If chemical disinfectants are used, they should only be applied with the HVAC system turned off. In addition, disinfectants should not be applied to ventilation filters before continuing to use the filters within ventilation systems. The effects of disinfectants on filter performance are unknown. Filters should only be treated with disinfectants if they are to be removed from service and disposed of.
While UV systems are quite effective at maintaining the cleanliness of HVAC coils, drain pans, and other damp surfaces, properly designed systems can be quite effective in inactivating microorganisms in moving air streams on the fly. These systems generally require more lamps, so they can provide significant UV doses in a short period of time. A typical one-pass inactivation efficiency is 85%, just like a good particulate filter, but systems can also be designed for inactivation greater than 99.9%. In addition, a well-designed UV air disinfection system within an HVAC system, and located adjacent to the cooling coils, can also provide the surface disinfection benefits mentioned above.
Another way to install UV is in a “top air” configuration. Specially designed wall-mounted fixtures create an irradiated area above the occupant and disinfect the air in the space, as the air circulates naturally, mechanically or through the HVAC system. CDC has approved this type of system for use in tuberculosis control for nearly 20 years, and there is guidance from NIOSH on how to design them. Finally, mobile UV systems are frequently used for terminal cleaning and surface disinfection in healthcare facilities and other spaces.
Systems such as these are commonly used in unoccupied spaces due to occupant exposure concerns. The three types of systems can be relevant, depending on the type of building and the individual spaces within the building. The design and sizing of effective ultraviolet disinfection systems can be a complex process due to the need to determine the dose delivered to a moving air stream or to an irradiated region of a room. In-duct systems are further complicated by the configuration of the air handling unit and ducts and surface reflections that can help achieve higher irradiation levels.
Overhead air systems require proper air mixing to function properly while paying close attention to reflective surfaces that could cause room occupants to be overexposed to UV energy. Accredited manufacturers and system designers can help by making the necessary calculations and designing specific systems for individual spaces. With more than 57,000 members from more than 132 countries, ASHRAE is a diverse organization dedicated to promoting the arts and sciences of heating, ventilation, air conditioning and refrigeration to serve humanity and promote a sustainable world. What you need to know to keep you and your building safe Can building air filtration protect me from contracting COVID-19? What filter should I use to protect people in my building from COVID-19? Why shouldn't you use the most efficient filter you can find? I know hospitals have good filtration, why don't we all use systems like these? What about ultraviolet (UV) lamps? Do they work? What about portable air filters Doesn't filtration require droplets that cause COVID-19 to be in the air? I've heard that these are large droplets, what precautions should I take when changing filters? What about ionizers, ozone generators, plasma and other air cleaning technologies? Where can I go for more information? Hospitals (and many health centers) have specially designed mechanical systems that can adapt to the levels of filtration they need.
They are often based on other control systems and strategies (e.g. Most importantly, they have dedicated staff who operate and maintain this equipment to provide maximum benefit. What about ultraviolet (UV) lamps, do they work? This filter is what keeps the air in your home or office as clean as possible. Can we help stop the spread of COVID-19 by using better filters? We're going to find out.
The COVID-19 virus attaches to droplets that are released when a person coughs or sneezes. These atomized particles range in size from 1 to 100 microns, so any filter with a Merv 9 rating or better would be effective at trapping them. ASHRAE currently recommends using a minimum MERV 13 filter, which is at least 85% efficient at capturing particles in a size range of 1 µm to 3 µm. ASHRAE 52.2 can capture this drop if the test is performed with the optional Appendix J provided by MERV-A.
To help protect against the COVID-19 virus, ASHRAE changed its recommendation from merv 8 filters to MERV 13+. Therefore, a filter with a merv rating of at least 13 would efficiently capture COVID-19 virus particles and could help reduce the spread of COVID-19 indoors. These handy devices come with multiple filters to trap harmful particles and remove a large amount of COVID particles from indoor air. MERV 16 is the tallest filter you can buy, but your air conditioning system may not be able to handle it.
A MERV 13 will trap less than 75% of air particles that are 0.3-1.0 microns in size (coronavirus is 0.1 microns). A filter with a MERV rating of 14 may remove VOC* from the air, while a different filter with the same rating may not be able to. MERV 13 and above can be used as a final filter in cleanrooms, operating rooms, inpatient hospital care, and smoking rooms. In cases where the ventilation system cannot handle a high-efficiency filter, you can use a portable air purifier while upgrading to the highest possible MERV rating with existing capacity.
To improve indoor air quality and prevent COVID-19 infections, it's best to start with an inspection by an experienced HVAC engineering company. It's important to note that MERV and HEPA are two different types of air filters, although you've probably seen both related to air filtration. In addition, Camfil is leading the charge to educate customers on different merv ratings and how to know if you're getting what you paid for. Follow ASHRAE indoor air quality recommendations to reduce aerosol transmission of Omicron.
