB off RIGHT NOW and do NOT use it again until an HVAC tech can look at it!!!" kind of deal.
I bet this unit sprung a major leak the very first time it was used in this configuration. I bet it then struggled along for another year or so, blowing off CO all the while, but the levels never got high enough to kill anybody. People probably had headaches and nausea but blamed it on too many margaritas and the old Montezuma's Revenge, then they went home and felt 100% better. That's very common with rental units with gas leaks, and landlords are usually loathe to hear about "Your condo made me sick, but then I got better, you should check it out". They say "ya huh, it gets checked once a year, no bugs and the linens are clean. Don't drink so much next time."
According to what I've read, the temperature was down in the low 70s on the first two nights that the Sharps stayed in the condo. My supposition is that they closed all the windows and each of them took a hot shower or bath (likely after a long flight from the mainland), with one of them then leaving the hot water dripping (or possibly there was a hot water leak somewhere to produce the same result). This made the water heater cycle on and off multiple times per hour, eventually saturating the condo with CO that (with the closed windows and the AC off) they were in no position to survive.
This last part is pure supposition: I'm no Gil Grissom. But I know for 100% certainty that hot water heater would be cause for an immediate failure of ANY building inspection. It's not merely out of code, it's basically the same as having live sparking wires in your basement ("It's okay, I just don't go near them").
I feel terrible for the family, but I'm glad to have a resource like websleuths to cut through all the misinformation.
