Can you safely burn wood in a gas-log fireplace, or coal in a gas-coal fireplace?

I am referring to burning REAL wood/logs or real coal in those gas fireplaces that simulate a wood fire or Victorian fireplace coal grate fire.

I am wondering if there is any risk of gas in the pipes exploding from the heat of the fire if the gas isn’t flowing.

Whereas gas fires make a low maintenance and visually appealing/ambient heat source, the appeal of burning real coal on a coal grate—there’s nothing like it. And a real wood fire is desirable to have in this cold weather. But can a fireplace do both without the gas exploding?