Joseph L. Sbarra, CIH
Certified Industrial Hygienist with > 35 years experience
So it's time to replace the air filter to your furnace or HVAC (Heating, Ventilation, and Air Conditioning) system. That’s great, because an air filter can have a significant and positive impact on the air quality in your home.
I’m sure that you have noticed that there are lots of choices out there, and it’s really confusing. Also, what do MERV, FPR, and MPR mean anyway??
Let’s take a look...
Air Filter Rating Systems
MERV, FPR, and MPR are rating systems for air filters, including those used in household furnaces and HVAC systems. The good news is that you really only need to pay attention to one of them: MERV
There is an organization called the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). They have a standard called “Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size” (ASHRAE 55-2017). Translation: It is standardized method for evaluating how effective air filters are at stopping different sizes of particles.
It is the only scientifically recognized and standardized rating system for air filter efficiency that exists in the United States.
MERV (Minimum Efficiency Reporting Value) is a rating system that is part of the standard. Essentially, the higher the MERV rating for an air filter, the higher the efficiency of particle removal.
We’ll talk more about MERV in a minute, but I want to discuss FPR and MPR.
FPR stands for Filter Performance Rating, and it is a rating system developed by one of the large home improvement stores; it appears to be more marketing-based than science-based. It is unclear what methods have been utilized for this rating system, and it is not available for scientific review.
MPR stands for Micro-particle Performance Rating and it is a rating system developed by 3M. This system likely has some science behind it, but it is exclusive to 3M and nobody else is using it.
My advice: If an air filter manufacturer is not going to use the MERV rating system that is recognized nationally, then simply don’t use their products!
The MERV Rating System
The MERV system rates removal efficiency by particle size. The MERV system goes from 1→ 16. Below is a table that provides a basic summary of the MERV ratings, removal efficiency by particle size and typical applications:1
Table Note: µm = micrometer or micron. 1 µm = .001 meters (one one-thousandth of a meter).
The table above is is a simplified summary of information from the ASHRAE standard; what is not included are the overlapping efficiencies by particle sizes. For instance, a MERV 12 air filter has a 20% removal efficiency for particles in the 0.3 - 1.0 µm range.
You can see that the higher the MERV rating, the more efficient a filter will be at removing smaller particles. You can also see that the removal efficiency varies greatly within each of the four (4) major groups of particle size ranges. For example, for the 1.0 - 3.0 µm range, a MERV 8 air filter only removes 35% of the particles, whereas the MERV 12 removes 80% of the particles.
Also, look at the typical application descriptions as they relate to residential homes:
Choosing a MERV Rating for Your Air Filter
There are several things to consider when choosing what MERV rating you want for the air filter in your home, these include:
Filter Cost - the higher the MERV rating, the higher the cost of the filter. Also, you will also have to replace higher MERV rated filters more often as they trap more particles, and can become overloaded faster than lower-rated filters.
Health - do your or someone in your family have allergies or respiratory problems?
Indoor Air Quality - do you have any of the following that can impact the air quality inside your home?
Environmental Factors - do you live in an area where outdoor dust levels are high, such as city or industrial area?
Furnace/HVAC System Age and Condition - newer systems are generally more efficient than older systems and can generally handle higher MERV-rated filters. Also, a well maintained system will be able to handle the higher rated filters better than a system that is not maintained. Remember, an overloaded filter can put a lot of strain on the blower fan of your furnace/HVAC.
Note: If you are considering using an air filter with a MERV rating > 8, check your furnace/HVAC unit manual to see if there are recommendations on maximum MERV ratings for air filters for the system. If not, I recommend that you buy one (1) air filter and have your HVAC technician take static pressure readings inside the unit to ensure that the furnace/HVAC unit is within operational range.
Buy On-line and Avoid Home Improvement Chain Stores- You will certainly pay less on-line compared to buying from any of the large home improvement stores. In my home, we use MERV 12 filters for our HVAC system. We bought a package of 6 online, at a cost of $7.45 each.
