What's the purpose of a fireplace blower heat sensor/thermostat?

[sofakng]

I'm trying to understand how my (older) natural gas fireplace works and it has a variable speed fan knob to adjust blower fan speed but that's it.

However, I can tell it's wired to a heat sensor/thermostat so even if the blower is set to high it won't turn on until the fireplace is hot. (ie. speed control -> heat sensor -> 110v)

Is this a safety feature or does it serve another purpose?

Is it just to prevent blowing cold air until the fireplace is warm?

 

[Millbilly]

Your fireplace is naturally vented most likely as opposed to power vented. It's designed not to cool the vent at all while it's establishing draft. The ones that don't have a heat switch sometimes have a 5 minute delay.