Which of the following activities is NOT allowed near flammable materials?

The activity that is not allowed near flammable materials involves operating internal combustion engines. This is because internal combustion engines generate heat and can produce sparks, both of which pose significant fire hazards when in close proximity to flammable materials. The risk of ignition from the heat produced or from potential leaks of combustible fluids increases dramatically, making it essential to avoid operating such engines in these areas to ensure safety.

In contrast, while using electronic devices and hand tools can have their own risks, specific practices or types of tools may be acceptable if they don’t create sparks or excessive heat. Eating food typically does not involve activities that would ignite flammable materials, thus is generally permitted. However, it's always crucial to exercise caution and adhere to safety protocols in environments where flammable materials are present.