Here are some examples: In non-residential settings, consider running the HVAC system at maximum outside airflow for 2 hours before and after the building is occupied. Select from 1", 2', and 4" depths. He added that on days when the UV lights were deployed in hospitals, "the air was about 80 percent less infectious.". One way to do this for room air cleaners is to select a HEPA fan system with a Clean Air Delivery Rate (CADR) [See EPA’s Guide To Air Cleaners In The Homepdf iconexternal icon] that meets or exceeds the square footage of the room in which it will be used. And he said we should "absolutely" look at the MERV 13 filters for our homes. MERV filters have a rating system… MERV 7, 8, 10, and so on—up to MERV 20. Increase airflow to occupied spaces when possible. Removal times will be longer in rooms or areas with imperfect mixing or air stagnation.” Appropriate use of Table B.1 to establish clearance times from any space requires multiplying the time in the table by a mixing factor (k) that ranges between 1 and 10. Now, he says if you increase the efficiency, your fan has to do to more. Depending on the size of the HEPA fan/filter units and how the facility in which they are being used is configured, multiple small portable HEPA units deployed to high risk areas may be more useful than one large HEPA unit serving a combined space. Our filters are available in three grades – Merv 8, Merv 11, and Merv 13. MERV values range from 1 to 16 and higher MERV values correspond to more efficient filters. So you need to … Turn off any demand-controlled ventilation (DCV) controls that reduce air supply based on occupancy or temperature during occupied hours. How much time is required to reduce the airborne particle concentration by 99 percent? Examples of “less-clean” spaces might include spaces that contain known/suspect infectious persons or spaces where a known activity has increased likelihood of generating infectious airborne particles. A True HEPA filter will certainly capture some COVID-19 particles. While cleaning your air is important for any in-person business, it should not be … It will be up to the building owner/operator (obtaining expert consultation as needed) to identify which tools are appropriate for each building throughout the year. Learn more about indoor air in homes and Coronavirus (COVID-19). MERV filters with a minimum rating of 8 to 12 are ideal for filtering out pollen and mold spores. Creation of the directional airflow can also be done actively, through the use of fans exhausting through open windows, strategic placement of ductwork attached to portable HEPA filtration units, or dedicated exhaust systems (installed or portable) that generate a desired airflow by exhausting air out of windows, doorways, or through temporary ducts. Nardell, who's been a specialist in tuberculosis since the early '80s, worked with TB patients in American homeless shelters. Scientific developments in filter design have reduced the amount of the increased pressure drop and its resulting impact on HVAC operations, but not all filters have adopted the newer technology. Was the technology evaluated for potential adverse health effects or occupational exposures? While MERV ratings reflect a filter's ability to trap both microscopic and macroscopic particles, MPR ratings only grade a filter on its capacity to remove particles from 0.3 to 1 microns. Testing of the directional airflow effectiveness can be accomplished using visual tracer techniques that use “smoke tubes” or handheld “fog generators.” Other tools, such electronic monitors or visual aids to monitor pressure differences can be used when directional airflow is established between two adjacent spaces. It has an average size of 0.12 microns. For reference, a typical dust particle is between .2 and 8 microns, while pollen starts at … The addition of the HEPA filter device provides additional clean air to the room. The company also offers a more robust purifier intended for use in medical spaces. When indoors, ventilation mitigation strategies help to offset the absence of natural wind and reduce the concentration of viral particles in the indoor air. Second, if faced with a MERV-13 regulatory mandate and budgetary concerns that prevent the first choice, then 2-inch MERV-13 (not MERV-13A) air filters could be sourced, but be aware that the actual performance of MERV 13 air filters will be closer to MERV-8 after a period of time. Filters like a MERV 13 get you closer to 80 or 90 percent, or HEPA filters capture 99.97 percent of particles, so upgraded filters … According to ASHRAE most modern HVAC systems can function properly with an air filter rated as MERV 13, especially for systems with a 2" or 4" thick filter. A: A MERV 16 rated filter is 95% or better efficiency for particles of 0.3 to 1.0 micron sizes. MERV filters are not effective at filtering microbes and viruses until they are rated at 17 or better. Increased ACH generally leads to reductions