The problem of very high protection levels

CO2 and YAG lasers with beam powers above 10 kW are no longer rare. Therefore, when calculating the required protection level according to standard EN 207, a protection requirement of D LB8 and higher occurs more and more frequently for infrared lasers. Theoretically, such a calculation could even result in D LB10. In any case, the standard does not provide for a higher protection level. But do such high protection levels make sense at all?

In the type examination according to EN 207, laser protection glasses must withstand a power density of at least 10^8 W/m² for 5 s at a wavelength of 1070 nm in order to achieve protection level D LB7. With a beam cross-sectional area of 1 mm², this power density is already reached with a laser power of 100 W. If such a laser beam hits the skin next to the laser protection glasses, severe burns are the result. Of course, this applies even more to higher protection levels. Since the protection level is a logarithmic measure, one would have to calculate with 1000 W for D LB8 with the same beam cross-sectional area.

It is therefore urgently recommended not to rely on laser protection glasses alone from D LB7 onwards, but to think about additional safety measures. These could be, for example, not allowing direct exposure by encapsulating the laser and providing the encapsulation with a laser protection window for process observation. Or to provide an interlock that switches off when doors are opened and can thus continue to ensure laser protection. Here, too, the installation of a laser protection window can still guarantee the view from the outside.

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Laser protection, Laser protection filter, Laser protection glasses, protection level, Laser protection windows, infrared laser, OSH

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