Q: What is the permitted force to open a fire door? What kind of means can be used to test this onsite?
A: The answer to your question is found in section 188.8.131.52.5 of the 2000 edition of the Life Safety code, which says: “The forces required to fully open any door manually in a means of egress shall not exceed 15 lbf to release the latch, 30 lbf to set the door in motion, and 15 lbf to open the door to the minimum required width. Opening forces for interior side-hinged or pivot-swinging doors without closers shall not exceed 5 lbf. These forces shall be applied at the latch stile. Exception #1: The opening force for existing doors in existing buildings shall not exceed 50 lbf applied to the latch side. Exception #2: The opening forces for horizontal sliding doors shall be as provided in Chapters 22 and 23. Exception #3: The opening forces for power-operated doors shall be a provided in 184.108.40.206.” I am not an expert in the available tools to measure lbs. of force, but a good-old fashion fish scale should do the job. Since you asked specifically for fire doors, I looked at NFPA 80 but did not find anything that would contradict the above section.