in k, although k can also be reduced by the use of a fan in the space, which does not have an impact on ACH. Below is a list of ventilation interventions that can help reduce the concentration of virus particles in the air, such as SARS-CoV-2. Using the mixing factor of 3, the estimated wait time for 99% reduction of airborne contaminants in the room is 3 x 23 = 69 minutes. While MERV ratings reflect a filter's ability to trap both microscopic and macroscopic particles, MPR ratings only grade a filter on its capacity to remove particles from 0.3 to 1 microns. Of all the unknowns still surrounding the transmission of the coronavirus, one thing is for sure: Being indoors with lots of people in cramped conditions is a major no-no. However, the virus generally does not travel through the air by itself. Increase outdoor air ventilation, using caution in highly polluted areas. Because not every HVAC system is compatible with the HEPA filter, you might need to retrofit your HVAC system, which involves optimizing existing HVAC networks for new components. However, the virus generally does not travel through the air by itself. Ducted HEPA systems can also be used to establish direct source capture interventions for patient treatment and /or testing scenarios (See CDC/NIOSH discussion on Ventilated Headboard). There is mounting evidence that MERV 13 rated HVAC air filters reduce and remove these droplets and particles. The higher the MERV rating on a filter, the fewer dust particles and other contaminants that can pass through it. Thus, they give effective air exchanges without the need for conditioning outdoor air. By definition, a High Efficiency Particulate Air (HEPA) filter is at least 99.97% efficient at capturing particles 0.3 µm in size. Here’s what we tell them: Think of MERV 8 filters as a “good” option, and MERV 11 filters as the “better” option for normal residential use. What Merv rating should I use? HEPA fan systems can be used as stand-alone units, or many larger units allow flexible ductwork to be attached to the air inlet and/or outlet (note that larger ducted units don’t fall under the “room air cleaner” description and may not have a CADR rating). The added air movement within the room improves overall mixing, so assign k = 3. When used along with other best practices recommended by CDC and others, filtration can be part of a plan to protect people indoors. The risk of spreading the virus that causes coronavirus disease 2019 (COVID-19) through ventilation systems is not well-known at this time. One research group reported that the use of a new air-sampling method allowed them to find viable viral particles within a COVID-19 patient’s hospital roomexternal iconexternal icon with good ventilation, filtration and ultraviolet (UV) disinfection (at distances as far as 16 feet from the patient). To help protect against COVID-19 virus, ASHRAE changed its recommendation from MERV 8 filters to MERV 13+. The scale ranges from 1-16, with 16 being the most effective. Increasing filtration efficiency can increase the pressure drop across the filters. What kind of filter should I use in my home HVAC system to help protect my family from COVID-19? Directional Airflow is a protective ventilation concept where air movement flows in a clean-to-less-clean direction. Thus, HEPA filters are no less than 99.97% efficient at capturing human-generated viral particles associated with SARS-CoV-2. It has been floating around for years. The creation of directional airflow can be accomplished within a particular space or between two adjacent spaces. Considering the sensitivity surrounding Covid-19, HEPA filters might be ideal. But a MERV 8 filter is not fine enough to take out PM2.5 or viruses; for that, you need at least MERV … There may be some implications for HVAC systems associated with these findings, but it is too early to conclude that with certainty. Although there are some highly contagious airborne diseases (like measles) where CDC provides specific guidance for 99.9% clearance wait times, the general recommendation in CDC’s Guidelines for Environmental Infection Control in Health-Care Facilities is to wait to allow for a 99% reduction of any generated airborne particles before re-entering the room. The lower the concentration, the less likely some of those viral particles can be inhaled into your lungs; contact your eyes, nose, and mouth; or fall out of the air to accumulate on surfaces. It is definitely not a new idea. The specific combination of tools chosen for use at any point in time can change. What filter should I use to protect those in my building from COVID-19? Filter Selection Flowchart COVID-19 Risks for Indoor Air This will help draw fresh air into room via other open windows and doors without generating strong room air currents. Dilution ventilation and particle filtration are commonly used to remove these smaller particles from the air. Retrofitting an HVAC system might also supply energy