According to the National Fire Protection Association (NFPA), more than 200 home fires each year start with a Christmas tree. In this video, NIST fire researchers demonstrate what could happen if a fire starts in a watered Christmas tree vs. a dry Christmas tree. For Christmas tree safety tips, visit the NFPA website http://www.nfpa.org/Public-Education/By-topic/Seasonal-fires/Winter-holiday-safety/Christmas-tree-fires.
More info: https://www.nist.gov/topics/fire