Indoor Air Quality Solutions Blog

"Healthier Air Starts Here" (407) 383-9459




Indoor Air Quality IAQ Blog





What Are MERV Ratings and How Do They Work?


What is the Minimum Efficiency Reporting Value?
 
The Minimum Efficiency Reporting Value, also known simply as MERV, measures the performance of air purifiers, specifically large purifiers intended to clean an entire house or building. Large, whole-house purifiers are not evaluated in the same manner used to measure the effectiveness of small, portable air cleaners, which are sometimes given Clean Air Delivery Ratings (CADR) instead.
 
Whole house and building air purifiers usually receive MERV ratings of between 1 and 16, though the upper limit is sometimes extended to 20. Common residential air purification systems tend to fall within a narrower range. Higher numbers translate to more effective air filtration. According to the online encyclopedia Wikipedia, "The scale is designed to represent the worst case performance of a filter when dealing with particles in the range of 0.3 to 10 micrometers."

MERV Rating Chart



Who Uses MERV Ratings?

 
The MERV rating system was initially created by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (or ASHRAE for short) in 1987. However, this evaluation system was based on older methods that date back to 1968, when ASHRAE issued "Standard 52," the first formal testing standard for filters. According to an article by engineer Donald Newell, the purpose of the Standard has not changed since its early days, and is designed to determine the following attributes of air filters:
 • Particle removal capability
 • Resistance to airflow
 • Expected operating life
 
MERV ratings measure only the first quality, however. The MERV rating of an air cleaner is determined according to updated standards set by the ANSI/ASHRAE Standard 52.2-1999.
 
How is an Air Cleaner's MERV Rating Determined?
 
Air cleaners are given MERV ratings based on the results of a series of tests. Simply put, the process works as follows:

1. Test particles are introduced into the air of the testing area. These particles fall into one of twelve categories, based on size. The smallest category contains particles ranging from .3 to .4 micrometers (also known as "microns"). The largest includes particles from 7 to 10 micrometers.

2. The air is then passed through the filter being tested. The density of particles in the air is measured before and after the air passes through the filter to determine how effective the filter is at removing pollutants in each size category.
 
After this is done, the process is repeated five more times, so that there are ultimately six measurements for each of the twelve categories. The MERV number is assigned based on the worst result. Hence the "minimum" in "Minimum Efficiency Reporting Value."
 
What Does an Air Cleaner's MERV Rating Mean for You?
 
A helpful chart detailing what MERV ratings mean can be found at http://www.mechreps.com/PDF/Merv_Rating_Chart.pdf. Of particular interest is the column detailing what types of pollutants are filtered out at each level.
 
Precise technical details will be less important to the average customer than an answer to the question, "What MERV ratings are acceptable for my home?" The United States Environmental Protection Agency provides some information on this matter. "Medium efficiency filters with a MERV of 5 to 13," it states, "are reasonably efficient at removing small to large airborne particles. Filters with a MERV between 7 and 13 are likely to be nearly as effective as true HEPA filters at controlling most airborne indoor particles." Furthermore, the EPA adds that "medium efficiency air filters are generally less expensive than HEPA filters, and allow quieter HVAC fan operation and higher airflow rates than HEPA filters since they have less airflow resistance."
 
HEPA (High Efficiency Particulate Air) filters are the top-of-the-line air filters. Most homes are not capable of having whole-house HEPA filtration systems installed without extensive modification. Therefore, the EPA's recommendation of filters with a MERV rating from 7 to 13 is something that potential customers should keep in mind.
 
The National Air Filtration Association gives a roughly similar answer. The highest range it recommends for residential systems is 9-12; higher numbers are said to be suited for hospitals or commercial buildings rather than homes.
 
Limitations of the MERV Rating System
 
An air cleaner's MERV rating is based on its ability to filter out undesirable particles from the air. Not all indoor air pollution is particle-based, however. Gasses contribute significantly to pollution as well. The ability of an air purifier to remove particles is not predicative of its ability to remove gasses, so the MERV rating is not helpful in this regard.
 
Newell's article cautions that air filters given the ASHRAE test "are likely to perform worse than predicted because of various installation conditions." This is known as the "installation effect." Therefore, it is important to remember that MERV ratings are assigned based on a purifier's performance in carefully controlled testing conditions, and not the "real world."
 
