Answer to Question #2784 Submitted to "Ask the Experts"

Q

We are installing a CO₂ 30W class 4 laser with a wavelength of 10.6 micrometers for purposes of marking a rubber product. I have questions about how to determine the NHZ and if we need to require operators to wear laser goggles. This system has an interlock system and an automatic enclosure but I am concerned about the safety of our operators.

A

If the enclosure contains the entire beam path, you have a Class 1 laser product and the operator, if following prescribed protocols, would not need protective eyewear from the laser radiation. On the conservative side, since CO₂ eyewear is clear it would be easy for the operator to wear laser protective eyewear especially if there is a concern that operators might bypass the enclosure interlocks to remove a jammed part, etc. NHZ generally falls into two modes—one for direct exposure (in your case that could be between 20-50 meters) or for a diffuse reflection (which could be less than 1 meter). Insufficient information was presented to perform a calculation, such as, is the laser pulsed (which in your application I imagine it might be) or continuous? If pulsed, pulse rate, pulse duration, beam diameter, etc., all affect the NHZ. I strongly suggest you obtain a copy of the ANSI Z136.1 Standard Safe Use of Laser; it contains all the information you need to calculate NHZ. 30 W of CO₂ laser power is sufficient to cause major damage to eyes and skin, but also is easy to shield. Polycarbonate panel should work well for diffuse reflections.

Ken Barat
Certified Laser Safety Officer
Lawrence Livermore National Laboratory
National Ignition Facility LSO