Therapeutic laser systems are an excellent tool for any veterinary clinic, for treating various pain conditions, reducing inflammation, and for deep tissue healing. However, there are many lasers on the market, possessing both pros and cons, and understanding the differences between them can be challenging. Two of the laser systems most prominently utilized by healthcare practitioners are what are known as Class 3B and Class 4 lasers. Both of these laser types have benefits and risks, and knowing which is which is key for your practice.


Laser classification was first established by the American National Standards Institute to outline the differences in power output of a laser system and the hazard it presents to the user and other persons in the immediate vicinity. A common misconception is that Class 4 lasers are a technological advancement to Class 3B lasers. In fact, the Class 4 was the first laser to be used for medical purposes. A few years later, Class 3B lasers were introduced and deemed more suitable for medical purposes due to their viability to heat tissue while not compromising efficacy, therefore making them safer to use on patients. Thus, the classification of lasers simply refers to the power output of a system and its thermal risk to patients.


Traditionally, Class 4 lasers were known as “surgical grade” lasers, as their primary use in medical applications was to induce thermal effects on tissue — e.g. burning, cauterizing, or destroying specific tissues. Class 4 lasers can be used for pain conditions, but the thermal effects must be mitigated. This can be done by lowering the output power into the 3B laser power range, or by increasing the beam diameter (area) to lower the power density (W/cm2) of the laser beam to <500mW/cm2 , the maximum limit for Class 3 lasers for near infrared (200mW/cm2 is the maximum limit for visible lasers).


Class 3B lasers, on the other hand, can be held in direct contact with tissue, indefinitely, without any risk of thermal damage. This is because their power density is low enough not to induce thermal effects to tissue (although therapeutic treatments are generally a few minutes in duration).


Another difference between Class 3B and Class 4 lasers is the power output. Class 4 lasers do indeed offer a higher power output; however, as far as laser applications go, more is not necessarily better. There is an ideal amount of optical power required to bio-stimulate tissue cells, and both laser types are able to deliver this amount.

For further information about the differences between Class 3B and Class 4 lasers, head to the Theralase website ( to read our recent blog post.


Mr. DuMoulin-White is the Director of Business Development and founder of Theralase Technologies Inc. Since 1994, he has been actively involved in the research, development, design and commercialization of Cool Laser Therapy (CLT) lasers used to eliminate nerve, muscle and joint pain, as well as Medical Laser Systems (MLS) used to activate Photo Dynamic Compounds to destroy cancer, bacteria and viruses. Mr. DuMoulin-White is the inventor/co-inventor of dozens of international patents for CLT and MLS technologies, as well as the author/co-author of numerous publications on phototherapy and light-tissue interaction. He graduated from the University of Western Ontario with a Bachelor of Engineering degree in 1986 and has been a registered professional engineer since 1989. He has been the recipient of the Canadian Award for Business Excellence in 1994 and the Popular Mechanics Innovation Award in 2010.


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