Frequently Asked Questions on Lasers

The word “laser” is the acronym for Light Amplification by Stimulated Emission of Radiation. Light produced by conventional sources such as lamps radiates in all directions from the lamp and in various wavelengths that reinforce or cancel each other. Light from a laser source is highly coherent and highly directional, and in a specific wavelength. Thus, a laser light can be made to travel in an extremely narrow beam over a vast distance in air without losing much of its energy. 

 Laser can be produced in different “lasing” medium of which there are four common types: 

(a) Solid state (e.g. ruby crystal laser) 

(b) Gaseous state (e.g. CO2 laser) 

(c) Semiconductor (e.g. semiconductor laser) 

(d) Liquid state (e.g. organic dye laser)  

The eyes and skin are the two main organs at risk from exposure to laser beam. Health effects from exposure to laser beam fall into two broad categories – direct and indirect hazards. Direct hazards include injury to the eyes and skin from direct exposure to the laser beam or to reflections of the laser beam from mirrors or metallic surfaces. Various indirect hazards may also arise from the use of lasers, such as electrical hazards, diffuse reflections, burns from heated surfaces, production of toxic fumes, vapours and airborne contaminants from materials heated by the beam.

There are two characteristics of laser light which contribute to the hazard of laser:

· Laser light can be emitted in a narrow beam over vast distances, and does not diminish in intensity with increasing distance from the laser source. This means that the same degree of hazard can be present both close to and far away from the laser source.

Laser pointers are misused when they are directed deliberately at the eye or treated as toys. The light energy from a laser pointer aimed at the eye can be more damaging than looking directly at the sun. In addition, the startling effect of a bright beam of light can cause serious accidents if it is aimed at someone driving a car or operating other machinery or the pilot flying an aircraft. It is to be noted that it is an offence to shine a laser beam at aircraft.

The classification of a laser product provides information on the degree of laser hazard of the product. The higher the class, the more powerful the laser and the greater will be its potential to pose serious danger if used improperly.

It is the responsibility of the manufacturer to ensure that its laser product is properly classified. Lasers manufactured in Singapore are classified into five classes (1, 2, 3a, 3b and 4) depending on the extent of laser hazard. The hazard classifications specified for laser are defined by the output parameters of the laser, i.e., emission wavelength, emission duration, power output, and accessible emission levels (AELs) of laser radiation. The maximum accessible emission levels for various classes of lasers are specified in the Second Schedule to the Radiation Protection (Non-Ionising) Regulations. It should be noted that other countries in the World may adopt slightly different classification schemes.

The classes of lasers specified in the Radiation Protection  (Non-Ionising) Regulations are briefly described as follows:

Class 1 lasers are safe by virtue of their very low power output or by engineering design. These lasers are considered as non-risk lasers, or exempt lasers. The wavelengths could range from ultraviolet, visible to infrared region. Class I continuous visible laser should not have the accessible laser radiation output of more than 0.39 microW.

Class 2 lasers emit visible light and are limited to a maximum output power of 1 milliwatt (mW). A person receiving an eye exposure from a Class 2 laser will be protected from injury by the person’s natural aversion response – an involuntary response which causes the person to blink and turn their head, thereby avoiding further eye exposure.

Class 3a lasers are capable of emitting visible and/or invisible laser radiation up to a maximum output power of 5 mW. For accidental exposure, this class of laser is not capable of damaging the eye immediately, because of the person’s normal aversion response to bright light. However, intentional staring into the laser beam or viewing the laser with optical instruments can be hazardous and should be avoided at all times. Many construction alignment lasers fall into the Class 3a category.

Class 3b lasers are medium-power and moderate-risk laser devices that are capable of emitting ultraviolet, visible or infrared laser radiation. Laser beam from a Class 3b laser can have an output power ranging from 5 mW up to 500 mW for emission duration of longer than 0.25 sec. These lasers are capable of causing temporary and permanent eye injury by exposure from the direct beam or specularly reflected beam. The extent and severity of the eye injury will depend upon several factors including the laser power entering the eye and the duration of the exposure. Skin injury from direct exposure to the laser may also be possible. Therapeutic lasers, acupuncture lasers, bio-stimulation lasers, military laser range finders and designators are all under Class 3b lasers.

Class 4 lasers are high-power and high-risk lasers that are capable of emitting ultraviolet, infrared or visible laser radiation at levels exceeding the accessible emission levels for Class 3b. Typically, these lasers have power output of 500 mW or greater. These lasers can produce a hazardous direct beam or specularly reflected laser beam that can injury the eye immediately (and permanently). They may also burn the skin and/or cut the flesh.

Licences are required to manufacture, sell, possess, use, import and export a Class 3b or Class 4 laser apparatus. Moreover, these licences are also required for laser systems embedded with Class 3b or Class 4 lasers.

The organisation in possession of these controlled laser apparatus will need to apply for an N2 (possession) licence for each laser apparatus. The licence holder will hold the responsibility of ensuring that the laser apparatus is only used by a trained and/or an authorised person.

The person who operates the laser apparatus will need to apply for an N3 (user) licence, authorising him / her to operate the laser. Only authorised users with the N3 licence may operate the laser apparatus, unless an exemption has been obtained from NEA-RPNSG. (Note that a person may be subjected to a written test to demonstrate his / her knowledge in laser safety before being issued the N3 licence.)

Class 4 lasers for application on human beings can only be used by registered medical practitioners at premises approved by MOH. Please be reminded that Class 4 lasers cannot be used in beauty salons, spas or at home.

Any person importing or exporting a Class 3b or Class 4 laser apparatus, or laser system embedded with these laser classes is required to apply for the N4A (import) or N4B (export) licences, respectively. The importer or exporter of the laser apparatus must possess the necessary N1 (dealer) licence or N2 licence before the N4A or N4B licence will be granted. In most cases, the N4A and N4B licences are applied for by the freight forwarding company on behalf of the importer and exporter.

(Please refer to the NEA webpage on Guidelines for Licence Application for more information. For the licensing requirements of entertainment lasers, please refer to the NEA webpage on E-Services and Forms for Radiation Safety.)

You should not.  

Investigation by NEA as well as by radiation protection agencies in advanced countries reveals that a significant proportion of these laser pointers are Class 3b lasers, but improperly labelled as having a lower power output, with lower risk. This is especially so for the green and blue laser pointers. These high power lasers are extremely hazardous and are not suitable for sale to or for use by the general public. 

NEA may check and perform measurement on such laser pointers during the importation process. If such laser pointers are found to have emission powers belonging to those of the Class 3b or Class 4 lasers, then the importers (buyers) will need to apply for licences before the items can be cleared through customs. 

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