Which class of laser has a power greater than 0.5 W and requires controls?

Class 4 lasers are those with a power output greater than 0.5 W and are subject to significant control measures due to their potential hazards. These lasers can cause severe eye and skin injuries and present fire hazards, especially when used inappropriately. Because of their high power and ability to produce hazardous effects, Class 4 lasers necessitate stringent safety controls during operation. This includes protective equipment, restricted access to areas where they are used, and comprehensive safety training for operators.

In contrast, lower classes of lasers, such as Class 2a and Class 3a, have lower power outputs and correspondingly less stringent control requirements. Class 3b lasers can also be hazardous but generally have lower limits on their power output and threat level compared to Class 4 lasers. Understanding these classifications is crucial for ensuring safety in environments where lasers are used.