Coronavirus Technology Solutions
August 10, 2020
MERV 13 Can Become MERV 8 After Charge is Dissipated
Higher Efficiency Filters Needed in Schools and Commercial Buildings
Oklahoma Schools are Not Going to be Safe
Penn State Upgrading to MERV 13
Boston University Upgrading to MERV 13 but there are Concerns about Mask Efficiency
Filters and HVAC Webinar Slated for September 10
Ways to Improve Air Filtration Efficiency
McIlvaine is Forecasting Large Market for Fan Filter Units
Largest Growth will be in More Efficient Filters
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MERV 13 Can Become MERV 8 After Charge is Dissipated
Camfil has released a new video explaining MERV-13 air filters, the importance of a MERV-A rating, and advice for publicly accessible facilities.
Some manufacturers rely on an electrostatic charge to increase the efficiency of filters. As this charge dissipates over time, so does the filter’s efficiency. The ASHRAE 52.2 test standard includes an Appendix J to the standard which details a procedure to test the filters without the benefit of an electrostatic charge. The efficiency without this charge is referred to as a filter’s MERV-A value.
A good way to select the proper filter is to remember that ‘A’ stands for ‘actual’ and a food plant should always select filters based on their MERV-A value, not simply their MERV. It may seem like a small difference, but it’s not,’” says , Patrick Lally, Food and Beverage Segment Manager for Camfil USA.
“If your system has the capacity, Camfil air filtration experts recommend an air filter labeled as a MERV-15A or MERV-16A. A basic guideline would be the highest MERV-A that your infrastructure can handle,” says Greg Herman, Camfil’s National Accounts Segment Manager.
What is the Difference Between MERV-13 and MERV-13A? Recommendations and mandates have recently been citing MERV-13 air filters as a starting point for reducing infection risks in publicly accessible buildings. In the filtration industry, efficiency refers to ASHRAE’s (The American Society of Heating, Refrigerating and Air-Conditioning Engineers) national testing standards, known as MERV, or Minimum Efficiency Reporting Value. Some manufacturers rely on an electrostatic charge that temporarily increases the MERV value of their air filters. As this charge dissipates over time, so does the air filter’s MERV value.
Though it may seem like a small difference, it’s essential to know the air filter’s MERV-A value. “Many states and organizations are pushing MERV-13,” says Mark Davidson, Manager of Marketing and Technical Materials at Camfil USA, “and because they are not specifying MERV-13A, effectively speaking, many are actually getting only MERV-8 filtration.”
When it comes to stopping the spread of infection, the higher the air filter efficiency, the better. COVID-19 & Respiratory Droplets and Droplet Nuclei in Commercial & Public Buildings Respiratory droplets and droplet nuclei are two categories of droplets based on size and are expelled when people cough, sneeze, talk or even breathe. Respiratory droplets are those greater than 5 microns in size. Masks and social distancing measures are designed to prevent us from inhaling these larger droplets from infected individuals, and sanitizing measures prevent us from picking them up off of surfaces once they settle nearby.
Droplet nuclei on the other hand are much smaller and lighter, less than 5 microns in diameter, and can linger in the air for longer periods of time. They can get caught in the return of an HVAC system and recirculate into other parts of the building, meaning that they can infect a larger group of people. This is the reason for needing high-efficiency filtration in public buildings.
Higher Efficiency Filters Needed in Schools and Commercial Buildings
If one assumes that the capture of COVID on a percentage basis is equivalent to the MERV efficiency at 0.3 microns, the MERV 8 filters installed in most schools are removing only 10%. They may be capturing 75% of the 10 micron cough droplets but if these droplets evaporate then 90% of the virus in these droplets will pass through the filter.
Children wearing masks will be generating small aerosols. So even a MERV 16 filter will remove only 70% of the virus. A vaccine vial in a pharmaceutical cleanroom is protected by a 99.999 % removal of any potential virus in the air. It would therefore be a priority to do better than 70% to protect children and teachers.
