Читать книгу Patty's Industrial Hygiene, Physical and Biological Agents - Группа авторов - Страница 135

Various absorptive filter media are available for eyewear to attenuate visible and IR radiation. Sunglasses marketed to airline pilots as protective against blue light exposure were found to provide sufficient protection against the solar blue‐light hazard at flying altitude as well as at ground level (49). Protective eyewear with known attenuation in the blue region should be used for protection against the blue‐light hazard from artificial sources.

Tinted eyewear that does not attenuate light uniformly across the visible spectrum may alter color perception, potentially inhibiting the ability to distinguish color‐coded safety signals and markings. Under the ANSI Z87.1‐2015 standard for eye and face protection (58), visible light filters that transmit 13.9% or more of visible light (and are thus suitable for wearing while driving a vehicle) must comply with the light transmittance requirements of the ANSI Z80.3‐2010 standard for nonprescription sunglasses, which include traffic signal recognition. However, brown‐tinted sunglasses that met the ANSI Z80.3 standard were found to distort color perception among railroad workers in Canada such that yellow railroad signals appeared red to some individuals (59). When color distortion could compromise safety or job performance, a neutral gray tint, which attenuates visible wavelengths uniformly, should be considered when selecting filtering eyewear, provided that adequate attenuation of any blue‐light hazards present can be achieved without excessive darkening of vision overall.

In some cases, extremely high radiant energy absorbed by a filter could potentially raise its temperature high enough for the filter to become a significant source of IR itself, or even to melt. A reflective coating of certain metals such as gold or copper can block some of the radiation from entering a filter, enhancing the filter's performance, though with some reduction in transmission of visible light. Alternatively, interference filters have recently been developed for use in near‐IR protective eyewear that may provide IR reflectance and visible light transmittance similar to that of reflective filters while showing more resistance to mechanical damage such as cracking, scratching and delamination (60, 61).

Reflective aluminized clothing, illustrated in Figure 10, is widely used for protection against radiant heat stress. Barrier creams with reflective flecks are available for application to skin that could be exposed to high levels of IR.