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.
Ultraviolet (UV) systems are a great way to maintain 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 surface disinfection benefits. 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.
Mobile UV systems are also 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 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 the recommendation of a Merv 13 or higher, does a MERV 13 filter meet your needs? A MERV 13 filter is a step in the right direction and captures more particles than a typical MERV 8 filter. However, it's not as good at capturing small virus-sized particles as a HEPA can. 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). It is also difficult for many existing HVAC (HVAC) systems to adopt a MERV 13 because of the greater fan load of finer filter media, which can actually cause more harm than good and reduce airflow if your system is not designed to handle that type of filter. Considering the threat posed by the spread of COVID-19 and other germs, upgrading a building's air filter to a HEPA is a much more effective step than just a MERV 13 considering the small size of a virus (0.06-0.12 microns); the more efficient the filter, the better.
MERV 13 and above can be used as a final filter in cleanrooms, operating rooms, inpatient hospital care, and smoking rooms. MERV 14 and higher can capture particles that are even smaller than previous MERV ratings, ranging from 0.3 to 1.0 microns in size. With increased air filtration provided by higher MERV ratings, there will also be a pressure drop, which will reduce airflow through the system and therefore more energy expenditure to keep up with fan resistance. 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.
With a portable air purifier through Sanalife, you can access easy-to-use air filtration systems with MERV 13+ ratings. Good MERV sorting efficiency will improve indoor air quality and reduce the spread of virus particles. One of their recommendations is to use air cleaners with at least a MERV 13 rating, or a higher HEPA rating when possible. A HEPA filter is essentially the ultimate solution in the air filter world and far exceeds what a MERV 13 can do.
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. 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. Filters with a MERV rating of 11 can capture some coronavirus particles (65%), but MERV 13 are more effective, removing 85% of particles at 0.3 microns. Considering all these factors it's clear that Merv 13 filters are good enough for fighting Covid-19 but they should be combined with other measures such as portable air purifiers or HEPA filters for maximum effectiveness.