And finally, as stated above, MERV ratings are only relevant to large air cleaners intended to affect whole buildings. Common small portable air cleaners do not have MERV ratings.
 
Conclusion
 
The MERV rating system is a helpful way to describe the capabilities of different large air cleaners. It is determined through rigorous testing and is gives the worst-case performance of the filter, so the MERV number is not inflated. No one should forget to consider MERV ratings when shopping for such cleaners. There are, however, other factors to consider as well, so it would be a mistake to think that buying the right air filtration system is a simple matter of picking the unit with the highest MERV.


    John P. Lapotaire, CIEC
    Certified Indoor Environmental Consultant
    Microshield Environmental Services, LLC
    www.Microshield-ES.com  www.CFL-IAQ.com



Add a Comment

(Enter the numbers shown in the above image)


Follow jlapotaire on Twitter


Review microshield-es.com on alexa.com
   

[Valid RSS]
Add this Content to Your Site
   


Latest Top (12) News


EPISODE497 - Radio Joe and the Z-man – Using Building Science & EPA’s Moisture Control Guide to Improve Indoor Air!
Today Radio Joe and the Z-man will be discussing how to solve indoor environmental quality problems by using building science fundamentals and the “EPA Moisture Control Guide”. To get at the root of IEQ problems you must understand buildings and building science. Today we will discuss some great information from people like Joe Lstiburek, Terry Brennan, Bill Rose, Mike McGuinness and Lew Harriman. We start with an overview of building science concepts that will help you solve problems. Our foundation will be the 4 P’s (people, pollutant, pathway, pressurization). From there we will go into how to use the wealth of information in the EPA “Moisture Control Guide” and then go through some case studies. On a future show we will get into how to include the information in your reports

Thu, 11 Oct 2018 11:00:00 -0500


EPISODE496 - Nate Adams The Evolving World of Home Performance The Home Com
Today on IAQ Radio we welcome Nate Adams the founder of Energy Smart Home Performance outside Cleveland Ohio. This week we will talk about â??The Evolving World of Home Performanceâ??. What was once called an energy audit is now evolving into something different. The energy programs are changing and the people that perform/ed energy audits are changing how they market their services and what they provide. Some have gone into healthy housing others are pitching home performance and much more comprehensive and costly changes to existing homes. Nate has a unique perspective on the topic and has released the first edition of his book on the topic. We will explore the topic in detail today on an IAQ Radio+ episode. Nateâ??s company Energy Smart started out as an insulation contractor for existing homes, but has evolved into doing Comprehensive Home Performance retrofits. Their projects are somewhere between a simple attic insulation job and a deep energy retrofit. These projects are sweeping in scope with thorough planning process and careful attention paid to what problems the client wants to solve, what the house needs, and what fits within the homeowner budget. No two projects are alike. Through substantial air tightness and insulation upgrades, and sometimes HVAC replacement, homes are made far more comfortable.

Fri, 09 Mar 2018 08:33:00 -0600


EPISODE495 - Sal La Duca - Environmental Assay, Inc.
This week we are bringing back Sal La Duca for part 2 of our discussion on electricity, EMF's & IEQ. Electricity and electric fields are all around us we keep adding them yet we do not know much about how they affect the health of occupants or if they affect health. Is it possible that they have affects we don't understand? We do know that when installed improperly electric systems can cause a variety of issues. We also know how to find improper installations and to how to reduce the potential for exposure. In Part 1 Mr. La Duca walked us through the basics from the generating facility to the wiring in our home. Part 2 will focus on how to evaluate the issues and what equipment is used to help determine if we have issues.

Fri, 23 Feb 2018 09:00:00 -0600


EPISODE494 - Ralph Moon, PhD Michael Bowdoin, Esq
This week we will be finishing up our hurricane coverage series with two gentlemen that are known for seeing the big picture. Dr. Ralph Moon is based in the Tampa, FL region and Attorney Michael Bowdoinâ??s practice is in the Houston, TX area. Both have extensive personal and professional experience dealing with the aftermath of the hurricanes that hit in 2017. Both also work closely with contractors, consultants, building owners, insurance adjusters and others that have been trying to bring things back to normal. We plan a wide ranging discussion of what happened, how the response was handled and how these events will affect our future dealing with large natural disasters.