As evident by Kowalski and Bahnfleth's data, the MERV rating has a significant effect across the full spectrum of particle mean diameter. Of particular interest here is for airborne microorganisms smaller than 0.3 micrometers, which includes the majority of viruses and smaller bacteria. Generally speaking, MERV 13-16 will filter over 80 percent of airborne microorganisms smaller than 0.3 micrometers.
There are many qualifiers to this data, however; as noted by Kowalski and Bahnfleth:
- "It should be noted that the variations in filter efficiency for any given MERV ratings is probably on the order of at least +/- 20 percent."
- "Most filters today use a range of filter fiber diameters, which provides considerable flexibility in matching the filter model to MERV or vendor data."
- The actual curvature for specific filters with MERV ratings exhibited in the model "can vary considerably."
- "The models presented are only generally representative of the entire array of MERV filters since considerable variation is possible by different filters with the same MERV rating."
- The curvatures, which are depicted for 500 fpm, will shift as operating velocities vary. Yet, "this filter model should provide reasonably accurate estimates of filter performance at other operating velocities."
- "Airborne microbes can be removed by filters at rates that depend on the filter performance curve and the mean diameter of the microbes."
Oklahoma Schools are Not Going to be Safe
Plans to safely reopen Oklahoma schools are plentiful, but not much can be done to improve air quality in buildings. School officials must rely on existing equipment that is not designed to filter out coronavirus particles.
Replacing heating, ventilation and air-conditioning systems to meet new guidelines for addressing COVID-19 is cost prohibitive for school districts unless patrons agree to pay for it through a bond issue. Even upgrading current systems by incorporating higher-grade filters is expensive and is not always feasible, experts agree.
“The problem is so insurmountable that people aren’t talking about it,” said state Rep. John Waldron, D-Tulsa, who taught high school for 15 years.
The state House Democratic Caucus is drawing attention to the issue by including it on a list of “needs that must be met before school can resume in the fall.” The lawmakers argue that school buildings should meet ventilation standards for COVID-19 recommended by the Centers for Disease Control and Prevention.
The CDC on July 9 published steps office building managers can take to create a safe and healthy workplace during the COVID-19 pandemic.
The guidelines are based on the standards written by the American Society of Heating, Refrigerating and Air-Conditioning Engineers. The engineers group recommends a filter with a minimum efficiency reporting value of 13 for capturing airborne viruses and states MERV 14 filters are preferred.
Filters in most homes and commercial buildings are rated 5 to 12. Guidelines for school building upgrades set by the U.S. Environmental Protection Agency call for MERV 8 filters.
“For years, we have used MERV 8 90% particulate filters,” said Susan Parks-Schlepp, public information officer for Edmond Public Schools. The district has 28 buildings ranging in age from many decades old to nearly new.
“What we are doing in units where adjustments are possible is to increase the fresh air makeup,” Parks-Schlepp said.
That follows the CDC recommendation for schools to increase the circulation of outdoor air as much as possible. If the HVAC system cannot filter or pull in outside air, the guideline suggests opening windows and doors where it does not pose a risk.
Many schools have windows that don’t open, said state Rep. Melissa Provenzano, D-Tulsa, a former teacher and administrator.
Shawnee Public Schools Superintendent April Grace said two or three teachers have decided to retire in the past couple of weeks and more families than usual have signed up for the virtual learning option. But most teachers and families want to return to in-person learning if it is safe, she said.
The HVAC systems in the district’s eight school buildings are in the range of MERV 10, Grace said. Units replaced in part of the high school are the only ones at the MERV 13 level.
Voters in the Shawnee district will be asked to approve two school bond propositions totaling $18 million on Aug. 25. About $4 million would go to HVAC system replacements and upgrades, Grace said.
Tulsa school district will spend $ 300,000 to bring in more outside air.