I checked on-line at the home improvement stores for comparison: their filters (similar to MERV 12) cost $13.60 - 15.97 each (that price includes a 20% discount for ordering at least 4).
Beware of Advertising Claims - there are lots of filters out there claiming to remove many things. While there is a grain of truth to these claims, you are really being mislead. For instance, there are MERV 11 and 12 filter manufacturers claiming to remove bacteria, droplets from sneezing, and cigarette smoke (which are all from the smallest particle range, 0.3 - 1.0 µm). This claim is true, but there is only a 20% removal efficiency for the MERV 11 and a 35% removal efficiency for the MERV 12.
Odors - there are some manufacturers claiming that their air filters can remove odors with baking soda or activated carbon/charcoal.
Volatile Organic Compounds - some manufacturers claim that their air filters can remove volatile organic compounds with activated carbon/charcoal.
Neither odors or volatile organic compounds are test parameters included in the MERV rating system. Additionally, the manufacturers do not provide any scientific evidence to support these claims, so use your judgment.
Good luck with selecting the right air filter for your home and stay safe and healthy!
1 - Summary of information from ANSI/ASHRAE standard: 52.2-2017 “Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size”.
by Joseph L. Sbarra, CIH
Certified Industrial Hygienist with > 35 years experience
How Did Mercury Get in Gymnasium Floors?
From the early 1960’s to the mid 1990’s, schools and other commercial facilities installed polyurethane (rubberized) flooring in indoor gymnasiums, cafeterias and outdoor running tracks and field houses.
Polyurethane flooring became popular as it was less expensive than hardwood flooring, is less resistant to damage, and is easier to maintain. Most commonly, the process involved pouring the floor in three parts:
Some manufacturers’ flooring included a compound that contained a form of mercury called phenyl mercuric acetate (PMA), which was used as a catalyst in production. Even today, 30 - 50 years after installation; floors with the PMA catalyst still emit mercury vapors into the air!
What is Mercury?
Mercury is an element; it is a shiny, silvery metal sometimes also called quicksilver.
It is the only metal that is a liquid at room temperature. Mercury gives off vapors at room temperature; the higher the temperature, the more vapors are released. Mercury vapors are colorless and odorless.
Mercury has historically been used in thermometers, barometers, fluorescent light bulbs and dental amalgams (used for filling teeth).
Are Mercury Vapors a Health Concern?
They can be, the effect on a person’s health depends on a several factors including:
Mercury is a poison, it is not a known cancer-causing agent. Mercury is absorbed into the body primarily by breathing the airborne vapors. Exposure to mercury can affect the central nervous system (CNS), which is very sensitive to mercury. Exposure to lower levels of mercury vapors for prolonged periods of time (which is the most likely case with regard to gym floors) can cause non-specific health effects such as:
Most of the effects of mercury resulting from prolonged low level exposure are reversible, once exposure is terminated and the mercury has left your body. 1
What is the Approach to Dealing with Gym Floors?
There is a basic approach that can be applied to gym floors that contain mercury.
The first step is to conduct bulk testing to determine if mercury is even present. If bulk testing results are below 1 ppm, then no further action is needed.
If the bulk testing results are positive, the next step would be to conduct mercury vapor screening to determine airborne mercury levels. This can be done with a handheld mercury vapor meter that has the capability to detect < 300 nanograms of mercury per cubic meter of air (that's a really small amount!).
Based upon the mercury screening results, a Management Plan would need to be developed to ensure that airborne mercury vapor exposure levels remain below recommended limits. A Management Plan should include:
Lastly, a decision needs to be made with regard to Long-term Planning: manage the mercury gym floor in place or remove it. Several factors should be considered, including:
We Have a Polyurethane Floor…What Do We Do Next?
