Among the most often asked questions in the laser industry is that of the differences between the various laser standards and Classifying Equipment. In an effort to provide some clarity on the subject, the following is presented:

The American National Standards Institute (ANSI) is an organization for which expert volunteers participate on committees to set industry consensus standards in various fields. The ANSI Z136 Committee has published or has under development seven standards specific to the laser field.

The current version of the main ANSI Z136.1 Standard (Z136.1-2000) assigns lasers into one of four broad hazard Classes (1, 2, 3a, 3b and 4) depending on the potential for causing biological damage. Classification is determined by calculations based on exposure time, laser wavelength and average power for CW or repetitively-pulsed lasers and total energy per pulse for pulsed lasers.

Limiting Apertures are dependent on factors such as laser wavelength and are based on physical factors such as the fully dilated pupil size (7mm) and beam “hotspots” (1mm).

For most all exposures to the skin and IR exposures to the eye lasting greater 10 seconds, the involuntary movement of the eyes and the body as well as heat conduction will average an irradiance profile over an area of about 10 mm2, even if the irradiated body part is kept intentionally still. This equates to a size of about 3.5 mm.

Especially in the near-infrared, radiation is penetrating relatively deep into skin and due to scattering, the irradiance profile is averaged over corresponding dimensions. For wavelengths larger than 0.1 mm, an aperture size of 11 mm is specified, as smaller apertures would lead to inaccurate measurements due to diffraction effects.

Different methods to extract valuable metals like gold exist, but Hydrometallurgy Equipment methods are more affordable. Hydrometallurgy consists of leaching-transferring desirable components into solution using acids or halides as leaching agents, purification of the leach solution to remove impurities by solvent extraction, adsorption, or ion exchange, then recovery of base and precious metals from the solution by an electrorefining process, chemical reduction, or crystallization.

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