Penn State Upgrading to MERV 13
Penn State has more than 2,000 buildings across all campuses, there are numerous other efforts underway to help prevent COVID-19 from spreading on campus. The University has purchased 6,000 hand sanitizer stations, with up to 3000 of them to be installed at University Park, 1200 being deployed to the campuses, and the remainders to be available for purchase by units. Hands-free faucets are being installed in some of the most high-traffic areas on campus, and Plexiglass sneeze guards, while limited in application, will also be installed where appropriate.
The university is in the process of upgrading the air conditioning filters from ones with a Minimum Efficiency Reporting Value (MERV) 8 rating to ones with a MERV 13 rating. They also have changed the mechanical systems in many buildings on campuses to use more outside air, instead of recirculated inside air, to improve ventilation.
Boston University Upgrading to MERV 13 but there are Concerns about Mask Efficiency
BU Facilities Management and Operations Staff is working to improve mechanical heating, ventilation and air-conditioning systems in the 120 buildings on campus that have them.
A report released July 28 states that improvements to these buildings include replacing current Minimum Efficiency Reporting Value 8 air filters, which capture larger particles such as dust and pollen, with MERV 13 filters that are able to capture smaller contaminants, including airborne viruses like SARS-CoV-2.
For the other 198 buildings on campus without mechanical ventilation, BU spokesperson Colin Riley said that BU Facilities will be following U.S. Centers for Disease Control and Prevention guidelines by recommending windows and doors stay open when possible. BU Facilities is also recommending the installation of portable air purifiers in some spaces to increase air exchange rates.
In a message that circulated within the College of Arts and Sciences and was forwarded to The Daily Free Press anonymously, one faculty member wrote the University’s attempt to manage the situation is unrealistic.
“BU’s complex technical claims about sophisticated measures to fix HVAC classroom vulnerability do little to address concerns about the health and safety of the larger BU community,” the professor wrote. “Good luck opening the windows in our third floor seminar room or controlling circulation of air and of aerosols in CAS.”
Nathan Phillips, a professor in BU’s Department of Earth and Environment, said that while BU’s planned ventilation improvements are a step in the right direction, he is still concerned about teaching indoors because of the University’s mask policy, which currently requires students and faculty to purchase their own masks that meet basic criteria.
“The mask and ventilation issues are linked in a way that is not being fully understood right now,” Phillips said. “Where is the most important filter that no one’s talking about? I mean for airborne transmissions, it’s the masks that we have on our faces.”
Phillips said he does not think BU’s mask criteria will cut it when it comes to safety from airborne transmission.
“We’ve got to do better than just saying, ‘do-it-yourself face coverings,’” Phillips said, “because if students or faculty or instructors, whoever, show up in bandanas, that is not going to be sufficient based on what we know.”
Filters and HVAC Webinar Slated for September 10
The next Filters and HVAC webinar is scheduled for 10:00 AM CDT September 10, 2020. To register Click here
This webinar will continue the analysis created in previous webinars.
This webinar will be a high level discussion and debate relative to the issues affecting filter or treatment type, efficiency, air quantity, and direction. It will expand on the previous webinars and interviews which you can see below. It will also reference the articles in the Alerts. Even if you are not a subscriber you can see the titles Search All Alerts by Keyword.
We just added to the issues which will be discussed along with any others volunteered by participants. Here is the expanded list of air filter issues to be discussed on September 10.
