The thing about Christmas trees is that they are trees—and if they get dry enough, they are less festive emblems than kindling awaiting a spark.
This video from the National Institute of Standards and Technology shows just how serious a fire hazard a dry tree can be. Two faux living rooms appear on a split screen, each with a tree and a timer. The one on the left is a watered, fresh tree; the one on the right is dried out. When a flame is kindled in each, you can imagine what happens.
There were an average of 200 Christmas tree–related fires in the U.S. each year between 2011 and 2015, according to the National Fire Protection Association, and those fires were more likely to be fatal. While the average house fire results in a death one of every 143 fires, the association reports, fires that start with a Christmas tree kill someone in one out of every 32 fires. Read more on how to prevent them at the NFPA.
Correction, Dec. 7, 2017: This post originally misstated that the video was produced by the National Fire Protection Association. It was produced by the National Institute of Standards and Technology.