savings, as resealing or replacing ductwork, for instance, can curb energy waste. SARS-CoV-2 viral particles spread between people more readily indoors than outdoors. Our advanced pleat technology provides less air flow resistance, with higher efficiency. No, it can’t. What MERV filter is recommended for preventing the transmission of airborne illnesses such as COVID-19? When weather conditions allow, increase fresh outdoor air by opening windows and doors. Healthcare facilities have ventilation requirements in place to help prevent and control infectious diseases that are associated with healthcare environments. Our Merv 8 filter eliminates allergens such as dust, pollen, mold spores, and pet dander. See Example 2 for more information, including an example of the calculations. It can take several minutes for particles 10 µm in size to settle, while particles 5 µm and smaller may not settle for hours or even days. Here are four steps for improving your company's air quality and more. it is uncontaminated supply air or it is the clean exhaust from a High Efficiency Particulate Air (HEPA) fan/filtration system [See HEPA filtration discussion below]). However, the concentration of viable virus detected was believed to be too low to cause disease transmission. However, GUV can inactivate viruses in the air and on surfaces*. This includes using multiple mitigation strategies with several layers of safeguards to reduce the spread of disease and lower the risk of exposure. CDC recommends using the highest efficiency ventilation filters possible, without having detrimental effects on overall HVAC system performance. "Filtration or air cleaning is not magic," says Siegel. Do not open windows and doors if doing so poses a safety or health risk (e.g., risk of falling, triggering asthma symptoms) to occupants in the building. To safely achieve this, fan placement is important and will vary based on room configuration. How much time is saved to achieve the same 99% reduction in airborne contaminants by adding the portable HEPA device to the room? Directional airflows must be evaluated carefully. There are numerous devices being heavily marketed to provide air cleaning during the ongoing COVID-19 pandemic. The performance is based on particles that are 0.3-10 micron in diameter. This can be done passively, through intentional placement of supply and exhaust heating, ventilation, and air conditioning (HVAC) grills or by the intentional creation of pressure differentials between adjacent spaces through specification of offset exhaust and supply air flow rates. Some devices even include both technologies. A MERV 8 air filter is efficient at trapping a majority of indoor particulates that could debilitate those with asthma and allergies, or even cause long-term respiratory problems. But a MERV 8 filter is not fine enough to take out PM2.5 or viruses; for that, you need at least MERV … Now, calculate the air changes per hour: ACH = [Q x 60] / (room volume) = (72 cfm x 60) / (12’ x 10’ x 9’) = 4320/1080 = 4.0 ACH. Some of the most common are ionization and/or dry hydrogen peroxide devices. In homes and buildings where the HVAC fan operation can be controlled at the thermostat, set the fan to the “on” position instead of “auto,” which will operate the fan continuously, even when heating or air-conditioning is not required. Using Table B.1, the perfect mixing wait time based on 12 ACH and a 99% reduction of airborne particles is 23 minutes. They represent a list of “tools in the mitigation toolbox,” each of which can be effective on their own. However, this may be difficult to do in cold, hot, or humid weather. Examples of “clean” spaces might include healthcare facility triage stations or rooms/corridors adjacent to higher risk activities. For reference, a typical dust particle is between .2 and 8 microns, while pollen starts at … Obtain consultation from experienced Heating, Ventilation and Air Conditioning (HVAC) professionals when considering changes to HVAC systems and equipment. The cost of retrofitting an HVAC system to a MERV 13 filter depends on the size and age of your current system, with smaller jobs clocking in at 25 cents per cubic foot per minute, says Gabriel Domenikos, director of operations at Airlogix, a commercial and industrial air conditioning and refrigeration company based in New York City. Use fans to increase the effectiveness of open windows. Germicidal Ultraviolet (GUV), or Ultraviolet Germicidal Irradiation (UVGI), is a disinfection tool used in many different settings, such as residential, commercial, educational, and healthcare. This does not necessarily imply the technologies do not work as advertised. 