According to the national standard, the overall bow of flat tempered glass should not exceed 0.3% and local wave should not exceed 0.2%. The flatness of tempered glass is one of the major indicators of the glass quality.

During the working process of glass tempering furnaces, some major faults may turn up such as sudden power failure, system halt, malfunction of the furnace door caused by air source or mechanical problems, glass breakage in the heating furnace or chiller, glass sticking to the ceramic roller, etc. Measures must be taken in such emergencies, or heavy loss may probably come about.