Minimum Efficiency Report Values, or MERV, report the ability of a filter to capture particulates. Filters with MERV-13 ratings or higher can trap smaller particles, including viruses. Many home HVAC systems will have a MERV-8 filter installed by default. What you need to know to keep you and your building safe Can building air filtration protect me from COVID-19? What filter should I use to protect those in my building from COVID-19? Why shouldn't I use the highest efficiency filter you can find? I know hospitals have a good leak, why don't we 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 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? While we're all social distancing and staying at home amid the COVID-19 pandemic, some may be wondering what else they can do to “flatten the curve”.
While hand washing and staying at home remain the most effective means of limiting the spread of the virus, conflicting information emerges about the role and effectiveness of air filters. Can air filtration in a building protect me from COVID-19? Filtration in building heating, ventilation and air conditioning (HVAC) systems may be part of an overall risk mitigation approach, but it is not generally considered a solution in itself. There is no direct scientific evidence of benefit, but reduced exposure can reasonably be inferred based on the ability of some filters to remove particles containing the SARS-CoV-2 virus. For filters to have any impact on the transmission of infectious diseases, transmission must occur through the airway, filters must be properly installed and maintained in systems suitable for treating recirculated air, and filters must be designed appropriately for the building in which they are used.
More importantly, in most buildings and in most situations, filters can be considerably less effective than other infection control measures, such as social distancing, isolation of known cases and hand washing. What filter should I use to protect people in my building from COVID-19? Hospitals (and many healthcare facilities) have specially designed mechanical systems that can be adapted to the filtration levels they need. They are often based on other control systems and strategies (for example,. The most important thing is that they have dedicated staff who operate and maintain this equipment so that it provides maximum benefit.
What about ultraviolet (UV) lamps? Do they work? What about ionizers, ozone generators, plasma and other air cleaning technologies? None of these technologies have been shown to reduce infection in real buildings, even if they show promise based on tests conducted in a laboratory or in an idealized environment. Some of them are considerably concerned about secondary issues (such as ozone production). What about portable air filters? Yes, most public health guidelines suggest that transmission of COVID-19 is predominantly associated with large droplets. This is why air filtration is only a small part of a solution, as it generally does not address transmission by surface contact or by close contact between people.
However, the distinction between airborne and droplets is particle size. We know that (a) droplets can remain in the air for long periods of time (for example,. In addition, DNA and RNA from other viruses have been found, which are usually associated with droplets in the filters used. What precautions should I take when changing filters? In general, it is advisable to assume that filters contain microbiological active material.
It is not known whether this represents a significant risk of infectious virus disease, but the precautionary principle suggests that care should be taken. This becomes particularly important in any building (including a home) where infectious diseases, including COVID-19, are known or likely, and also extends to portable air purifier filters and vehicle cabin air filters. Filters should be replaced with the system turned off, with gloves, with respiratory protection if available, outdoors if possible and disposed of in a sealed bag. Where can I go for more information?.
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. For this, CDC recommends a MERV of 13 or more. This is more than enough to block droplets and dust at least a few microns in diameter.
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 particulates than a typical MERV 8 filter. However, it is not as good at capturing small particles the size of a virus as a HEPA can. A MERV 13 will trap less than 75% of air particles that are 0.3 to 1.0 micron in size (coronavirus is 0.1 micron). It is also difficult for many existing HVAC (heating, ventilation and air conditioning) systems to adopt a MERV 13 due to the increased load on the fan by the finer filter media, which can actually cause more harm than good, as well as reduce airflow if your system is not designed to handle that type filter.
On average, many installations are limited to one type of filter MERV 8 or MERV 9.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 simply a MERV 13 considering the small size of a virus (0.06-0.12 microns); the more efficient the filter, the better. MERV 17 to 20 will also capture virus carriers, carbon dust, combustion smoke, radon progeny and microscopic allergens (particles with a size of 0.3 microns). Alternatively, you can upgrade the ventilation system itself, making it suitable for at least MERV 13 filters. HEPA filters can capture many germs in the air and also non-living pollutants such as fine particles.
Professional opinion from an HVAC engineer is strongly recommended before attempting to upgrade any air filter. Unlike other manufacturers, they also test each individual filter instead of performing batch tests, which is what other companies do. The test procedure for merv classification uses 6 measurements and 12 particle sizes, resulting in a total of 72 data points. You are more likely to find this type of filter in hospitals and laboratories, sterile environments that need advanced purification.
However, the restriction of the air flow of these filters causes a pressure drop and the capacity of the ventilation system must be considered before using them. A filter with a MERV rating of 14 may remove VOC* from air, while a different filter with the same rating may not be able to remove VOC*. . .