Just to be Safe,I would think the MRE heaters would be The Safest means of Heating up Food/Beverages,In the confines of your Vehicle(Car/Pick-up) without resorting to the use of The Battery,ie.Inverter,Cig.Lighter,etc. Most Surplus stores sell them Individually for a few bucks each!
Doesn't the MRE FRHs use a Magnesium reaction liberating Hydrogen gas. Even carrying MRE FRHs for transport under FAA guidelines is regarded as a transport hazard.
Perhaps the Hotcan or Hotpack self heating meal solution would be even safer as both products use a different exothermic chemical reaction with no explosive hydrogen being released.
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