Provisions shall be made to enclose Class-3b or Class-4 laser beams whenever possible. Class-3b or Class-4 laser beam paths that cross between optical tables/equipment benches or pass through barriers shall be properly enclosed and prominently marked identifying the hazard. All enclosures shall be compatible with the laser wavelength and beam power. All laser-beam paths shall be maintained at a height either above or below the eye level of standing/sitting persons who may be exposed.
ANSI Z136.1 184.108.40.206 and 220.127.116.11
Laser enclosures, beam stops, beam barriers, and other exposed surfaces shall be diffusely reflective at the laser wavelength used. Surfaces that may create a specular reflection at the laser wavelength shall not be used. Optimally, potentially exposed surfaces should be painted jet black.