1. Agency for Toxic Substances and Disease Registry, ToxFAQs TM for Metallic Mercury, March 2001.
Joseph L. Sbarra, CIH
Mold Expert and Certified Industrial Hygienist with > 35 years experience
OK, you have a concern about mold in your home. So how do you go about choosing a mold testing company when there are literally hundreds of mold testing and mold remediation companies?
I have some good news! Armed with some good information, you can feel confident that you have found the right company for the job.
Licensing and Certifications
Did you know that in only a few states in the U.S. have regulations and licensing for mold testing and remediation? Therefore, if you live in a state that does not have mold licensing, any Tom, Dick, or Harry can say “I’m a mold tester!”
States that have licensing for mold include New York, Florida, Texas, and the District of Columbia. State licenses generally involve several days of training, passing a closed-book exam, and periodic refresher training.
A certified industrial hygienist (CIH) is the “gold standard” of certifications as it relates to mold. Industrial Hygiene is the science of protecting and enhancing the health and safety of people at work and in their communities. An industrial hygienist is dedicated to anticipating, recognizing, evaluating, and controlling chemical, physical, and biological hazards (that includes mold!). A CIH is someone who has:
You should also be aware and beware of “certifications” for mold inspectors. These are generally offered by trade organizations and are primarily one day or on-line classes, with open book exams. These so-called ‘certifications” are not considered to be significant within the industrial hygiene profession because just about anyone can obtain one.
Who Not to Choose
Let’s talk about who you should not choose to conduct your mold testing:
Tip: No reputable mold remediation company will perform mold testing. In states like New York that have licensing for mold, it is prohibited for the mold remediation company to perform mold testing and assessment.
Who Should I Choose?
Since it’s a virtual “Wild West” out there when it comes to mold, who can you trust to come into your home or business and tell you what’s really going on?
My advice is for you to choose a professional, Industrial Hygiene company that specializes in mold inspection and assessment. The Industrial Hygiene company is an independent 3rd party who works for YOU! not the mold remediation company or the insurance company.
Notice that I didn’t say mold testing, because simply testing and reporting that mold is present leaves you with the same problem that you started with, only you have a laboratory test that shows some type and quantity of mold is present.
Elements of a Mold Inspection/Assessment
A mold assessment involves much more than testing. The elements of a mold assessment should include the following:
Here’s a step-by-step process you can follow to choose an Industrial Hygiene company to conduct a mold inspection/assessment:
1. Start with a phone call to discuss your concerns. A good company will ask you several questions about your situation to get enough detail to develop a proposal or quote.
2. Ask for a written proposal. The written proposal should have the following:
Tip: If the cost per sample for 24-hour turnaround is a lot more than 48 or 72 hours, you are getting ripped off!!
3. Ask for a copy of the resume of the mold inspector/assessor. Look for experience, qualifications, and credentials: the more, the better. A more experienced person will cost more than a technician, but it’s worth the money. If you can have a CIH (certified industrial hygienist) conduct the inspection/assessment, that would be ideal for you.
Tip: Try to avoid selecting an Industrial Hygiene company who will send a technician to conduct the assessment and then have a senior staff member review and sign the report. It’s very difficult to write a mold assessment report or mold remediation plan when you were not present to do the visual assessment, thermal imaging, moisture measurement, or mold testing. Invariably, an inexperienced technician is going to miss something.
4. Review everything, especially the cost proposal. If you are unsure about something, ask the Industrial Hygiene company about it. Here are some things to watch out for:
Scam Alert! – Some companies will charge you for a “report” and simply give you a copy of the laboratory results, which you have already paid for! Some laboratory reports contain rudimentary interpretation, or even may indicate that removal is recommended. But a laboratory report lacks the key elements of a mold assessment report, especially since it does not have a discussion about findings and results or any detailed recommendations. Below is an example of a laboratory report:
5. Sign a contract. Ask if the Industrial Hygiene company if it carries insurance for professional liability; if not, you may be limiting your rights if there is a problem.
I trust and hope that you find this information helpful in your search for a mold testing company.