The University of Iowa

SAFETYmatters - Are your lasers Registered?


All users of Class 3B and Class 4 laser systems are required to register their lasers with EHS. EHS is responsible for maintaining an up-to-date inventory in addition to performing periodic safety audits on these laser systems. It is important to note that a laser system may contain a Class 3B or Class 4 laser but may not be classified as such. This has to do with the overall risk of a potentially harmful exposure to individuals working with or on the laser system. Considerations include not only the power of the laser, but the accessibility of the beam, system interlocks, built-in beam filtration, etc. Examples of laser systems containing Class 3B or 4 lasers but carrying a lower classification level include certain confocal microscope systems. If you are unsure of the classification of your laser system, a good rule of thumb is to consider whether the beam is accessible to any part of your body (i.e. can the beam hit you in the eye?). When determining the answer to this question, consider not only the direct beam, but the refracted beam as well. There have been cases in which a microscope system containing high powered lasers caused an eye injury due to the refraction of the laser beam from the sample holder. Even though the beam did not appear accessible, the refracted beam was able to cause an injury.

In short, if a Class 3B or 4 laser beam can reach any part of your body, the system is a Class 3B or 4 laser system and it must be registered with EHS.  If you have unregistered lasers, please complete the laser registration form.

 If you are unsure of the laser system classification, contact EHS Radiation Safety staff for assistance.

Eye Protection

All users of Class 3B and Class 4 laser systems must use appropriate eye protection. It is very important to understand that laser safety glasses are not one-size-fits-all. Laser safety glasses are specific to a wavelength or range of wavelengths and ONLY offer protection from those lasers with that wavelength(s). All legitimate laser safety glasses have the wavelength(s) for which they are effective printed on the frame, in addition to an O.D. value. The O.D. value tells the degree to which the unfiltered laser beam is attenuated, in a log scale. For example, a pair of glasses with an O.D. of 4 will attenuate the beam by a factor of 10,000 while an O.D. of 5 will attenuate the beam by a factor of 100,000. EHS recommends laser safety glasses with an O.D. value of at least 3 for Class 3B lasers and at least 4 for Class 4 lasers. Furthermore, laser glasses should be free from cracks, excessive scratches, or other damage which can decrease their effectiveness.


EHS performs periodic audits of labs utilizing Class 3B and Class 4 lasers. The auditor will review the general laser set-up, procedures, safety equipment, signage, staff training, and other safety related items. There are two laser safety manuals posted on the EHS website. Staff should review the manual appropriate to their use of lasers – research or medical; both manuals include the elements to a good laser safety program.