IN ROOM

Pros and Cons of Direct Dosage vs Fan Based Systems: Irradiating pathogens does not happen instantly. Disrupting the DNA of microorganisms such as viruses can take up to 100 seconds, subject to germicidal UVC dosage levels. Fan based devices come in many shapes, sizes, and price points. Some of them are designed to be placed on the floor or a counter, while others are designed for ceiling installation. Regardless of the form factor and location, fan-based devices typically draw air into the equipment, partially treat it, and exhaust it without fully irradiating the pathogens. The cycle then continues. With these types of devices, the air speed passing the UV or UVC luminaire is a key factor in addition to the wattage of the luminaire relative to the number of pass-by air intervals needed to fully kill the pathogens. For a 10’ x 12’ room with a 9’ ceiling (approx. 1,000 cubic feet), it may take 15 minutes or more to clean the air in the room. Plus, the sides and corners of the room farthest from the fan device is treated less acutely than the air near the device. By contrast, direct dosage devices, such as the upper air wall mounted technology described on this page, can irradiate all of the air in the same size room within 5 to 7.5 minutes. This is due to the fact that code compliant HVAC systems in rooms, such as dental operatories, have 8 to 12 Air Changes per Hour (ACH). The air moves slowly around the room and across the ceiling giving the UV time to kill the pathogens rather than rushing it by the UV elements inside of a fan-based device. The result is faster and more thorough air disinfection with direct dosage. There is a place for fan-based devices or in-duct devices for properties such as office buildings that do not need acute disinfection. Dental operatories and other healthcare facilities warrant the most aggressive form of pathogen irradiation, as do certain quick serve restaurants and other facilities with high traffic of different people moving though the space.

UVC and UV: Not all ultraviolet wavelengths are created equal when it comes to irradiating pathogens. Ultraviolet-C (UV-C) is between 100 and 280 nanometers (nm). UVC has been proven to have an incredibly high capacity to kill pathogens, including viruses. UV is a broader range 100-400nm, and 405nm is just outside of UV and is used by some manufacturers. The 405nm wavelength has demonstrated capacity to reduce the mitigation of some viruses, but it is not as potent as UVC. Remember that time, intensity, and distance = dose. While the number 405 is higher than 100-280, the intensity is inverted. The devices described here use 253.7nm, which is the peak performance for germicidal effectiveness. (See chart below and ASHRAE Report 2020-2017). When considering a UV or UVC device, ask your potential service or technology provide about the nanometers used in the equipment. Facilities with acute needs such as dental operatories and other healthcare facilities warrant germicidal UVC light, as do certain quick serve restaurants and other facilities with high traffic of different people moving though the space.