Contrary to what this looks like, it is not spider web, but a phenomenon that happens during a fire called a soot web. When synthetic and petroleum based products burn, the particles that remain in the air cling to each other and form these chains that become spider web - like formations. Many people think that the soot from the fire is clinging to existing spider webs, but these actually are completely created from the contents of the fire, and are by no means, indicative of anyone's housekeeping habits.