Sunlight through this glass doorknob started a housefire [1]
by u/Proteon [2] in pics [3]

One reddit user is using their own scary experience to serve as a public service announcement across the internet: be careful of glass doorknobs in your home! The user shared an image of a burnt wall inside their home [4], which was caused by sunlight shining through a glass doorknob and starting a fire. If you're wondering how a doorknob could possibly cause a fire, it's the same theory that explains why fires can be caused by magnifying glasses – thank you, science.

According to the London Fire Brigade [5], "these objects can focus and concentrate the sun's rays sufficiently to start a fire." When the sun's rays become concentrated enough on the glass objects, a fire can be caused by the simple flow of energy. In addition to glass doorknobs, there are other household items you should be cautious of coming in contact with the sun's rays, including glass fishbowls, glass bottles, eye glasses, and more.