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. Most home furnace filters have a MERV Rating around 8, which will take out pollen and dust. Since the COVID-19 pandemic hit North America last February, building IAQ has come into an entirely different focus. Cognizant authorities such as the CDC and ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers) recommend an air filter with a minimum rating of MERV 13. Since Qe is larger than Qs by 7 cfm, the heating, ventilation, and air conditioning (HVAC) system is pulling 7 cfm of air into the room from adjacent areas (i.e., the room is under negative pressure). This can lead to increased fan energy, reduced airflow rates, and/or issues controlling indoor temperature and relative humidity levels. Accordin… Regardless of whether the 99% or 99.9% column on Table B.1 is used, the value in the table is usually an under-estimation of the actual dilution clearance time as noted in the table’s footnotes which include the following statement: “The times given assume perfect mixing of the air within the space (i.e., mixing factor = 1). The larger the CADR, the faster it will clean the room air. HEPA is a type of pleated mechanical air filter. Cost estimates per room for the listed ventilation interventions in cost. Inspect and maintain local exhaust ventilation in areas such as kitchens, cooking areas, etc. Ensuring appropriate outdoor air and ventilation rates is a practical step building owners and managers can take to ensure good indoor air quality. What is the particle size of the COVID-19 virus? A PECO filter mightmake a difference, but only in a limited way. Both can improve a room's air quality, but HEPA filters are denser, making them ideal for labs or hospitals, where people often handle dangerous materials. Operate these systems any time these spaces are occupied. Now, he says if you increase the efficiency, your fan has to do to more. Using ductwork and placing the HEPA system strategically in the space can help provide desired clean-to-less-clean airflow patterns where needed. What is a Merv rating? So do have a local HVAC contractor weigh in your options, adds Hager. Did the study environments represent your environment and intended use? Our Merv 8 standard capacity pleated filters are offered in ASHRAE 52.1 and 52.2 (MERV) ratings and are built to withstand rigorous conditions. Thus, the recommended filters are significantly more efficient at capturing particles of concern than a typical MERV 8 filter, which is only around 20% efficient in the 1 µm to 3 µm size range and is not rated for capture efficiency of the smaller 0.3 µm to 1.0 µm particles. Can ventilation filters effectively capture SARS-CoV-2 viral particles? 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. Does germicidal ultraviolet (GUV) disinfection kill the virus that causes COVID-19? When outdoors, the concentration of viral particles rapidly reduces with the wind, even a very light wind. Ensure restroom exhaust fans are functional and operating at full capacity when the building is occupied. Because our intention was to focus this study on high-efficiency HVAC filters, i.e., MERV 12 and higher, we selected MERV 12, MERV 13 and MERV 14 fil-ters because these high-efficiency filters are commonly used in homes. By themselves, portable air cleaners and HVAC filters are not enough to protect people from the virus that causes COVID-19. This factor represents how well the ventilation system mixes and dilutes the concentration of airborne particles within the room. Thus, the recommended filters are significantly more efficient at capturing particles of concern than a typical MERV 8 filter, which is only around 20% efficient in the 1 µm to 3 µm size range and is not rated for capture efficiency of the smaller 0.3 µm to 1.0 µm particles. While large droplets (100 micrometers [µm] and larger) will settle to surrounding surfaces within seconds, smaller particles can stay suspended in the air for much longer. The MERV provides a measure of the “filter efficiency” over the range of particle sizes prescribed in the test procedure. If a MERV 13 filter is not a viable option in the HVAC system, then use the highest MERV rating you can. If the room in which the air cleaner will be used is taller than 8 feet, choose an air cleaner with a proportionally higher CADR than that based simply on square footage. It is suggested to have the fan run continuously and change filters every 30 days. HEPA filters are even more efficient at capturing particles larger and smaller than the MPPS. In choosing a portable HEPA unit, you want to select a system that is appropriately sized for the area in which it is installed. Implementing multiple tools at the same time is consistent with CDC mitigation strategies and increases overall effectiveness. Unsubstantiated claims of performance or limited case studies with only one device in one room and no reference controls should be questioned. Filters for use in heating, ventilation, and air conditioning (HVAC) systems are generally tested under procedures outlined in ANSI/ASHRAE Standard 52.2-2017-Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size. For more information, see the CDC Guidelines for Environmental Infection Control in Health-Care Facilities. We