Fri, 16 Feb 2018 08:22:00 -0600


EPISODE493 - FLASHBACK FRIDAY - Jeff May


Fri, 02 Feb 2018 09:11:00 -0600


EPISODE492 - Radio Joe Reports - Sloan Research to Practice Kickoff & IAQA
Radio Joe is on the road at the IAQA Annual Meeting and last week attended a Sloan Workshop: Roadmap Research to Practice. Radio Joe will be reporting on both events this week and we will debut our new format for the show. The Sloan workshop was put together by Richard Shaughnessy, PhD and Jordan Peccia, PhD. It was a fascinating meeting of about 15 practitioners, 15 researchers and a handful of government representatives from agencies such as EPA, HUD and CDC. It was designed to allow practitioners to let researchers know what we need from research to do a better job helping people live in better indoor environments. This workshop focused on the Microbiome of the Built Environment and included a lot of discussion on mold and water damage topics. Radio Joe will review the presentations by both researchers and practitioners to bring listeners up to speed on what was discussed. The IAQA Annual Meeting is always a highlight of the conference season. This year it was in Chicago and was in conjunction with the ASHRAE AHR Expo. As always there was a huge expo hall with thousands of exhibitors and some excellent presentations at the Hilton Chicago.

Fri, 26 Jan 2018 06:08:49 -0600


EPISODE491 - FLASHBACK FRIDAY - Tiina Reponen, PhD
Radio Joe is on the road at a Sloan "Research to Practice" Conference and will be back live next Friday to report on the event and the IAQA Conference. This week we are playing back a great show with a guest we tried to get for a long time. Tiina Reponen, PhD is a Professor in the Department of Environmental Health, College of Medicine at the University of Cincinnati. As an expert in indoor allergens and mold, she served as the principal investigator in several major laboratory and field experiments on airborne allergens, bacteria and fungi and has directed exposure assessment teams in population-based studies. Dr. Reponen is the Director of the NIOSH-funded University of Cincinnati Education and Research Center (ERC), which includes graduate programs related to occupational health from three colleges: Medicine, Nursing and Applied Science and Engineering. She is currently directing two cohort studies. One is focused on the association between indoor bioaerosol exposures and the development of children's allergy and asthma and the other is focused on the effects of green renovation on indoor air quality and occupants' health.

Fri, 19 Jan 2018 06:00:03 -0600


EPISODE490 - Tony Havics, PE, CIH - Occupational Exposure Limits and Their
This week on IAQ Radio we welcome Anthony "Tony" Havics to talk about how occupational exposure limits are related to limits for the general public. This is a topic that causes a lot of confusion and at times misinformation. Can we use OEL's or should we avoid them altogether? Join us and LEARN MORE on IAQ Radio! Mr. Havics is an Honors graduate from Georgia Institute of Technology with a Bachelor's Degree in Mechanical Engineering and is a registered Professional Environmental Engineer (PE) with over 25 years of experience. He has provided front end investigation, development of plans & specifications, development of work plans, cost estimation, and oversight of numerous facilities for remediation, refurbishing, or decommissioning including a launch pad, dam gates, a baseball stadium, a tire factory with 59 buildings, a biologically contaminated L1011, a hospital, JP-6 fuel tanks, former mental institute, former military buildings, etc. In the field of microscopy, he has performed analysis for asbestos, contaminants in products, other minerals, fibers, fungi, engineering properties, and has testified in federal court as an expert microscopist. Andrew has also performed failure analysis and forensic testing on numerous building products such as roofs, windows, flooring, drywall, piping, etc.

Fri, 12 Jan 2018 06:00:09 -0600


EPISODE489 - Bruce White IAQA First VP Wildfires and IAQ!
This week on IAQ Radio we welcome Mr. Bruce White, Vice President at American Environmental Specialists & IAQA First Vice President. Mr. White's and his company provide IAQ and environmental consulting on a wide range of issues from their Southern California office. We will discuss wildfires and IAQ, Hospital Construction Monitoring, The new OSHA Silica Rule and Mechanical Systems and IAQ. Bruce brings a unique perspective to his consulting, he has been in the environmental business for over 30 years with a wide range of experience in the real world. He started out in the restoration industry and was also part of the early days of asbestos abatement and other types of environmental contracting. From there he has spent almost 20 years as an environmental consultant with a stint working for a large distributor of environmental safety supplies and equipment. He also has a long history of volunteering for industry related associations and is currently the First Vice President of the Indoor Air Quality Association (IAQA). Bruce has numerous tips and techniques to share with listeners and will also share his insights on the future of our industry. LEARN MORE this week on IAQ Radio!

