Recommendations for the use of laser pointers
Nowadays, laser pointers are frequently used as an alternative to the traditional pointer, to make indications in projecting images or information on a screen, for example in training sessions. They are mainly used in the field of education, although they are increasingly being used in various private activities.
As the technical work equipment that they are, they are subject to the legislation on the safety of devices when they are marketed and to the regulations on “laser beams” regarding their use.
The laser incorporated in these pointers is a laser semiconductor which, depending on the glass, radiates with a wavelength corresponding to red or green. The European standard applicable by the manufacturer of these devices is EN 60825-1 on “Safety of laser equipment”. According to this standard, for laser pointers in the visible wavelength range (400-700 nm), at most a class 2 laser can be used. In this class, the maximum admissible power is 1 Mw.
The protection against radiation in class 2 lasers is guaranteed by the reflection of the eyelid when the eye is exposed to radiation. That is to say, a person who takes the laser beam directly to the eye, takes an enlightenment and closes the eyelids. This reaction takes at most 0.25 seconds and is sufficient for protection in the case of class 2 lasers. In any case, it has to be checked that the permissible power density limit value of 25 mW/m2 complied with, which results from a power of 1 mW over the normal diameter of the iris (7 mm). In any case, you must not intentionally look at the beam, as in this case the admissible limit would be exceeded.
Consequently, these laser devices must be marked “laser radiation, do not look into the beam, laser class 2 according to EN 60825-1”.
In the case of class 3 lasers, these are extended lasers, which in the visible wavelength range must comply with the same limit value for direct observation. However, due to the magnification of the beam, these lasers can be dangerous when using optical instruments such as magnifying glasses, microscopes and binoculars. For this reason, these devices must be marked “laser radiation, do not look at the beam, also not with optical instruments, laser class 3 according to EN 60825.1”. The corresponding limit values are:
- p < 5 mW measured with 16 mm diaphragm (25 W/m2)
- p < 1 mW measured with 7 mm diaphragm (25 W/m2)
In non-European countries, radio frequencies are often classified according to a United States CDRH guideline. Class 3A of this directive corresponds to 3B according to EN 60825-1, as it does not need to comply with the 25 W/m2 power density limit value. For this reason, North American scientific publications have described some cases of retinal damage caused by these laser devices. The reason is that they exceed the power of 1 mW, measured on a 7 mm diaphragm, i.e. they exceed the power density of 25 W/m2 and are therefore class 3B lasers.
Class 3B lasers are dangerous, as the automatic blinking reaction of the eyelid to protect the eye is no longer sufficient. This class is not authorised for use in laser pointers. For this reason, the corresponding protection measures must be adopted in the field of research:
- Protective goggles.
- Shielding.
- Safety instructions.
- Signage.
These necessary measures clearly show that class 3B lasers cannot be used for training purposes. Class 2 lasers must be used with written instructions on their correct use, with the following content:
- What kind of laser it is.
- It must not be directed at people.
- Type of batteries to be installed.
When purchasing a laser pointer it is necessary to ensure that it is correctly classified as a class 2 laser according to the EN 60825-1 standard. The information provided must include the manufacturer’s name and address.
At present, there is no “CE” marking on these products.
Further information
*Adaptation of the text of the University of Bristol.
The erroneous use of laser pointers of any kind can cause, directly or indirectly, a serious injury. Its improper use will constitute a disciplinary offence.
The laser pointer must be clearly marked with its category in the classification and class 3A laser pointers must be registered in the laser database of the University’s Office of Safety, Health and Environment (OSSMA). Registration will be limited to staff members (PTGAS and teaching staff) and students who have to use it according to the instructions of their department.
Classes 2 and 3A
The points taken in teaching can cause serious and irreversible damage to the skin. In order to avoid this, the following safety rules must be complied with:
- The projection of the pointer directly at the audience must be considered a risk.
- Under no circumstances should the pointer be directed at the audience.
- If possible, the room where the laser pointer is being used should not be completely darkened.
- A visual inspection should be carried out prior to the presentation to ensure that there are no reflective objects that could project the beam towards the audience or the speaker.
- Class 3A lasers must not be capable of being activated by accident or error, and in the event that this is possible, the pointer must be modified so that it functions safely.
- In the event that the speaker or any member of the audience receives an exposure of the laser beam to the eye, it shall be considered as an accident. The accident will be attended to at the corresponding Medical Service and the OSSMA will be informed of the incident.
Classes 3B and above
The registration and use of these types of pointers for teaching purposes is not permitted.