focused on filters in the MERV 8 to 13 range because they are good to excellent at removing fine particulates (as small as 0.3 to 3.0 microns in … These viral particles are human-generated, so the virus is trapped in respiratory droplets and droplet nuclei (dried respiratory droplets) that are larger. Using the mixing factor of 5, the estimated wait time for 99% reduction of airborne contaminants in the room is 5 x 69 = 345 minutes or 5 hours and 45 minutes. Here, the clean volumetric air flow rate (Q) is:  Q = Qe + Qhepa = 72 cfm + 145 cfm = 217 cfm. Be sure to seek consultation with a reputable GUV manufacturer or an experienced GUV system designer prior to installing GUV systems. It starts with getting a good air filter. CDC recommends a layered strategy to reduce exposures to SARS-CoV-2, the virus that causes COVID-19. Using Table B.1 the perfect mixing wait time based on 4 ACH and a 99% reduction of airborne particles is 69 minutes. For HVAC systems suspected to be contaminated with SARS-CoV-2, it is not necessary to suspend HVAC system maintenance, including filter changes, but additional safety precautions are warranted. In mild weather, this will not affect thermal comfort or humidity. The Centers for Disease Control and Prevention (CDC) cannot attest to the accuracy of a non-federal website. In other words, a job that takes one hour--which Domenikos says is the standard amount of time it takes to retrofit a single HVAC unit--could cost around $2,000 for a typical 4,000 square-foot office space in New York or upwards of $25,000 for a 100,000 square-foot space. As a rule of thumb, rooms with higher airflow rates (6 ACH and higher) and good placement of supply and exhaust grilles (hospital airborne infection isolation rooms) are considered to have “good” mixing and thus a mixing factor of k = 3 is often used for these spaces. The technology uses ultraviolet (UV) energy to inactivate (kill) microorganisms, including viruses, when designed and installed correctly. While airflows within a particular space may help spread disease among people in that space, there is no evidence to date that viable virus has been transmitted through an HVAC system to result in disease transmission to people in other spaces served by the same system. What is meant by “directional airflow?” How and where should we use it? Have performance results been published in a scientific or medical journal? • Keep systems running longer hours, if possible 24/7, to enhance the two actions above. In the absence of specific guidance specifying a longer wait period for the virus that causes COVID-19, SARS-CoV-2, the wait time associated with 99% clearance is appropriate for healthcare and other spaces. A lower density but still powerful MERV filter could be a good alternative. Mark Marston slides a MERV 13 air filter into the HVAC system outside Basics Fitness Center in Portland, Maine, on July 21. High-efficiency particulate air (HEPA) filters are even more efficient at filtering human-generated infectious particles than MERV 16 filters. Through his research, he found that UV was "quite safe." Consider portable high-efficiency particulate air (HEPA) fan/filtration systems to help enhance air cleaning (especially in higher risk areas such as a nurse’s office or areas frequently inhabited by persons with higher likelihood of COVID-19 and/or increased risk of getting COVID-19). So you need to … Standard 52.2 establishes a testing protocol. However, in the era of Covid-19, it is time to take all of the tools out of the toolbox. This type of air filter can theoretically remove at least 99.97% of dust, pollen, mold, bacteria, and any airborne particles with a size of 0.3 microns (µm). HEPA and MERV filters are usually not the same. Preferably, the documented performance data under as-used conditions should be available from multiple sources, some of which should be independent, third party sources. Thus, conservative estimates of k are often used (as described above). [See the question on Portable HEPA Filtration to learn more about them and their application in protective air cleaning]. Most commercial and residential HVAC systems have a MERV 6 or 8 filter, which takes care of the basic pollen, dust, dust mites, mold and bacteria. Example 2:  The room described in Example 1 is now augmented with a portable HEPA air cleaning device with a CADR of 145 cfm (Qhepa = 145 cfm). There is no obvious answer to this question given unknowns about the nature of SARS-CoV-2 containing particles and droplets. Saving Lives, Protecting People. Most home furnace filters have a MERV Rating around 8, which will take out pollen and dust. While the list of tools is intended to be universally applicable across indoor environments, applying them to different building types, occupancies, and activities under environmental and seasonal changes can be challenging. Clean air is essential for a safe return to the office. From retrofitting HVAC systems with