Table 1 The new system for laser classification

Class 1

The Class 1 laser is the safest under normal use. These lasers may pose a risk when viewed with a telescope or microscope of sufficiently high aperture

Class 1M

The Class 1M laser is safe during normal use. However, when passed through a magnifying device such as a microscope can pose hazard. A laser falls in this class if the power that can pass through the pupil of a naked eye is lower than the accessible emission level (AEL) for Class 1

Class 2

A Class 2 laser is the visible-light laser (400–700 nm). It is safe as the blink reflex will limit the exposure time lower than 0.25 s. However, intentional holding of the blink reflex could lead to potential eye injury. Several measuring instruments and laser pointers are based on Class 2

Class 2M

This class laser is safe as the blink reflex if not viewed through optical instruments. Similar to Class 1M, this class laser lights are with a large divergence, the light passing through the pupil should not exceed the specifications for Class 2

Class 3A

This laser class is safe if handled carefully. The maximum permissible exposure (MPE) can be exceeded, which is associated with a low injury risk

Class 3B

This class is hazardous if exposed directly to the eye. Protective eyewear must be used where direct viewing is needed or may occur. The equipment with Class 3B lasers must be fitted with a safety interlock and a key switch

Class 4

This class is the most dangerous among all lasers. This laser can cause permanent eye damage or burn the skin as a result of direct, diffuse or indirect beam viewing or contact. These lasers may cause a fire risk as they can ignite combustible materials. Several laser used in scientific, industrial, military and medical applications fall in this category. The equipment with Class 4 lasers must be fitted with a safety interlock and a key switch