Were the tongues at Pentecost real fire?
No. The tongues at Pentecost were not real fire. The text describes 'cloven tongues like as of fire,' a visible appearance resembling little flames, but it does not say it was fire; it did not burn their hair. They were separated tongues, like fire in appearance only.
Les explains that the Holy Spirit came invisibly, like wind that cannot be seen but whose results are felt. To give the believers something visible, there appeared cloven tongues, meaning separated, like the split hoof of sheep or cattle. He stresses the text says "like as of fire," not actual fire—it did not burn their hair—so they were only flames in outward appearance, and it sat upon each of them. Then they were all filled with the Holy Ghost and began to speak with other languages.