May 01, 2020 Upper Air UV-C – Improving Indoor Air Quality
For nearly a century, UV HVAC technology has proven to be one of the most reliable and efficient means of keeping indoor air clean and germ-free.
Add to this the 20% energy saving potential that can be realized with UV-C’s ability to clean and maintain cooling coil energy efficiency, and it’s no surprise why the technology is the best means of keeping HVAC systems operating at peak performance.
Upper-room UV-C systems (also known as upper-air) have been used to control airborne infectious diseases and improve indoor air quality since the 1930s.
Nearly a century of research and real-world applications have proven the efficacy of the 253.7 nm germicidal wavelength to disinfect room air simply, safely and quickly without using chemicals.
Upper-room UV-C fixtures utilize the natural rise-and-fall of convection or mechanical air currents to lift airborne infectious agents overhead, where they are exposed to UV-C irradiation and inactivated.
How does it work?
Infectious particles typically move from the lower part of a room to the germicidal zone in the upper room.
Upper-room UV-C systems have been used to control airborne infectious diseases in high-traffic areas and where people congregate since the 1930s. Upper-room UV-C fixtures utilize the natural rise-and-fall of convection or mechanical air currents to lift airborne infectious agents overhead, where they are exposed to UV-C irradiation and inactivated.
Airborne droplets containing infectious agents can remain in room air for at least three hours. Operating 24/7/365, UV-C and upper-room germicidal is a well-established technology that has proven effective as a public health intervention to prevent the spread of airborne diseases [2,3].
Complete microbial inactivation occurs through the cumulative effect of exposure over time as infectious particles are carried repeatedly to the upper room. Each pass inactivates the infectious particles until their concentration in the lower part of the room are effectively diluted.
How do I choose an upper air fixture?
UV Resources offers TWO types of upper-room UVGI fixtures for spaces ranging from 150- to 1,500-square-feet:
- Baffled or louvered-style luminaries. The GLO-150, -225 and -310 are ideal for rooms with ceiling heights between 8-12 feet tall. Non-reflective louvers direct UV-C energy outward and upward to prevent germicidal energy in the lower (occupied) portion of the room or area.
- Open-style luminaries. The GLO-900 and -1500 are ideal for taller spaces with ceiling heights above 12 feet. The traditional baffle system is replaced by an adjustable extended “director” on the bottom of the fixture, which protects room occupants from stray UV-C.
Both types of GLO fixtures from UV Resources—Open and Louvered—provide the industry’s greatest amount of UV-C energy by boosting UVGI output via an exclusive, computer-designed, high spectral, parabolic, aluminum reflector system that significantly reduces internal UV energy losses.
What advice exists for upper air UV-C?
The designer needs to know how many fixtures to use, and where they should be located. Guidelines are published by the CDC and in several peered reviewed papers. Most manufacturers offer guidelines that are based on the latest recommendations of UV-C energy at different distances, this is the most accurate method. Upper room fixtures are used in rooms with ceiling heights of 7 feet and higher. Original guidelines recommended 30 watts of UV lamp power for each 200 sq. ft. of floor area. That has been replaced by the much more accurate method of microwatts of UV-C energy at various distances from the fixture. This best determines the number and placement of fixtures to cover the upper room.
What does an upper-room UVGI installation cost?
From a cost standpoint, UV-C is among the most affordable infection mitigation strategies. Upper-room germicidal fixtures can be installed at roughly $6.00 to $6.50 per-square-foot of treated area. The annual cost of electricity per efficient fixture is $22 per year, assuming 25 watts per fixture, 24 hours per day, and $0.10 per kWh. Lamps are replaced annually at a list price of $43 per lamp.
What is the future of upper room UVGI?
Per ASHRAE’s “Position Document on Airborne Infectious Diseases”, upper room UV must become a common feature of buildings. Upper room UV is effective against all types of viruses and bacteria, including those used for bioterrorism. The technology is well-researched and developed. It’s been shown to be quite effective in all studies of representative environments and it’s easily retrofitted in many building types, including hospitals, health clinics, urgent care locations, childcare facilities, colleges, prisons, jails, virtually all building types. Its cost effectiveness supports its use over the alternatives of dilution and filtration. The foregoing facts support the value of using upper room UV-C for infectious diseases such as colds and flu and all other infectious agents.
 Van Doremalen, N., Bushmaker, T., Morris, D. H., Holbrook, M. G., Gamble, A., Williamson, B. N., … & Munster, V. J. (2020). Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1. New England journal of medicine, 382(16), 1564-1567. Retrieved from https://www.nejm.org/doi/full/10.1056/nejmc2004973
 Nardell & Nathavitharana (2019) Nardell E, Nathavitharana R. Air disinfection in measles transmission hotspots. Lancet. 2019;394(10203):1009–1010. Retrieved from https://pubmed.ncbi.nlm.nih.gov/31495498/
 Mphaphlele et al. (2015) Mphaphlele M, Dharmadhikari AS, Jensen PA, Rudnick SN, Van Reenen TH, Pagano MA, Leuschner W, Sears TA, Milonova SP, Van der Walt M. Institutional tuberculosis transmission. controlled trial of upper room ultraviolet air disinfection: a basis for new dosing guidelines. American Journal of Respiratory and Critical Care Medicine. 2015;192(4):477–484. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4595666/