mechanical filters to purifying the air with UV rays, the business of cleansing the air is big--and for the companies navigating the process, daunting. ASHRAE, has similar guidance, however, they recommend a minimum filtration efficiency target of MERV 13, provided there are not substantial negative impacts on the HVAC system performance and occupant comfort. This Standard is what led to the creation of the minimum efficiency reporting value, or MERV. Many new air disinfection devices are being marketed for their ability to inactivate the virus that causes COVID-19. A MERV 8 air filter is efficient at trapping a majority of indoor particulates that could debilitate those with asthma and allergies, or even cause long-term respiratory problems. The COVID-19 Virus is 2.5 times smaller than the 0.3 micron cutoff. Edward Nardell, a professor of global health and social medicine at Harvard Medical School, advocates using UV light to keep the air clean. However, in the era of Covid-19, it is time to take all of the tools out of the toolbox. The filter's density can be problematic, however. It is a method of stating the filter’s efficiency based on particle size and is determined by testing filter performance when exposed to particles of a known size in the air stream. The room has average air mixing, so assign k = 5. Many MERV 13 rated filters (note: non-A-rated filters) use an electrostatic charge to improve the efficiency of the air filter without having to use larger amounts of filtering material. Table B.1 in the CDC’s Guidelines for Environmental Infection Control in Health-Care Facilities (2003) provides estimates of the time required to remove airborne contaminants, including airborne viral particles, from the air through ventilation dilution, exhaust and filtration. Research has shown that the particle size of the COVID-19 virus is around 0.1 µm (micrometer). Another factor driving the popularity of MERV 8 filters is that they are inexpensive and easily serviced. A True HEPA filter captures 99.97% of all particles to a size of 0.3 microns. A MERV 5 filter was selected as a com-parative filter. Other settings that could benefit from portable HEPA filtration can be identified using typical risk assessment parameters, such as community incidence rates, facemask compliance expectations and room occupant density. Decrease occupancy in areas where outdoor ventilation cannot be increased. This 0.3 µm particle approximates the most penetrating particle size (MPPS) through the filter. One helpful strategy is to use a window fan, placed safely and securely in a window, to exhaust room air to the outdoors. This ventilation concept is applied to areas where the “clean” environment requires a higher level of protection and/or where the “less-clean” environment has a higher risk of containing airborne contaminants (activities or occupancy by individuals with a higher risk of being infectious). ACH = [Q x 60] / (room volume) = (217 cfm x 60) / (12’ x 10’ x 9’) = 13,020/1080 = 12.06 ACH (round down to 12). CDC does not provide recommendations for, or against, any manufacturer or product. Not only are consumers not interested in convening inside right now, employees are also reluctant to return to work. Note:  Determining the true value of the mixing factor is difficult and requires special equipment to measure air flows and conduct tracer gas decay testing. Minimum Efficiency Reporting Values, or MERV, reports a filter's ability to capture particles. Clear The Air Merv 8 Pleated Filters are available in 1”, 2” and 4” depth. While these systems do not bring in outdoor dilution air, they are very effective at cleaning air within spaces to reduce the concentration of airborne particulates, including SARS-CoV-2 viral particles. UV air purifiers use UV light to disinfect the air by breaking down bacteria caught in the filter. The Covid-19 diameter is around 0.1 micron. While an HVAC system handles a building's heating, cooling, and ventilation, the system's filter can be limited in terms of air purification; it might catch big particles but not smaller air pollutants. However, the virus does not travel through the air … The table provides estimates of the time required for airborne-contaminant removal based upon the room’s ventilation rate, measured in air changes per hour (ACH) and the desired removal efficiency (99% or 99.9%). Device can remove substantial amounts of particles from the air … HEPA and MERV 16 filter! 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Human-Generated viral particles associated with healthcare environments healthcare environments if you increase efficiency! And schools ) building owners and managers can take to dilute the concentration of virus safeguards have been added commercial... Obvious answer to this question given unknowns about the nature of SARS-CoV-2, the faster it will clean room... Patterns where needed viruses particles, including systems found in most homes is based on 12 ACH a.