CDC Guidance for IAQ - Indoor Air Quality


Posted on Monday 22nd February 2021
CDC Guidance for IAQ

Our GREENandSAVE staff has been researching indoor air quality (IAQ). Since COVID-19 is a respiratory disease it is only natural to look at IAQ for immediate and long term sustainability of human life on earth. In many cases, people spend 90% of their time indoors, and this is particularly the case during winter months.

Here is a clear highlight on some of the key Frequently Asked Questions (FAQ) for the Center for Disease and Prevention (CDC), specifically as it relates to the CDC Guidance for IAQ.


The CDC information is on this page:, which includes multiple “Ventilation FAQs”. Here are three of the key FAQs and corresponding responses from the CDC:

CDC Guidance for IAQ – Ventilation FAQ: Does germicidal ultraviolet (GUV) disinfection kill the virus that causes COVID-19?


Germicidal Ultraviolet (GUV), or Ultraviolet Germicidal Irradiation (UVGI), is a disinfection tool used in many different settings, such as residential, commercial, educational, and healthcare. The technology uses ultraviolet (UV) energy to inactivate (kill) microorganisms, including viruses, when designed and installed correctly.

There is still a lot to learn about SARS-CoV-2, the virus that causes COVID-19, and the possibility of airborne viral particles and spread. However, GUV can inactivate viruses in the air and on surfaces*. The design and sizing of effective GUV disinfection systems requires specific knowledge and experience.

Be sure to seek consultation with a reputable GUV manufacturer or an experienced GUV system designer prior to installing GUV systems. These professionals can assist by doing necessary calculations, making fixture selections, properly installing the system, and testing for proper operation specific to the setting.

*Note: CDC’s recommendation for primary surface disinfection in occupied environments is to follow the CDC/EPA guidance for surface disinfection.

CDC Guidance for IAQ – Ventilation FAQ: What are the types of germicidal ultraviolet (GUV) for cleaning and disinfection in the workplace?

