Final answer:
Forklifts in flammable atmospheres should be powered by electricity or explosion-proof engines.
Step-by-step explanation:
In flammable atmospheres, forklifts should be powered by electricity or explosion-proof engines. These power sources eliminate the risk of sparks or flames that could ignite the flammable substances in the atmosphere. Electric forklifts use batteries as their power source, while explosion-proof engines are designed to prevent explosions or fires in hazardous environments.