Tip/Thought of the Day

Choosing An Effective Air Filter

There are many ways to keep the air in your home fresh- plants, regular cleaning, choosing household items and cleaners low in (or free of) harmful chemicals, and air filters are all great options. There are many options for filters for your home HVAC system and stand-alone filter systems. Today we’ll share how to choose between the levels of filtration and find an option that works for your household.

Stand-alone filtration systems

A stand-alone filtration system may be a good idea if you have a sick individual in your household, or if you find that allergy symptoms worsen in certain rooms. Many people choose to have an air filter in their bedrooms so allergy symptoms won’t hound them and prevent them from getting a good night’s sleep.

As far as COVID-19 goes, current understanding is that the most likely method of transmission is via droplets expelled from the body through coughing, talking, and breathing. Although most of the droplets fall to the ground and dissipate quickly, some research suggests smaller particles may remain in the air for longer.

Choose a HEPA (high efficiency particulate air) filter for best results when using a home filtration system. HEPA filters describe filters that are able to trap 99.97% of particles that are as small as 0.3 microns. Interesting fact: the development of HEPA filters dates back to World War II, when American scientists with the Manhattan Project created the first HEPA filter to capture radioactive particles released during the creation of the atomic bomb. More recently, health organizations worldwide have used HEPA filters to protect against viruses, like in 2003 with the SARS outbreak.

Many air purifiers advertise they include “ionizers” to help attract particles like static. These are negative ions that grab onto dust and allergens in the air. But unlike HEPA filters that don’t produce ozone, ionizing filters do. Ozone is a highly reactive gas and Consumer Reports has warned that some ionizing filters may produce ozone at harmful levels. Those more sensitive (having underlying pulmonary conditions) may experience adverse effects even when exposed to low levels of ozone.

How do HEPA filters work?

Coway, which specializes in air filtration systems, explains why modern HEPA filters are so effective against particles:

Most modern HEPA filters consist of interlaced glass fibers that are twisted and turned in myriad directions to create a fibrous maze. As particles traverse this web, they’re taken out of circulation in the following ways:


 Direct Impaction: Large contaminants, such as certain types of dust, mold, and pollen, travel in a straight path, collide with a fiber, and stick to it.

Sieving: The air stream carries a particle between two fibers, but the particle is larger than the gap, so it becomes ensnared.

Interception: Airflow is nimble enough to reroute around fibers, but, thanks to inertia, particles continue on their path and stick to the sides of fibers.

Diffusion: Small, ultra-fine particles move more erratically than larger ones, so they’re more likely to hit and stick to fibers.

Keep in mind that caution should be used when changing out a HEPA filter- use gloves and immediately dispose of, or wash, the filter as the manufacturer recommends.

What about HVAC filters?

Out of sight, out of mind, right? Many people overlook the importance of replacing and cleaning their HVAC filters. But forgetting to address this simple element can not only directly impact the efficiency and operation of the HVAC system, but also impact the quality of air in your home. If the filter is clogged with dust, hair, and other particles that means that particles in your home aren’t being removed. Set a reminder on your phone, or use the reminder setting available on newer systems.

Choosing a filter

Furnace filters are rated by their minimum efficiency reporting value, or “MERV.” The higher the rating, the more efficient the filter is at trapping airborne particles. The numerical range is from 1 (lowest efficiency) to 20 (highest efficiency). Typically, filters in the 6 to 12 range are designed for residential use-your furnace’s operating manual will recommend the optimal MERV rating. A few options include:

Fiberglass: The least expensive option, fiberglass is also the least efficient, removing only larger particles of dust from the air. For a small difference in price, we recommend choosing a pleated filter (see below), which will offer more protection. MERV rating: 2-3, cost: $1 to $2

Disposable pleated: The disposable pleated option are made of cotton or polyester. The pleating helps trap particles. Combined with the weave of the cotton or polyester, particles are more likely to be contained a they pass through the filter. MERV rating: 6, cost: $4 to $5

High efficiency pleated: This option provides a great layer of protection, but it is an investment. People that experience respiratory problems or autoimmune disorders may benefit from the added filtration. High-efficiency pleated options are made of thick synthetic cotton adhered to a metal grid to ensure the filter stays in place. You’ll likely have to partner with an HVAC expert to fit this kind of filter to your system, as most can’t accommodate the thick filter. MERV rating: 14-16, cost: $100+

Electrostatic: These filters are available in disposable and reusable options made with cartridges containing cotton or paper fibers that attract and trap small particles. The system works by using self-charging layers of cotton/paper fiber to catch particles. Depending on the option you choose, you may replace or clean the filter quarterly or when the system alerts that attention is required. Some people like this option as there is less waste and generally speaking, filters last a long time while continuing to offer protection. MERV rating: 8-10, cost: varies as some may need to be custom ordered.

HEPA: Unfortunately, most home HVAC units aren’t powerful enough to draw air through a HEPA filter. HEPA filters are mainly used in commercial settings and health facilities. But, if you’re looking for the extra layer of protection, choose the most efficient filter for your HVAC system and then add stand-alone HEPA filtration systems as needed.

Other ways to improve air quality on your own include:

  • Keep windows and doors open to increase circulation
  • Use fans throughout the house
  • Run just the fan on you HVAC system
  • Upgrade and replace filters more often than recommended
  • Vacuum often, ideally using a system that is sealed and HEPA certified
  • Use exhaust fans in the kitchen and bathrooms
  • Minimize wood burning fires and candles
  • Never smoke indoors









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