Xmas tree is very well-known causing fire hazard. I will never recommend placing a Xmas tree inside your house or its immediate proximity. Should you have inquiries for any fire safety measurements, please contact your nearest local fire station and seek for proper advice.
Here is a youtube link showing how fast a fire could grow on a Xmas tree. Flashover=non-survival, even with the fire fighter's level 2 PPE on (the brown-yellow cloth and breathing apparatus).