No. Removing the cause of concern will only lead to deeper concern. You cannot use any fire-powered appliance like a fireplace or furnace without an escape route for the smoke and fumes. If you remove the flue intending to repair or replace it, you should only use the fireplace, wood stove, or furnace once the flue is in working order. If you cannot replace the flue you have removed, call a chimney repair professional immediately.

No, it is not safe to leave a propane heater on overnight. Even if you’re using the heater in a well-ventilated space, the heaters can emit carbon monoxide that can lead to fires. Be sure to fully turn off and secure the propane heater before clearing the area. 

A spark arrestor is a simple metal mesh device that prevents flammable particles from escaping from a combustion source and causing a fire. You typically find these attached to gas or diesel engines on things like cars, generators, and garden tools (lawnmowers, chainsaws, etc.). Fireplace or wood-burning stove chimneys also have spark arrestors attached to or sitting under the chimney cap to capture burning embers.

Start by checking the top or side edge of the door. Look for a certification label or metal tag stamped with details like the fire rating and information on the manufacturer. Even if it’s painted over, the tag should still be visible. Next, look along the edges for slim intumescent strips. They’re designed to swell up and seal gaps when exposed to heat. Finally, check if the door closes itself. Most fire doors have a self-closing mechanism, like an overhead closer or spring hinges. If none of these are obvious, contact a fire safety professional to help verify your door.