The food is part of it, but the heat source must have some involvement. Combustion of gas produces byproducts, no way around it, and studies of camping stoves h

The food is part of it, but the heat source must have some involvement. Combustion of gas produces byproducts, no way around it, and studies of camping stoves have shown the cleanliness of burn is wildly variable depending heavily on basic parameters like the shape of your cookware and the distance from the flame. (For camp stoves, the chief question is carbon monoxide production- if a stove produces low enough levels of carbon monoxide, it's safe-ish to use inside a small tent high on a mountain in a blizzard where you can't cook outside. Climbers have died of CO poisoning cooking in tents, so it is a real possibility)