The homeowner/landlord owes duties to their tenants (basically anyone who pays to rent the premises for any duration of time) to maintain safe property; they warrant by renting the property out that the appliances are safe for ordinary use. If the homeowner/landlord hired an outside company and relied on their expertise the liability may be split or shift if a jury finds it reasonable for the homeowner/landlord to rely on those experts assurance of safety. So if a maintenance company was used and the homeowner relied on them, a jury could put the blame on the company rather than the homeowner. Similarly, if the gas company did an inspection and failed to follow policy they could be found jointly liable as well. IMO this family's estate has a negligence and wrongful death claim against multiple parties, including the homeowner/landlord, any maintenance company or individual, any company or individual that installed or worked on the hot water heater, and possibly the local gas company if they had done a recent inspection or turn on of the gas line. JMO as an attorney in the US, I am not licensed anywhere in Mexico.
O/T but a personal case that is similar:
My firm had a case where we sued a homeowner/landlord who rented a property out to a gentleman and his girlfriend. They both passed away their first night in the house, before even moving all of their belongings and furniture in, due to CO poisoning from the space heater. The estate of the deceased sued the homeowner and the gas company who turned the gas back on to the house (the prior renter had only used electric). In our case the homeowner/landlord had actually installed the space heater himself, rather than hiring an outside company or individual, otherwise we would have sued that company or individual too. Turns out at some point the gas vent on the roof had been nailed down, completely sealing it and trapping all gas within the house. So we also attempted to discover the roofing company who had done work on the roof (the nails on the vent cover were identical to the nails on the roof repair) so we could also name them in the lawsuit, but we never discovered which company it was since the homeowner actually ended up passing away from natural causes shortly after the lawsuit started.
We filed suit against the homeowner stating that he should have checked the ventilation line before installing and lighting the space heater, that any reasonably prudent person in that situation would have checked for defects; and against the gas company stating their policy, which specifically required the person turning on the gas line to check the ventilation line before connecting the gas, was violated. The case settled prior to trial and both parties paid into the estates of the deceased.
