You might catch a tiny whiff of gas right after you turn it off. That’s perfectly normal. It’s just the leftover gas in the line saying goodbye. Do not panic. Open a window for a minute if you’re twitchy.
If the smell doesn’t fade in a few minutes, or if it’s overpowering—like a gas station fell over in your living room—call a professional. But usually, it’s just a polite puff of air. You’re fine.
When Should You Absolutely NOT Do This?
If you smell gas before you touch anything, stop. Do not turn knobs. Do not light a match. Do not even look at the fireplace suspiciously. Get everyone out and call your gas company. Better safe than sorry, my friend.
Also, never turn off the pilot if you plan to light it again within a few hours. Relighting it is a chore involving a long lighter, patience, and maybe some colorful language. Save yourself the drama.