Are GUV lamps safe?

Are GUV lamps safe?

UVGI lamp emissions can pose a workplace safety and health hazard to the eyes and skin if the lamps are improperly used or installed. However, these lamps can be used safely if workers are informed regarding the hazards and follow appropriate precautions. Upper-room GUV has been safely used for preventing airborne transmission for at least 70 years. A great deal is known about the human exposure limits of 254-nm UV (UV-C) irradiation. Compared to the UV-A and UV-B in sunlight, UV-C is almost entirely absorbed by the outer dead layer (stratum corneum) and outer skin (outer epidermis), with very limited penetration to the deeper cellular layers of skin where new cells are constantly created. For comparison, the current daily safety limit of 254-nm UV-C for 8 hours is 6.0 mJ/cm2, whereas less than ten minutes of summer sun exposure at a UV Index of 10 can deliver the equivalent limiting daily safety dose[17] because of its much more-penetrating UV-A and UV-B. A study of continuous monitoring of healthcare workers and patients in an upper-air GUV installation recorded no more than 1/3 of the 8-hour dose. Because it has no outer dead protective layer, the human eye is the organ most susceptible to sunlight and upper-room GUV. Exceeding the threshold level value (TLV) in the lower room will result in painful irritation of the cornea similar to overexposure on a sunny day, especially from sun reflected from water or snow. The damage is painful but transitory, with corneal shedding and replacement in a day or two. When the UV-C source is overhead, the eyes receive very little exposure during normal activities; this is demonstrated in sunlight when the sun is overhead—there is hazardous exposure of the skin but not the eyes. There are no known long-term consequences from an accidental UV-C overexposure.[18] Most eye injuries result from workers on ladders cleaning fixtures or working in the upper room without first turning off the fixtures.[19] For this reason, only trained maintenance workers should be working in the upper room or replacing in-duct lamps. Eye injuries have resulted from insufficient training or improper installation—e.g., workers mistakenly installing an upper-room UVGI fixture upside-down after bulb replacement.[20]

[17] American Conference of Governmental Industrial Hygienists. 2020 Threshold Limit Values and Biological Exposure Indices. Cincinnati: ACGIH; 2020.

[18] International Commission on Illumination (CIE). CIE 187:2010, UV-C Photocarcinogenesis Risks from Germicidal Lamps. Vienna: CIE; 2010.

[19] Sliney D. Balancing the risk of eye irritation from UV-C with infection from bioaerosols. Photochem Photobiol. 2013;89(4):770-6. [Erratum in: Photochem Photobiol. 2013 Jul-Aug; 89(4):770].

[20] Sensakovic JW, Smith LG. Nosocomial ultraviolet keratoconjunctivitis. Infect Control. 1982;3:475-6.