Laser classes - definition and classification
Safety first - especially when working with lasers. In order to be able to classify the danger emanating from a laser beam, in advance, laser classes were defined. A total of four laser classes from 1 - 4 (and additional subclasses) divide the devices - from absolutely harmless (“inherently safe” = laser class 1) to highly damaging to eyes and skin.
What makes a laser dangerous?
The high temporal and spatial focusability of a laser is useful for material processing, but can be devastating to biological tissues. A laser, which can cut a metal plate, can lead to irreparable eye damage or to the burning (or charring) of biological tissue within a very short time.
The individual laser classes:
Class 1 - Not dangerous
Class 1 lasers are not dangerous under “reasonably foreseeable conditions and during normal operation”. This means that the radiated power is very low or the laser system is encapsulated in a way that no radiation can escape.
For class 1M lasers, the accessible laser radiation is in the wavelength range of 302.5 nm to 4,000 nm. In this laser class, as long as the cross section of the beam is not reduced by additional, optical instruments - such as lenses or telescopes - there is no danger to the human eye. Without optical reduction, the hazard potential of class 1M devices is the same as class 1.
- Barcode readers, for example at supermarket checkouts
For class 2 lasers, the accessible laser radiation is between 400 nm and 700 nm and thus in the visible spectral range. For short-term exposure of less than 0.25 seconds, class 2 lasers are not dangerous to the human eye. Class 2 lasers may therefore be operated without additional protective equipment - as long as it is ensured that the operator does not need to deliberately or repeatedly look into the beam for a period of more than 0.25 seconds in order to operate the laser.
Laser class 2 is the most underestimated laser class, because an interaction duration of more than 0.25 seconds can result in permanent (!) eye damage. The eyelid closure reflex and/or an aversion reaction are not (!) present in red light in 4 out of 5 subjects. Legally and correctly classified laser class 2 laser pointers are therefore not toys and assume responsible use.
- Laser pointers
- Laser spirit levels
- Light curtains
For class 2M lasers, the accessible laser radiation is in the visible spectral range from 400 nm to 700 nm. As with class 2 lasers, operation is not dangerous unless looking directly into the beam for an exposure time of more than 0.25 seconds. When using optical instruments that reduce the cross section of the laser light, similar hazards to classes 3R and 3B may occur.
- Projection laser, for example in laser shows or an exhibition stand construction
For class 3R lasers, the accessible laser radiation in the visible wavelength range is from 380nm to 780nm at a maximum of 5mW, i.e. 5 times more than for laser class 2. This laser class forms the transition between laser class 2 and 3B. These devices are dangerous to the eye! These lasers should only be used by persons who have been informed of the risks. However, the appointment (and training) of a laser safety officer is not required by law.
- Target devices or distance measurement
- Leveling lasers
- Large-scale light curtains
The accessible laser radiation of devices in class 3B is dangerous to both the eyes and the skin. Looking directly into the laser beam must be avoided at all costs. Looking at the laser beam through a diffuse reflector is possible, as long as the minimum distance between screen and cornea is 130 mm, the maximum observation time does not exceed 10 seconds and no directed beam components can hit the eye directly. For the skin, class 3B devices are dangerous if the values of maximum permissible radiation are exceeded.
- Cosmetic lasers
- Show lasers
Laser safety goggles - depending on the wavelength and power of the laser, there are different versions, recommended from and incl. laser class 3, mandatory for laser class 4
Class 4 devices should only be used by professionals. The accessible radiation is extremely dangerous to eyes and dangerous to the skin. Even diffusely scattered radiation can lead to serious health damage here! But that’s not all: The laser beams can also cause fires or explosions. The class 4 laser devices are high power lasers e.g. for material processing, the output power of which exceeds the limit values of accessible radiation for class 3B and is not limited. The emitted laser beam of class 4 devices is so strong that any contact with eyes or skin immediately causes tissue damage. In the private sphere, these lasers may be freely purchased and used at home. However, we strongly discourage use without appropriate experience and training in terms of the safety of you and others! Eye damage can occur up to several hundred meters and, depending on the wavelength, the laser can penetrate window panes without appreciable absorption.
- Laser cutting machines
- Laser welding machines
- Science and research