What are HEPA filters and how efficient are they?

HEPA filters are an advanced type of air filter made of thickly woven fiberglass. Often used in hospitals and laboratories, they are highly efficient at trapping indoor air pollutants.

To help explain the technology, below we’ll look into:

  • How HEPA filters work

  • What kinds of contaminants HEPA filters can remove

  • Air purification ratings (and how HEPA compares to other filters)

  • Energy considerations

Interested in a HEPA filter for your home? Call Thornton & Grooms. Our air purification specialists will give you honest advice and up-front prices.

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How does a HEPA filter work?

HEPA stands for “High Efficiency Particulate Air.” Invented in the 1940’s during the creation of the atomic bomb, the filter was designed to protect scientists from harmful airborne toxins.

Made of intricately woven glass fibers, the filter acts like a net, trapping both large and small particles.

For large particles like hair and dust, this makes sense. They simply can’t fit.

For small particles though, scientists uncovered that these particles move in a zigzag pattern. As they try to pass through the HEPA filter, they end up bouncing around — essentially getting stuck within the maze of glass fibers.

To function properly, HEPA filters need periodic testing, cleaning and eventual replacement.

Additionally, if you’re going to install whole-home filtration, it will likely need to be handled by a professional. HEPA filters are quite thick, and don’t fit most standard HVAC setups. HEPA filters do not take the place of common AC filters. Typically, they are stand-alone boxes that are installed on the return side of the furnace. The furnace’s internal motor provides its own airflow through the HEPA filter, which is then recirculated into the supply duct. Installing a HEPA filter in place of a regular filter would cause air flow and performance issues with your furnace and AC units.

What kinds of contaminants can a HEPA filter remove?

HEPA filters can remove 99.97% of airborne particles — including microscopic matter.

This includes large particles, such as:

  • Lint

  • Pollen

  • Dust mites

  • Human hair

  • Carpet fibers

As well as smaller particles, such as:

  • Pet dander

  • Candle smoke

  • Tobacco smoke

  • Humidifier dust

  • Lung-damaging dust

And even microbial contaminants, such as:

  • Mold

  • Bacteria

  • Viruses

How is air purification rated, and how do HEPA filters compare?

Most air filters are rated by a system called MERV, which stands for “Minimum Efficiency Reporting Value.”

MERV values are scaled from 1-16. If an air filter can trap smaller pollutants, the higher its MERV value will be.

For example, if an air filter can only trap large particles like hair and dust, its MERV value will be around 1-3. But if it can trap smaller particles like mold spores or smoke, its value will be around 9-13.

HEPA filters are so efficient, they actually fall outside standard MERV ratings. However, if one had to be assigned, HEPA filters would probably rate 17-20.

This is one of the reasons why HEPA filters are common inside hospitals and laboratories. They can filter microbial contaminants like viruses and bacteria.

Energy considerations

If you decide to install a HEPA filter in your home, keep in mind that your energy bills may be higher.

Why? Because the more effective an air filter is, the harder your equipment will have to work to blow air through it.

If you’re concerned about a single room in your house, you might consider a portable HEPA filter. This will use less energy, but still purify the air where you need it.

Or, if you don’t quite need hospital-grade filtration, there are many high-MERV filters that work well for common allergens, smoke and even mold. These will use less energy, but still greatly improve your home’s overall air quality.

Want honest advice from a Michigan air quality pro?

Our highly trained specialists will help you find the best air filter for your home and budget. For more than 80 years, customers have trusted Thornton & Grooms for honest advice and up-front, transparent prices.

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