May 19, 2020 UV-C Lamps: Staying Safe
Germicidal UV Safety
Light in the Ultraviolet-C (UV-C) spectrum has proven effective in killing virtually all known microorganisms, making it the ideal solution for cleaning HVAC cooling coils and decontaminating the upper air in public spaces such as schools and hospitals.
However, the potency of UV lamps means that care must be taken when servicing these systems. Unlike some hazards, exposure to ultraviolet light does not offer a natural avoidance response (e.g., squinting eyes in bright sunlight) or a physical cue that protection is necessary (e.g., heat radiating from a hot pan). Furthermore, the physiological effects of UV-C exposure are delayed and can appear up to six hours later.
While damage from UV-C is temporary, user safety is paramount, and the HVAC/R industry takes several precautions to safeguard service personnel from avoidable ultraviolet exposure.
The Power of UV-C
It’s first important to understand the properties of UV-C and how it can pose a threat if handled improperly.
UV light, also known as ultraviolet germicidal irritation (UVGI), comprises a segment of the electromagnetic spectrum between 400 and 100 nm. The UV segment has different sections, labeled UV-A (400 to 315 nm), UV-B (315 to 280 nm) and very high energy and destructive UV-C (280 to 200 nm).
Most of us are familiar with the harmful effects of UV energy transmitted by sunlight in the UV-A and UV-B wavelengths, giving rise to UV “sunburn” inhibitors, or sun tan lotions. We are also familiar with products engineered to withstand the effects of UV radiation, such as plastics, paints, and rubbers. However, unlike the UV-A and UV-B wavelengths, the UV-C band has more than twice the electron volt energy (eV) as UV-A, and it is well absorbed (not reflected) by organic substances, adding to its destructiveness.
This power allows UV-C to break through an organism on a cellular level, effectively scrambling its DNA. UV-C’s effects on the human body vary depending on length of exposure, but can cause painful burns on the skin. It can also cause temporary damage to the cornea if observed directly. Aside from these threats, UV-C is a known carcinogen for human skin.
UV-C Safety Strategies
Therefore, it is essential to follow common-sense safety strategies when dealing with UV-C lamps. The UV-C industry employs several common-sense safeguards to protect HVAC service personnel from avoidable ultraviolet exposure. Some UV-C safety best practices include automatic power disconnects, manual safety switches, and employee awareness training. A UV-C safety program should incorporate:
- Install electrical disconnects/safety switches at all AHU service points to open any access door/panel and automatically de-energize the UV-C system.
- Post warnings on all access panels or doors to a plenum containing UV lamps.
- Install On/Off switches labeled “UV Lights” to provide a manual means of de-energizing the UV-C system.
- Install UV-C safe viewports to allow the viewing of UV-C lamps in operation.
- Lamp/Ballast Monitoring provides continuous current monitoring that indicates system power on/off.
- Use sleeved lamps coated with an FEP (Fluorinated Ethylene Propylene) coating to protect installers against accidental lamp breakage. Products such as EncapsuLamp create a shatter-resistant envelope that captures broken glass, mercury, and other lamp contaminants.
- Never enter the plenum where UV-C lamps are active. If absolutely necessary, personal protective equipment (PPE) should be worn, including UV safety goggles, UV face shields, long-sleeved, tightly woven clothing that covers much of the body, and gloves.
These safety precautions will help ensure service personnel are protected from accidental exposure while maintaining the effectiveness of UVC to eradicate biological contaminants.
As an added value, UV-C’s ability to constantly clean the interior workings of the AHU can extend the equipment’s life for prolonged savings. Biofilms on coil fins hamper their ability to remove heat from the air. If mechanical cleanings are incomplete or ignored, up to 25 percent of cooling capacity can be lost in as little as five years.
When used correctly, UV lighting in HVAC systems and/or the upper air can save energy, raise HVACR efficiency, reduce maintenance and boost indoor air quality.