Comment by mlmilleratmit

This one I actually know -- biohazards depend on more than just wattage -- spot size, wavelength, pulse characteristics, etc, all go into it. I think you really compare them based on the Poynting vector. Disclosure: I'm a GF backer and am a card carrying physicist who had this question on his qualifying exam in grad school. https://www.rli.com/resources/articles/classification.aspx