Fri, 05 Jan 2018 06:00:12 -0600


EPISODE488 - Ken Larsen & Mickey Lee - Water Damage Scope of Work..
This week on IAQ Radio we welcome Ken Larsen and Mickey Lee back to the show to continue our hurricane coverage and to discuss tips for how to develop proper scopes of work on water damage restoration projects. Both pros are working in the areas damaged by Hurricane Irma and both are long time water damage restoration pros, contributors to industry standards and instructors. Ken Larsen, CR, WLS, CSDS has been in the restoration industry since 1978. He holds RIA, ACAC and IICRC advanced designations. His career includes 18 years as an independent property restoration contractor, consultant to restorative drying during catastrophes and large loss drying coordination, expert witness, Director of Education for North America's largest disaster restoration contracting organization, and now the author of one of the industry's leading technical resource books on the subject of structural restorative drying - Leadership in Restorative Drying. He is currently an IICRC Approved instructor of WRT, ASD and CDS certificate courses. He is also an RIA instructor of the restoration industry's advanced certification credentials: Water Loss Specialist (WLS) and Certified Restorer (CR). He serves as Chairman for RIA approved Instructors, Trainers and Subject Matter Experts, a sub-committee of RIA's Education Committee. Larsen presently serves as Senior Technical Director for the International Dry Standard Organization (IDSO) and Director of Education for the Restoration Leadership Institute (RLI) and lead consultant for the Restoration Expert Panel (REP). Ken lives with his wife Barbie (yes - really!) in Santa Rosa Beach in Northwest Florida. He can be contacted at ken at drystandard dot org. Mickey Lee is currently a private consultant providing consulting, training, research and writing services in the fields of property damage restoration, psychrometrics, drying science, mold remediation and structural drying after water intrusions. Mr. Lee retired from the Munters Corp (US) in 2011 after serving in various roles for over 20 years. At various points Mr. Lee was Vice-President - Global Technology & Sustainability for Munters AB - MCS and Global and National Technical & Training Manager for Munters Corp (US). He was responsible for training program development, curriculum writing and course facilitation in addition to managing projects for structural drying and restoration of commercial buildings of every type. He also has extensive experience in application of air treatment technology in restorative drying projects, corrosion-control methods, mold mitigation and humidity control in commercial and industrial facilities while working with Munters Corporation - Moisture Control Services Division. Recognizing his vast experience in water damage restoration the IICRC asked him to lead the development of their Commercial Drying Specialist certification. This program completed its' full roll-out in 2009 and continues to be a popular offering. Mr. Lee continues to serve as committee chair for the Commercial Drying Specialist Certification program and also serves on the IICRC S500 Standard and Reference Guide for Professional Water Damage Restoration revision committee.

