No flame is not good, especially if there is fuel around. If the MRE heater somehow got damp prematurely, could it damage the raft material? I'd have to look at the implications of storing something like that inside a raft for five years. I see the point of wanting to heat liquid for hypothermia victims though.

We were thinking that using body heat to warm the bottled water would be an option. When I was in the Army and first used the MRE's there were no chemical heaters. We would warm them some by putting them in our pockets to help decongeal the grease.

The food ration can be crumbled into the water to make a sweet drink to treat hypothermia if the person is conscious. Body heat could them warm the drink so it would not cool the victim

Tom