Buyer’s Guide: Air Filtration

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Portable HEPA filter units

>>For more on ridding allergens from your bedroom, read the post HERE.

One option is a portable high-efficiency particulate air (HEPA) filter unit. HEPA filters are required to remove at least 99.97% of airborne particles 0.3 micrometers in size.

Some HEPA filters are marketed as “True HEPA” which simply means they follow this standard. (“HEPA-type”, “HEPA-like”, and other similar terms may not meet the HEPA standard.)

These portable units have at least two filters. First, a primary carbon filter that traps large particles of dust (and cat fur) plus odors. And a second filter that traps the smaller molecules, such as pollen and smoke.

If you use your unit 24/7, the primary filter needs to be replaced about every 6 months—or when your unit tells you. Replacement filters are easily found online.

The second filter is replaced rarely. I have yet to be instructed to change it.

Look for units with high clean air delivery rate (CADR) ratings. The CADR is the cubic feet per minute of air that has all the particles of a given size removed. The bigger the number the better.

(Presumably, these CADR ratings are on the highest—loudest—setting.)

And yes, true HEPA filters remove virus particles as well.

Two sizes are available depending on the size of your room and your desired CADR ratings.

Note, I purchased the more expensive model with WiFi and Bluetooth, however, I found those features to not be particularly useful with this unit.

The large air quality indicator light is bright, and it doesn’t turn off. For bedroom use I turned the unit backward, facing the light into a piece of furniture. (Air input is on the back; output is via the sides.) I covered the top with a washcloth.

This unit also comes with a UV light, which also probably doesn’t sanitize much as air is moving too quickly through the unit. However, if you are concerned about virus particles in your home in 2020, an air purifier with UV light is recommended by ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers).

My unit has five speeds (the first one listed above has three), including an auto feature that turns on when particles are detected (eg, when I change my bedding). However, this auto feature appears not to be available in the less expensive models.

All units have a timer.

Keeping the speed at 1 or 2 is quiet enough for a bedroom, although there is a bit of white noise.

If shopping for the bedroom, take note of the noise your unit may produce. I also have an older budget HEPA filter unit made by Honeywell, that is quite loud on the lowest setting. Day time use only.

Other highly rated units to consider:

  • Hathaspace Smart True HEPA Air Purifier. Auto air quality sensor that adjusts the fan. Five stage filtering (via two replaceable filters). Covers 350 sq ft. with CADR of 160. “Whisper-quiet” sleep mode of 18 dB.
  • Medify MA-18. Medical-grade HEPA (0.1 micrometers) filtration, covers 400 sq ft with CADR 150. (Reviews describe it as “quiet”.)
  • Medify Air MA-112. For serious filtration! Three-stage medical-grade filtration that covers 2,400 sq ft with CADR of 950!

Filter units for your Furnace/AC

Note, these do not meet the standard of a HEPA filter, which would block airflow if installed in your HVAC system.

But they are far superior to the generic filters installed in your current system. You change your filter regularly, right?

With regular use, filters should be changed at least every 3 months. (More often with pets.)

Compare different MERV, or minimum efficiency reporting value ratings. The higher, the better, or the more things that are filtered out.

3M, the company that makes these filters, also has an additional measurement, called the MPR or microparticle performance rating. This rating focuses on particles between 0.3 and 1 micrometers in size.

Don’t forget to measure your filter so that you purchase the correct size.

For even greater air filtration, Filtrete “Healthy Living” filters are also available in MERV 13 / MPR 1900.

As well as MERV 14 / MPR 2800.

These filters are not going to do any good if you have leaks in your HVAC airducts

A leak could be pulling in dusty air from your attic. If it’s been a while, an inspection from a qualified HVAC technician may be in order.

Important 2020 Update

According to ASHRAE, to filter out virus particles, the MERV rating should be 13 or higher.

In addition, when possible, increase ventilation with outdoor air.

Smart Air Filters

It was inevitable. Even air filters are now equipped with Bluetooth.

Download the iOS or Android app and measure air pressure. If the air pressure is consistently too high this will indicate that your filter needs to be changed.

The app also reports outdoor air quality.

You no longer need to blindly replace your filter every three months, especially if you don’t run your HVAC consistently.

Filtrete’s MERV 12 / MPR 1500 filters are also available in a Smart version.

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