There’s nothing like a pandemic with airborne transmission at the helm to make you face the reality of indoor air quality. Air purifiers and filters have become symbols of improved indoor air quality (IAQ) and better health for many. MERV and HEPA filters are in the limelight as buildings strive for protection, but are they the same?
MERV and HEPA filters share similarities, especially their virus-killing ability and limited use in residential buildings. However, the distinctions between MERV and HEPA filters are just as broad, beginning with the description of both terms.
This article discusses whether MERV is better than HEPA and if MERV and HEPA filters are the same. I also look into whether HEPA filters have a MERV rating and the differences between a MERV 13 and a HEPA filter.
Is MERV Better than HEPA?
Most homes with an HVAC (heating, ventilation, and air conditioning) system enjoy a slightly improved indoor air quality. This is due to the system’s filter that removes pollutants from the indoor air. A decrease in pollutants translates to a cleaner home and reduces allergy and asthma symptoms.
Since filters play an essential role, selecting the most efficient, especially regarding your needs, makes sense. However, before choosing the better option between MERV and HEPA, here’s a brief description of each:
MERV (Minimum Efficiency Reporting Value)
The MERV is an air filters’ efficiency scale that the ASHRAE (American Society of Heating, Refrigeration, and Air-Condition) developed in 1987. It rates a filter’s ability to remove contaminants. The rating scale runs from one to 16, with larger numbers indicating a higher filter efficiency.
Each rating has an average efficiency (in percentage) for a particular size range. For example, MERV 1-4 has 60% to 80% filtering efficiency for particles over 10 microns. The highest ratings, MERV 13-16, have an efficiency of >95% to 99% for particles 0.30 to 1.0 microns.
HEPA (High-Efficiency Particulate Air)
These filters can trap various non-living pollutants (particulate matter) and airborne germs (bacteria and viruses) with an efficiency far above MERV filters. HEPA filters have a dense mat of fibers in a unique configuration, allowing them to capture up to 99.7% of pollutants 0.3 microns.
In the air filter world, HEPA filters are the crème de la crème of the bunch. A HEPA filter can capture 99% of three to 10 microns of airborne particles in size and 97.97% of 0.3 to 1.0 micron-sized particles. This efficiency level is for the lowest-rated HEPA filter.
The 99.97% at 0.3-micron rating means if you blow 10,000 0.3 micron-sized particles into a HEPA filter, it’ll only allow three particles through it. So, in essence, HEPA filters are better than MERV filters.
HEPA filters are the most efficient choice for commercial and residential use, followed by filters with MERV 13-16 ratings.
Although filter efficiency is important, it’s not all you consider before selecting a filter for your home. The pollutants it traps, the filter’s lifespan, and the replacement cost are crucial factors to consider. Some filters need replacements once or twice a year, while others need to be changed every three months.
In the end, you want to strike a balance between all factors without compromising on filter efficiency.
Are MERV and HEPA Filters the Same?
Air filters improve indoor air quality by capturing both inorganic and biological pollutants. Whatever your filtration device, it most likely has a filter that traps particulate matter and airborne pathogens. While the contaminants remain in the filter’s beds, fresh air circulates within your space.
There are many filters available, but MERV and HEPA are the most common names you’ll hear. You may believe they are the same or even interchangeable, given how popular they are. However, they share more differences than similarities.
From the previous section’s description, you know that MERV is not a type of filter. Instead, it’s a rating system discloses an air filter’s efficiency. This efficiency expresses a filter’s relative ability to remove particles of a size range from passing through it.
Thanks to the MERV rating, you can compare the filtering efficacy of two or more filters in a “pear to pear” comparison.
HEPA filters, in contrast, are a type of pleated mechanical air filter that is more efficient than other filters with MERV ratings. So, a filter and rating standard can’t be the same. More differences between both include:
Test Processes
An air filter gets a MERV or ASHRAE rating by undergoing laboratory tests according to the ASHRAE Standard 52.2. The test (Dust Spot test) uses particles in a size range of 0.3 to 50 microns, with approximately 20 microns as the average particle size.
The types of particles incorporated in the test include cotton linters, fine dust, and powdered carbon.
