MERV 8 filters cannot filter smoke. MERV 8 filters can capture particles of 3 microns or larger, which means they are good at trapping dust, dust mites, pollen, bacteria, hairspray, and pet dander from one pet, but they are unable to trap fine particles.
However, a MERV 8 filter captures greater or equal to 20% of particles between 1.0 and 3.0 microns and is not rated to filter particles or pollutants between the sizes of 0.30 and 1.0 microns. That means things like pet dander, smoke, and some airborne bacteria are likely to get through a MERV 8 filter.
Upgrading to a filter rated MERV 13 or higher can be especially important during smoky periods to effectively remove fine particle pollution from smoke in the indoor air. Most furnaces and HVAC systems can accommodate a MERV 13 filter without creating equipment problems, provided that the filter is replaced frequently.
Suitable for Most Homes: MERV 8 filters are effective at capturing larger particles like dust, pollen, and pet dander. For many homes, especially those without specific indoor air quality concerns, MERV 8 filters strike a good balance between filtration and airflow.
MERV 8 air filters are most commonly used in residential buildings. They trap about 80% of airborne particles. Furnace filters with this MERV rating are capable of blocking contaminants that are in the 3.0-10-micron range and other larger particles.
A MERV 8 filter is considered suitable for residential settings, capturing particles like pollen, dust mites, and mold spores.
For most homes, a rating of MERV 8-13 is a good start to keep your air healthy.
The scaling of MERV is not linear; the difference between a MERV 6 and a MERV 8 is nearly double in the percentage of particles captured. Be aware that as the MERV rating increases, the filter gets more restrictive and it will take more pressure and energy to push air through.
The Minimum Efficiency Reporting Value (MERV) rating of the filter strongly impacts the Clean Air Delivery Rate (CADR). It is recommended to use a MERV 13 filter(s) to remove the very small particles in wildfire smoke.
Similar to the previous MERV filters, it is often recommended to replace MERV 8 filters every 90 days. As a side note, make sure to replace you air filter with the right air filter size.
"Since smoke particles are typically within this size range, HEPA filters are excellent for removing smoke from the air, preventing it from entering the respiratory system and causing harm."
A MERV 5 filter will trap up to 34%, MERV 6 will stop 35-49%, MERV 7 will prevent up to 69%, and MERV 8 will catch up to 85% of particles. These filters are slightly more restrictive than the MERV 1-4 filters and have the ability to catch mold spores and some pet dander along with dust and pollen.
Some removal of wildfire smoke particles occurs with MERV 11 filters. We generally recommend MERV 13 or higher if possible (check with an HVAC expert before upgrading your filter). Some companies, such as 3M, may use their own rating system for their HVAC filters. 3M shares the MERV equivalent on their website.
The EPA recommends filters with a rating of at least MERV 13, or, “as high a rating as your system fan and filter slot can accommodate.” MERV stands for “minimum efficiency reporting value,” and it is a measure of how well a central-air filter removes particulates from the air.
HEPA filters are not MERV-rated because they exceed the ASHRAE Standard rating system. Informally, however, if HEPA filters were to receive a MERV rating, they would rate roughly at MERV 17 or higher.
The primary drawback of high MERV filters is that the pressure drop across them is too high, which can lead to reduced airflow and increased energy consumption in HVAC systems. This resistance may strain mechanical components over time, potentially causing failure.
As a result, MERV 8 filters capture mid-size particles such as aerosol sprays, mold and dust. For most homes, this isn't nearly enough. Harmful viruses and bacteria will still circulate through your home, as well as smoke and other forms of air pollution.
For smoke removal, HEPA filters are recommended as the gold standard for trapping fine particles, filtering out 99.97% of particles 0.3 microns in size.
Determine Your Air Filter Needs
In that case, you may want to consider a higher Minimum Efficiency Reporting Value rating of 9 to 12. While for homes with smoke or a fireplace, you should opt for a MERV rating of 13 to 16. Filters with these ratings are intended for trapping and removing smoke particles and fumes.
MERV 5 to 8 – effective at controlling mold spores, hair spray, dust. Applicable in most commercial buildings, residences, industrial workplaces and paint booths. MERV 8 filters have 90 percent efficiency on particles that are 3 to 10 micrometers in size.
Considerations for Choosing Between MERV 8 and MERV 13
If you have pets, allergies, or asthma, a MERV 13 filter may be more beneficial. However, remember that higher MERV filters can restrict airflow more than lower-rated filters, potentially impacting your HVAC system's efficiency.
While a typical 2″ MERV8 pleated filter has a pressure drop of . 14″ wg at 300 fpm and a . 27″ wg at 500 fpm.
These high-quality filters trap particles as small as one micron, including Legionella and humidifier dust. MERV 9 to 12 filters are the best filters that a residential HVAC system will accommodate without serious system modifications.
MERV 8 filters capture basic particles like dust, pollen, and pet dander and are adequate for most households. Higher ratings, such as MERV 11 to 13, offer enhanced filtration, capturing smaller particles like mold spores and smoke, which is beneficial for those with allergies.
Air filters with higher efficiency ratings may do a better job clearing the air. Still, they'll also force your HVAC system to work harder, resulting in performance challenges and higher energy bills.