Safety Tips for Using Germicidal Lamps

What are Germicidal Lamps?

Germicidal lamps emit radiation in the UV-C portion of the ultraviolet (UV) spectrum, which includes wavelengths between 100 and 280 nanometers (nm).  The lamps are used in a variety of applications where disinfection is the primary concern, including air and water purification, food and beverage protection, and sterilization of sensitive tools such as medical instruments.  Germicidal light destroys the ability of bacteria, viruses, and other pathogens to multiply by deactivating their reproductive capabilities.  The average bacteria may be killed in 10 seconds at a distance of 6 inches from the lamp.  The wavelength with the greatest effectiveness is 253.7 nm, which defines the germicidal lamp category with optimized wavelength for maximum absorption by nucleic acids.  Germicidal lamps that generate energy wavelengths shorter than 250 nm (particularly 185 nm) are very effective in producing ozone, which is required for certain applications to oxidize organic compounds. 


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 and animals.

UVR is not felt immediately; in fact, the user may not realize the danger until after 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.