UVC SAFETY
Hazards & Risks
Minimise Exposure
- Never view the UV lamp directly – at any distance
- Keep exposure time to a minimum and keep as far away from the source as practicable
- Turn off UV lights before working in the BSC
- Restrict access to those personnel who are directly involved with the operation of the UV source.
- Do not loiter near the cabinets.
Hazard and Risks from Germicidal Lamp UV Radiation
UV radiation (UVR) used in most germicidal bulbs is harmful to both skin and eyes, and germicidal bulbs should not be used in any fixture or application that was not designed specifically to prevent exposure to humans or animals. UVR is not felt immediately; in fact, the user may not realize the danger until after the exposure has caused damage. Symptoms typically occur 4 to 24 hours after exposure. The effects on skin are of two types: acute and chronic. Acute effects appear within a few hours of exposure, while chronic effects are long-lasting and cumulative and may not appear for years. An acute effect of UVR is redness of the skin called erythema (similar to sunburn). Chronic effects include accelerated skin aging and skin cancer. UVR is absorbed in the outer layers of the eye – the cornea and conjunctiva. Acute overexposure leads to a painful temporary inflammation, mainly of the cornea, known as photokeratitis. Subsequent overexposure to the UV is unlikely because of the pain involved. Chronic exposure leads to an increased risk of certain types of ocular cataracts. Working unprotected for even a few minutes can cause injury. It is possible to calculate the threshold for acute effects and to set exposure limits. It is not possible, however, to calculate threshold for chronic effects; therefore, because no exposure level is safe, exposure should be reduced as much as possible. Example of biosafety cabinet with germicidal lamp 2 10 CFR 851 mandates the use of the threshold limit value (TLV) exposure limits established by the American Conference of Governmental Industrial Hygienists (ACGIH). The exposure limit for a germicidal lamp is 6 millijoules per square centimeter. At this level, detectable molecular damage appears to be fully repaired within 24 hours. For the case of continuous exposure for longer than 8 hours, such as is possible for a 10- to 12-hour extended shift or a double shift, special care needs to be taken.
Administrative Control
- Never view the UV lamp directly – at any distance
- Keep exposure time to a minimum and keep as far away from the source as practicable
- Turn off UV lights before working in the BSC
- Restrict access to those personnel who are directly involved with the operation of the UV source.
- Do not loiter near the cabinets.
Consult the manufacturer’s manuals for specific information about the potential exposure level and frequency of radiation, as well as the suggested operating protocols. An appropriate combination of engineering and administrative controls should be implemented, and appropriate personal protective equipment (PPE) should be worn, to ensure that the risk to health and safety from UV exposure is low. These must be documented in the Work Planning and Control system and Activity Manager
UVC Light Technology
Application Areas
Limitations for Use of Germicidal Lamps
n a BSC, UV light is not penetrating. Microorganisms beneath dust particles or beneath the work surface are not affected by the UV irradiation.
Bulbs should be wiped on a monthly basis with a soft cloth and dampened with ethanol after the bulb cools down.
UV intensity is significantly reduced by dust-covered lamps and the interior of BSC cluttered with equipment.
UV lamps should be checked periodically with a UV meter (approximately every six months) to ensure that the appropriate intensity of UV light is being emitted for germicidal activity. The amount of germicidal wavelength light emitted from these bulbs decreases with age, and bulb ratings may vary by manufacturer.
254 nm radiation can directly interact with plastics and cause crazing and potential weakening. This can be eliminated using good BSC practices, specifically, by minimizing the amount of material left in a cabinet.
Humidity adversely affects the effectiveness of UV. Above 70% relative humidity, the germicidal effects drop off extremely.
Optimum temperature for output is 77°F–80°F. Temperatures below this optimum temperature range will result in reduced output of the germicidal wavelength. Moving air tends to cool the lamp below its optimum operating temperature, which results in reduced output.
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