|
Issue |
Aspects |
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Virus Parameters |
Size, quantity, minimum infectious load, life, destruction methods, deposition on duct internal surface, distance traveled |
|
Treatment Types |
Filtration, ionization, UV disinfection, precipitators, carbon beds. What is the performance and how widely is each used? Are combinations used and is this a benefit? |
|
Filter Design |
Pleated, panel, box, pocket |
|
Filter Media |
Membranes vs micro fiberglass for high efficiency, shapes, pleats, and other parameters |
|
Particulate Efficiency |
Viral removal performance of the range of MERV and HEPA filters including the efficiency after any electrostatic charge dissipates |
|
Placement |
Pre filter or final filter, |
|
Pressure Loss |
Filter depth vs filter efficiency and pressure drop |
|
Filter Inventory |
How efficient are filters now installed in schools, nursing homes, meat processors, etc. What about buildings without HVAC? |
|
Expense |
How costly will it be to install more efficient filters? |
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Air Quantity |
How many air changes per hour are needed? How much outside air should be introduced? How is this limited cost wise by outdoor temperature and humidity? |
|
Air Direction |
How is air directed so that the maximum amount flows from transmitter to the HVAC system and then is diluted prior to reaching the recipient? Where are partitions and diffusers beneficial? |
|
Room Air Purifiers |
When and where should they be used and what volume and efficiency is needed? |
|
Fan Filter Units |
Where should they be used rather than partitions or in conjunction with partitions? |
|
Isolators, Modules |
Where are isolators and modular cleanrooms the best choice? |
|
Pollution Combination |
Use of filters to eliminate air pollutants and viruses in outdoor spaces such as traffic intersections? |
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Indoor Air |
Benefits of purifying indoor air to remove pollutants as well as viruses; a common metric to measure all harm and good |
|
Processes |
Rooms, elevators, reception, cashier counters, industrial processing, machinery rooms, individual AC units |
|
Facilities |
Residential, commercial, hotel, nursing homes, hospitals, dental, meat processing, schools, gyms, transportation |
Ways to Improve Air Filtration Efficiency
There is a need for lower pressure drop media with higher efficiencies to battle COVID. Here are articles in the Alert from July 1 until August 7.
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Recent Filter Media Analyses in the Coronavirus Technology Solutions |
|||
|
Date |
Company |
Type |
Details |
|
8-7 |
Verder |
Nanofiber |
Surface and depth |
|
8-7 |
HiFyber |
Nanofiber |
High efficiency |
|
8-7 |
Fibertex |
Nanofiber |
High and medium efficiency |
|
7-27 |
AAF |
Fiberglass |
MERV 16 |
|
7-24 |
H&V |
Nanoweb |
MERV 15 |
|
7-24 |
Camfil |
Microfiber glass |
Single stage (no prefilter) |
|
7-24 |
Filtration Group |
Rigid cell |
Upgrade to M15 at same pressure |
|
7-22 |
Koch |
V Bank |
High virus capture with MERV 15 |
|
7-20 |
ITT |
2 inch M 13 |
Good performance on virus |
|
7-9 |
U. Houston |
Nickel foam |
Heated filter has 99.9% virus kill |
|
7-8 |
M+H |
Cabin air |
polyphenol anti-microbial coating |
|
7-1 |
AAF |
Membrane |
Better for ULPA and HEPA |
Mcilvaine is Forecasting Large Market for Fan Filter Units
Room air purifiers, fan filter units, and laminar flow systems will be critical to preventing the spread of COVID. There is already a market for small air purifiers but growth in larger units will be the trend in the future.
There will be high growth for fan-filter units which will be a better solution than partitions. The best solution is controlled laminar air flow systems with HEPA filtered air. They will find increasing use in nursing homes, meat processors and other applications in addition to their present use in cleanrooms and hospital operating suites. McIlvaine is forecasting each of these products for every application in each country.
Largest Growth will be in More Efficient Filters
Evidence is growing that highly efficient air filters will be needed to vanquish COVID. A proactive program by filter and media suppliers would greatly reduce COVID and generate very large revenues for suppliers of media and filters.
MERV 8 filters will not remove more than 15% of the viruses. MERV 13 filters will remove about 40% of the viruses. The MERV 16 filter will remove close to 70%. The market for high efficiency MERV 17-20 filters with a proactive supplier program is forecast to grow 10 fold over the next 4 years. While the MERV 14-16 market will grow 7 fold according to the latest McIlvaine forecast.