Fri, 15 Dec 2017 06:00:11 -0600


EPIS. 487 -Mark Springer, Phil Rosebrook, Jr., Pete Consigli -RIA TPA Conf.
This week on IAQ Radio we discuss a topic that gets blood pressure up among some in the restoration world. Third Party Administrators TPAs are a fact of life today in many industries and RIA has been helping their members make the adjustments necessary. This week we welcome two widely respected restoration professionals to IAQ Radio. Mark Springer and Phill Rosebrook are both RIA members and were speakers at the recent RIA Strictly TPAs Fall Conference. We look forward to having them join us along with frequent contributor Pete Consigl. Mark Springer If you know Mark Springer, you probably know when the platitude, How are you doing? comes up in conversation, his likely answer is, Living the dream! Thats because its true. Mark has been married to his high school sweetheart, Angie for 20 years and they have been blessed with five beautiful daughters who, fortunately for Mark, take after their mother. Living in Montana accentuates the dream as he is able to pursue doing things he loves like downhill skiing, bow hunting, competitive shooting, and the mountains in general. Its not all hobbies though, Mark also gets to work all over the great state of Montana helping people who have experienced disasters, primarily from fires and floods. He is the President of Dayspring Restoration, a company that specializes in disaster restoration. Dayspring has 6 locations and about 100 team members. Mark has become a mini, (emphasis on �¢??mini�¢??) celebrity in Montana due to several television advertising campaigns where he flooded and burned his house and then demonstrated to the community the restoration process, (these videos can be viewed at www.calldayspring.com). Giving back to his community and his industry has always been a priority for Mark as he serves on numerous non-profit and trade association committees and boards Phillip Rosebrook Jr., Cr. Phillip is a graduate of the University of Oregons Lundquist School of Business. He worked his way through college in the family restoration business. He filled most all roles in the company including working on the cleaning crew, carpet cleaning, water damage emergency services, and other various restoration and construction related services. He ran the retail and wholesale carpet cleaning division managing several employees and coordinating the installation crews. After college Phillip managed the water damage division and scheduled all company production crews. He managed the branch office in Coos Bay, Oregon and served the Southern Oregon Coast region. The office was in a very rural area of the state with a small population yet the office grew from $300,000 in annual sales to over $1,000,000 under his management. In managing this office he filled every role from Estimator to Marketing Manager. After training the new Manager Phillip returned to the main office with oversight of all branch offices. He served as the Education Committee representative for the Western Chapter of Disaster Kleenup International. In 1997 when the company sold, Phillip moved to Fort Collins, Colorado to assist in opening a new office for Rocky Mountain Catastrophe. He was in charge of training the new manager, developing the marketing campaign, implementing systems and procedures and training the water damage and cleaning staff. The office quickly grew to over $300,000 in monthly sales. Phillip joined his father as a Partner in Business Mentors in March of 1998. He specializes in implementing change in restoration companies. He works with the individual managers, key employees and sometimes even the field staff to implement new systems and procedures. He developed the Operations Manual and Personnel Manual that is utilized in all of Business Mentors consulting. He is a frequent presenter at industry conferences, contributing author to the WLI course book and has authored many articles in Cleaning and Restoration magazine. Phillip is the founding partner of ELC Training a training resource for restoration companies. He is also a faculty member of the Restoration Leadership Institute. Phillip is the father of four children and has been married to Deanna since 2000. He enjoys gardening, hiking, and cycling. Phil lives in Portland, Oregon.

Fri, 08 Dec 2017 06:00:02 -0600


EPISODE486 - Sal La Duca - Principle Environmental Assay, Inc.
This week on IAQ Radio we are going to talk about an IEQ issue we do not hear a lot about, electricity and electromagnetic frequencies (EMF's). EMF's and other issues related to electrical currents are increasingly part of our indoor environment, we keep adding them yet we do not know much about how they affect the health of occupants or if they affect health. Is it possible that they have affects we don't understand? We do know that when installed improperly electric systems can cause a variety of issues. We also know how to find improper installations and to how to reduce the potential for exposure. Sal will walk us through the issue in layman's terms and give us ideas on how to find and fix issues. LEARN MORE this week on IAQ Radio! Sal La Duca is an Environmental Consultant specializing in the built environment, with over 40 years' experience in instrumentation and controls. Mr. La Duca started out as a Nuclear Reactor Operator / Reactor Technician (Instrumentation and Control Technician - Nuclear) on the USS Mississippi . After discharge, he was offered employment by Jersey Central Power and Light to help built a Radiological Survey instrument repair facility at their Oyster Creek Nuclear Power Plant in Forked River, NJ. From there he migrated to the Communications department, where he performed installation, calibration, and repairs of various generations of remote-control supervisory equipment for power system control. In 1994 he incorporated and began offering Electromagnetic Field services to clients. In 1999 he sought and acquired additional training with the Institute of Building Biology and Ecology, and expanded service offerings to include Indoor Air Quality. Since then he has added IAQ certifications through IAQA and ACAC. Most importantly he has real world experience on residential, commercial and industrial projects and takes a practical approach to the topic. LEARN MORE this week on IAQ Radio!

Fri, 01 Dec 2017 06:00:22 -0600
Follow Microshields IAQ News and Headlines Bloglines RSS Feed

Subscribe with Bloglines

 



IAQ News and Articles

Latest Top (10) News
http://recordings.talkshoe.com/rss1547.xml