I've probably posted about this before.

Periodically, people on the internet talk about locking their very young children (like, under the age of four or five) in their rooms at bedtime. They're usually tempted, but are looking for people to talk them out of it.

And somebody (often several somebodies) is always there to say it's a fire hazard, they wouldn't even close the door all the way, what if the kid couldn't get out in a fire?

I tell you, I do not understand this reasoning at all. I'd prefer to have a dutch door or a baby gate, just for my own psychological reasons (the image of locking a kid up is very disturbing, and I can't quite remove it from my emotional response), but surely it's safer, if there's a fire, for you and the firefighters to know where your child is, instead of having to hunt up and down the house for him or her? Because many parents, I'm sure, would not leave the house without their child, although they probably ought to. And if the kid has left, and the parents can't find them outside... they shouldn't go back in, but what if they do anyway?

As arguments go, I don't understand why people think it's so compelling. If you're really worried about fire safety, it's probably a better idea to clearly mark the kid's door to say there's a child in there, and to maybe invest in some serious fireproofing in your home.