  • Upper-room GUV
  • Upper-room (or upper-air) GUV uses specially designed GUV fixtures mounted on walls or ceilings to create a disinfection zone of ultraviolet (UV) energy that is focused up and away from people. These fixtures disinfect air as it circulates from mechanical ventilation, ceiling fans, or natural air movement. The advantage of upper-room GUV is that it disinfects the air closer to and above people who are in the room. Since the 1980s, GUV systems have been widely used for control of tuberculosis (TB). The CDC guidance Environmental Control for Tuberculosis: Basic Upper-Room Ultraviolet Germicidal Irradiation Guidelines for Healthcare Settings provides information on appropriate GUV system design, related safe operation, and maintenance. Based on data from other human coronaviruses, a GUV system designed to protect against the spread of TB should be effective at inactivating SARS-CoV-2, the virus that causes COVID-19, and therefore prevent spread. GUV systems usually require a few GUV fixtures to be effective. For example, a rectangular-shaped waiting room with 10–30 occupants will require 2–3 upper-air GUV fixtures. Of note, the potential for reflection of UV energy into the lower occupied space is a potential safety concern with upper-room GUV systems. However, a reputable GUV manufacturer or an experienced GUV system designer should know the precautionary techniques to prevent harmful UV exposures to people in the space. [Potential Application: Can be used in any indoor environment; most useful in spaces highly occupied with people who are or may be sick.]
  • In-Duct GUV
    In-duct GUV systems are installed within a heating, ventilation, and air-conditioning (HVAC) system. These systems are designed to serve one of two purposes:
    • Coil treatment GUV keeps HVAC coils, drain pans, and wetted surfaces free of microbial growth. These devices produce relatively low levels of UV energy. This energy is continually delivered 24 hours a day, which is why they are effective. Coil treatment GUV devices are not designed for disinfecting the air and should not be installed for the purpose of air disinfection. [Potential Application: Can be used to reduce HVAC maintenance and improve operational efficiency within large, commercial HVAC systems or residential HVAC systems; not recommended for inactivating airborne pathogens.]
    • Air disinfection GUV systems can be effective at inactivating airborne pathogens as they flow within the HVAC duct. HVAC air disinfection GUV systems generally require more powerful UV lamps or a greater number of lamps, or both, to provide the necessary GUV required to inactivate pathogens in a short period of time. Air disinfection systems are often placed downstream of the HVAC coils. This location keeps the coil, drain pan, and wetted surfaces free of microbial growth and also disinfects the moving air. [Potential Application: Can be used inside any HVAC system to disinfect infectious airborne pathogens.]
  • Far-UV (or Far-UVC)
    Far-UV is one of many emerging technologies that have become popular during the COVID-19 pandemic. While standard GUV fixtures emit UV energy at a wavelength around 254 nanometers (nm), far-UV devices use different lamps to emit UV energy at a wavelength around 222 nm. Aside from the wavelength, a major difference between the two technologies is that standard GUV systems are specifically designed to avoid exposing people to the UV energy, while many far-UV devices are marketed as safe for exposing people and their direct environment to UV energy. A review of peer-reviewed literature indicates that far-UV wavelengths can effectively inactivate microorganisms, including human coronaviruses, when appropriate UV doses are applied. Questions remain about the mechanisms of killing microorganisms and overall safety. Far-UV might prove to be effective at disinfecting air and surfaces, without some of the safety precautions required for standard GUV. Far-UV devices are best viewed as new and emerging technology. [Potential Application: Yet to be determined.] Consumers considering an emerging technology such as Far-UV can research the proposed system. Ask the vendor to provide proof of effectiveness and performance that demonstrates a clear protective benefit. Engage with a ventilation engineer, and if the engineer recommends installing such a system, obtain a guarantee as to expected disinfection performance. When evaluating evidence of system effectiveness, place emphasis on research publications over anecdotal claims and consider the following questions:
  • Are there independent studies that prove the desired performance of the technology?
  • Did the study environments represent your environment and intended use?
  • Have performance results been published in a scientific or medical journal?
  • Was the technology evaluated for potential adverse health effects or occupational exposures?
  • Where is the technology being used?


CDC Guidance for IAQ – Ventilation FAQ: Many new air disinfection devices are being marketed for their ability to inactivate the virus that causes COVID-19. How can I tell if they work as advertised?

CDC does not provide recommendations for, or against, any manufacturer or product. There are numerous devices being heavily marketed to provide air cleaning during the ongoing COVID-19 pandemic. Some of the most common are ionization and/or dry hydrogen peroxide devices. Some devices even include both technologies. While variations of these technologies have been around for decades, relative to other air cleaning or disinfection technologies, they have a less-documented track record when it comes to cleaning/disinfecting large and fast volumes of moving air within heating, ventilation, and air conditioning (HVAC) systems or even inside individual rooms. This does not necessarily imply the technologies do not work as advertised. However, in the absence of an established body of peer-reviewed evidence showing proven efficacy and safety under as-used conditions, the technologies are still considered by many to be “emerging.” As with all emerging technologies, consumers are encouraged to exercise caution and to do their homework. Consumers should research the technology, attempting to match any specific claims against the intended use of the product. Consumers should request testing data that quantitively demonstrates a clear protective benefit and occupant safety under conditions consistent with the intended use. Preferably, the documented performance data under as-used conditions should be available from multiple sources, some of which should be independent, third party sources. Unsubstantiated claims of performance or limited case studies with only one device in one room and no reference controls should be questioned. At a minimum, if you are considering the acquisition and use of these devices, you will want to be sure the equipment meets UL 867 standard certification (Standard for Electrostatic Air Cleaners) for production of acceptable levels of ozone, or preferably UL 2998 standard certification (Environmental Claim Validation Procedure (ECVP) for Zero Ozone Emissions from Air Cleaners) which is intended to validate that no ozone is produced.”


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