These fuel cells will warm your food continuously for 6 hours, or provide enough heat to cook for 4 hours straight. To control heat output, simply remove one or both of the fuel cell top lids. As there is no alcohol or mineral wool with formaldehyde, these fuel cells burn clean. They can also be activated multiple times, so you won’t have to use it all just for a quick meal. These fuel cells achieve maximum heat much faster than other fuel sources, letting you cut back the heat time, which means saving more fuel for later use.