Lasers are divided into safety classifications in the US by the American National Standard Identification (ANSI), and globally by the International Electrotechnical Commission (IEC). The classifications below from the revised system (2002) and apply to non-magnified laser devices.
Class I lasers are safe under all conditions of normal use.
Class II applies to only visible light lasers (400-700nm). These devices are considered eye-safe because the blink reflex will limit exposure to less than 0.25 seconds. Intentional suppression of the blink reflex could lead to eye injury. Most laser pointers are class II devices.
IIIR lasers in the visible spectrum have continuous wave (cw) emission of 5mw or less. These devices are considered safe if handled carefully with restricted beam viewing.
IIIB lasers are hazardous to they eye when viewed directly. For visible and infrared devices emission power is limited to 0.5W. Protective eyewear, key switch and safety interlock are required safety features.
Class IV includes all lasers that emit power in excess of IIIB limitations. Eye protection is needed to limit both direct and diffuse reflected exposure. Key switch and safety interlock are also required safety features. The majority of scientific, industrial, military, and medical lasers fall into this category.