The Dust Spot uses ASHRAE-specified synthetic dust and an aerosol generator and measures particle counts upstream and downstream from the filter. The result of the MERV testing procedure is 72 data points, gotten from six measurements and 12 particle sizes.
Conversely, HEPA air filters undergo tests using Mineral Oil, DOP, and other materials that produce dispersed particles of 0.3 microns or smaller sizes. In fact, HEPA filters are the only mechanical air filters that have tests to prove a specific efficiency at a precise particle size.
HEPA air filters are also the only mechanical filters certified in the same category – they meet a specific efficiency at a particular particle size.
Efficiency
A 100% efficient filter would trap all particles in a given size range, and the air that’s passed through it would have nil particles. However, neither MERV nor HEPA filters are 100% efficient.
You get a 99.97% minimum efficiency at removing 0.3 micron-sized particles with a HEPA filter. If you were to apply the HEPA test on a 95% MERV air filter, you would get around 50% minimum efficiency on 0.3 micron-sized particles.
Despite these differences, some MERV and HEPA filters are alike in one aspect: they are unsuitable for many HVAC systems. Filters with MERV 13 rating and above and HEPA filters are airtight or extremely fine, restricting airflow. This can increase the workload of your HVAC unit, with resultant mechanical issues.
Do HEPA Filters Have a MERV Rating?
HEPA filters exceed the ASHRAE Standard rating, so they don’t have a MERV rating. However, one can informally assign a MERV rating to HEPA filters, and HEPA filters would rate at MERV 17 or higher (up to 20). Many filter manufacturers and industry folks even market filters at MERV ratings from one to 20.
Remember, higher MERV ratings indicate higher filter efficiency (removing pollutants). Filters with the highest ratings can remove particles like pollen, dust, smoke, and even biological growth. So if your family member suffers from allergies or asthma, it’s recommended that you get filters with a high MERV rating.
It’s essential that you understand the variations in MERV values. These values aren’t standard across the board, and they’ll vary from one filter brand to another. Suppose one filter with a MERV rating of 15 can remove VOCs (Volatile Organic Compounds). A different filter with the same rating may not filter at this level: removing VOCs.
What Are the Differences Between a MERV 13 and a HEPA Filter?
Whether you live in an apartment or a house, you may know about replacing filters every year. However, you may have also concluded that all filters aren’t created equal, and some trump others in the efficiency department. Filter ratings and sizes become more vital when you have an HVAC system.
HEPA and MERV filters both eliminate air pollutants in your home, but they are different. If you’re planning to upgrade your home’s filter, understanding these differences helps you make better choices. Here are the differences between a MERV 13 and a HEPA filter:
The Size Range of Particles They Capture
At minimum efficiency—worst performance—a MERV 13 filter traps less than 75% of airborne particles in size range of 0.3 to 1.0 microns. The minimum efficiency increases to 90% or more if you increase the particle size range to 3 to 10 microns. It’s not good at trapping smaller, virus-sized particles such as the coronavirus (0.1 microns)
While a HEPA filter traps 99.97% of particles with a size of 0.3 microns, it can also capture particles smaller or larger. The best part is that the efficiency increases with the changes in particle size.
The Pollutants They Trap and Their Applications
A MERV 13 filter can capture respiratory droplets, bacteria, and tobacco smoke. Such filters find application in the following spaces:
- Commercial buildings like office buildings and supermarkets.
- Residential HVAC units that can handle MERV 13 filters.
- Outpatient facilities like doctor’s offices, nursing homes, etc.
- Some portable air purifiers/filters.
A HEPA filter can capture dust, mold, pet dander, some bacteria, and other airborne particles. HEPA filters find application in the following spaces:
- Medical laboratories.
- Medical facilities, including hospitals and other critical care establishments.
- Pharmaceutical production factories.
- Portable air purifiers.
- Semiconductor manufacturing plants.
Ultimately, your filter choice boils down to your preferences and the filter’s compatibility with your HVAC. Recall that filters with a MERV rating of 13 and above can overload your HVAC system. HEPA filters also have the same constraints, so it would be best to ask an expert for your home’s best fit.