Contrary to what Hollywood movies portray, lasers are not powerful enough to obliterate entire planets (looking at you StarWars), but there are still powerful enough to damage your skin and cause serious eye injuries. This is why strict standards were put in place separating laser systems in different safety classes according to their ability to cause hazards.
Let’s ask ourselves a question first: What exactly is a laser? The term was coined in 1959 by Gordon Gould, an American physicist, and the word itself is actually an acronym of “light amplification by stimulated emission of radiation”. Therefore, laser systems produce, by optical amplification, highly-concentrated light beams that are rich in energy. The intensity of a laser system varies according to the industry needs from a harmless laser pointer to an extremely powerful laser-cutting system.
This blog will tackle the mysterious laser safety classes and the laser safety standards, but first we are going to look at the potential health hazards that the use of laser in the industry.
The two main types of health hazards inherent to laser radiation are eye and skin hazards. This is why if the laser system is not Class 1 rated (100% safe), laser safety glasses or even special suits are used by the staff when entering the danger zone of the operating system.
When light reaches the eye, the cornea and the lens act as a sort of amplifier: like a magnifying glass, it concentrates light into a smaller area on the retina (the back of the eye) which, afterward, is processed by the brain as an image. Those three components of the eye (cornea, lens and retina) are the most susceptible to damage from laser radiation.
Without getting too deep into laser physics, all light wavelengths can be harmful to the eyes, but some react differently with the various components of the eye. Most laser engraving machines are in the near infrared (700-2000 nm) and the far infrared (4000 nm - 11,000 + nm ).
For reference, the wavelength of the laser marker of the LXQ series is 1064 nm. For these wavelengths, the retina is especially affected by the laser as the light is not absorbed by the eyes till it reaches the retina. Therefore, the light is amplified further by the lens/cornea before reaching the retina significantly increasing the power output by area (W/m2) of the beam. All this energy is spent burning a small area of the retina which causes blindness and severe eye damages. Photochemical damages is also possible for wavelength lower than 400 nm (in the ultraviolet range) and may cause the development of cataracts (decreased vision).
Direct contact with the laser beam can also cause skin injuries, even if there are significantly less damaging than eyes injuries. The injuries are usually from thermal damages (ever tried touching the stove as a kid? It is similar) or photochemical damages. The importance of the injury is according to the power output and the wavelength of the laser, the size of the affected area and the duration of the irradiation.
Laser standards are an important aspect of laser safety as health hazards are unavoidable if no measures are taken as seen above. Indeed, standards were first made as scientists recognized that even the low power output laser could be a potential danger in the industry.
The classification known as IEC 60825-1 is the current international standard for laser (used by Europe and Canada). The American and European versions of the international standard are named ANSI Z136 and EN 207 respectively. These standards explain the different classes, how to calculate certain laser parameters, the proper labels, safety measures when handling the laser, etc. They also impose upon manufacturers required safety measures like the nominal hazard zone.
Now, we can finally tackle the core of the blog. What are those different laser classes and the distinctions between each one as stated in the standards? To simplify, we are going to use the revised classification system specified by the IEC 60825-1 (note that the old system still used by the United States is very similar).
- Class 1: In all operations, the laser system is safe for viewing. These lasers usually possess a very low power output (a few microwatts), so they are categorized as a Class 1 system. However, higher classes such as Class 3 or 4 for industrial marking systems, have a power output strong enough to burn your skin and blind you, are often reduced to Class 1 by correctly enclosing them (this is called an embedded laser). For example, a laser printer uses a Class 4 laser, but since it is enclosed inside the printer, it is considered a Class 1. There are no precautions in handling it as long as it is not damaged.
- Class 1M: This class is similar to the Class 1 above, which means it is generally safe for viewing with the naked eyes. Viewing the laser with an optical instrument (prescription glasses not included) may be hazardous as the beam is amplified.
- Class 2: Intentionally staring longer than 0.25 second at the laser beam from a Class 2 laser (which means overcoming the aversion response) may be hazardous. So, as long as you don’t fight against your instinct to look away, it should be safe for viewing. It has a continuous power output of less than 1 mW but higher than Class 1.
- Class 2M: Like Class 1M with Class 1, Class 2M must follow the same precautions as Class 2, but with additional hazards if viewed with an optical instrument.
- Class 3R: The risk with Class 3R is higher than the previous classes, but lower than Class 3B. Exposure to this system is considered low risk, but potentially hazardous: Therefore warning labels must identify the Class 3R laser product (higher laser class products have the same requirement). The continuous power level is at 1 to 5 mW.
- Class 3B: Avoiding direct contact with the laser (or the specular reflection of it) is important as it is hazardous to the eyes and the skin. The diffusive reflection of the laser beam is safe. The continuous power output is between 5 to 500 mW.
- Class 4: It is the highest class in term of hazards: Extreme precautions are advised if not correctly enclosed. Contrary to the Class 3B, diffusive reflection of the light is also hazardous. The continuous power output of a Class 4 laser product is so high (>500 mW) that it can ignite materials (that power is what makes them attractive to cutting, marking and welding).
Whatever you use laser for domestic or industrial applications, safety must always be your priority. By following these standards you will make sure to use laser properly.
For those of you using laser in manufacturing process please note that we have an upcoming ebook to help you use laser marking technology safely. Until then you can visit the section of our website dedicated to laser safety and international standards. Enjoy the reading!