Overnight broth simmering

I’m absolutely self aware that I’m just paranoid, but I need answers to help me get some kind of sleep lol. It’s already 1AM and there’s no signs of me allowing myself to sleep.

My partner has a broth simmering on the stove (on the lowest setting - gas stove). He’s leaving it to simmer overnight, but I’ve always been under the impression that it’s extremely dangerous to leave a gas stove running. Our windows have locks, so I can’t even ease my mind by leaving all the windows open.

I currently have a kidney infection, so I’m constantly feeling terrible at the moment. But of course the paranoia kicks in of “but what if this headache/palpitation/etc is from the gas and not the infection”. We had a gas leak at our last property which made me quite sick, so I’m a bit in my own head about it.

I know simmering broth overnight is common, but I’ve never personally done it on a gas stove, especially with every door and window closed. Is this safe?