The British Standard sets out seven Classes of laser, these are Class 1, Class 1M, Class 2, Class 2M, Class 3R, Class 3B and Class 4. The higher the Class number, the greater the laser radiation hazard posed by the laser. Class 4 lasers are high power devices, usually needing a mains power supply. Class 4 lasers are used for specific applications in research, medicine and industry. They are also used in the entertainment industry. Class 4 lasers are not designed to be used as laser pointers.
A laser is assigned to a particular Class when the measured emission level exceeds the AEL for all lower laser Classes but does not exceed the AEL for the Class assigned. For example, a laser will be assigned as a Class 3R laser product when the maximum measured accessible emission level exceeds Class 1, Class 1M, Class 2 and Class 2M AEL values but does not exceed the Class 3R AEL. Once a laser has been assigned to a particular Class there are other requirements prescribed in the British Standard which should be met. These will include product labelling and customer information, and may include specific engineering control features to be incorporated in the laser product depending upon the Class assigned. A summary of the laser Classes is given below.
Class 3B: Class 3B lasers may have an output power of up to 500 mW (half a watt). Class 3B lasers may have sufficient power to cause an eye injury, both from the direct beam and from reflections. The higher the output power of the device the greater the risk of injury. Class 3B lasers are therefore considered hazardous to the eye. However, the extent and severity of any eye injury arising from an exposure to the laser beam of a Class 3B laser will depend upon several factors including the radiant power entering the eye and the duration of the exposure. Examples of Class 3B products include lasers used for physiotherapy treatments and many research lasers.
According to the laser classification revised system, the Class 4 is the highest and most dangerous class of laser, including all lasers that exceed the Class 3B AEL. The class 4 green laser pointer is all the green laser pointer exceed the class 3B . The 500mW, 1000mW 1W green laser is class 4 green laser pointer. According to laser classification old system,Class 4 laser have output powers of more than 500 mW in the beam and may cause severe, permanent damage to eye or skin.