FM B 1521 means Class B (F) fire door (M), 1500mm wide and 2100mm high;
FM C means Class C fire door!
FM is the abbreviation of fire door, and it also indicates that there is no specified material
For example, steel fire door is abbreviated as GFM
Wooden fire door is abbreviated as MFM
< p>Class C is the fire door grade, with a fire resistance time of 0.5hFire doors are divided into three levels: A, B, and C
The corresponding fire resistance times are 1.5h, 1h, and 0.5h< /p>