What are the class 4 laser safety requirements?

Lasers that fall under the class 4 category are among the most dangerous. They can burn your skin and cause severe, permanent damages to your eyes. So, you definitely want to be properly prepared before you use them.

Let’s overview the main characteristics of the class 4 lasers and their safety requirements.

How lasers are classified

Lasers are categorized in different classes from 1 to 4. The IEC 60825-1 (International Electrotechnical Commission) standard defined the different laser classes.

The IEC introduced a system for the classification of lasers and other products emitting laser radiation in the wavelength range from 180 nm to 1 mm. They are classified according to the hazard they represent for humans. The norm also aims to aid with hazard evaluation and the determination of user control measures.

What is the class 4 laser exactly?

As a guideline, under the old class system, lasers were considered class 4 when their optical power was over 500 mW. There are in fact many applications that use class 4 lasers; laser engraving, 3D printing, and material cutting, just to name a few. 

The higher the class, the more harmful the laser could be, and appropriate safety measures should be followed. Typically, all lasers manufacturers must indicate the class of their lasers, so the end user can then conform to the safety requirements from the governing bodies in his/her country.

What makes class 4 lasers so dangerous?

One can easily conceive that lasers can be very harmful. What people don’t fully realize, however, is that a lot of lasers are not in the visible range, and even low power lasers can cause injury to the eyes or the skin.



A study done by the LIA reports that 71% of incidents when using lasers were related to eyes injuries resulting mainly in blind spot in the field of vision. Most accidents happen in research and development laboratories with unconfined beams either during alignment or through a manipulation in the optical setup while the laser is active.

Also, worth to know, many accidents result from an unexpected upward reflection. Not using eyewear or using an incorrect selection or improper fit was identified as the main cause.

Typically, in the United States, safety guidance is coming from ANSI Z136 standards (American Standard Institute). The LIA (Laser Institute of America) being the publisher of those standards. Class 4 is currently the most dangerous class, with lasers in this category being able to cause severe injuries for the skin and eyes.

So, what are the class 4 laser safety requirements?

In a nutshell, class 4 laser safety requirements are as follow:

  1. First, classifying the laser and laser systems according to their relative hazards and then specifying the appropriate control measures based on their conditions of use as well. Hazard evaluation includes the capability of the beam path, the process interactions between the laser and the surrounding materials, the location of the laser itself, etc. Then a nominal hazard zone needs to be identified which means that a zone where the laser beam may exceed the maximum permissible exposure (MPE) needs to be defined so it can be confined to a limited space so the latter can act as protection to the nearby people.

  2. The institution management has the fundamental responsibility to ensure the safety of the lasers used in the facilities under its control.

  3. The institution must provide a safety and training program for Class 3B and 4 lasers. An individual designated as the Laser Safety Officer (LSO) with the authority and responsibility to evaluate and implement safety measures. Specific duties are listed under Appendix A of the ANSI Z136,1. A laser safety program must be put in place and documented to ensure that laser users have a detailed understanding of the laser risks and hazards so they are enable to use the safety measure in place and also evaluate the required control measure to be selected.

Whenever possible, class 4 laser should be controlled and monitored at a position as far as possible from the beam path to mitigate the risk and hazard.

It may be necessary for the Laser Safety Officer (LSO) to measure the lasers in order to establish the maximum permissible exposure (MPE) values. In this case, you will need to get a high-precision laser beam measurement that you can obtain with an industrial-grade laser power meter in order to get accurate values.

This blog does not pretend to replace the standards listed above. It is up to the user to verify what class 4 laser safety requirements are enforced in your country. There is usually an institution controlling those guidelines in each nation.

Do you have a laser safety application in which the measurement process is critical? Keep Gentec-EO in your mind then and let us know your needs.

Claude Lachance
Vice-President of Sales and Marketing at Gentec-EO
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