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Independent public directory · Data checked October 2, 2026 · Not a government agency

Indoor air: test it, find the source, filter the rest

What EPA and AirNow say about the air inside a home, and what helps.

  1. Know the number

    Outdoors, the AQI. Indoors, PM2.5, VOCs, and humidity.

  2. Find the source

    EPA: "The most effective ways to improve your indoor air are to reduce or remove the sources of pollutants and to ventilate with clean outdoor air. In addition, research shows that filtration can be an effective supplement to source control and ventilation."1

  3. Filter what is left

    EPA: "Portable air cleaners, also known as air purifiers or air sanitizers, are designed to filter the air in a single room or area. Central furnace or HVAC filters are designed to filter air throughout a home."1

  • Up to 10xmany VOCs, indoors vs outdoors2
  • 2.5 micrometersand smaller: the fine particles called PM2.53
  • 30 to 50%EPA's ideal indoor humidity4
Airthings View Plus showing radon and carbon dioxide readings

A monitor for the air inside

Airthings View Plus: $329.99
Price checked October 1, 2026

Airthings says:5

  • "PM2.5 is fine particulate matter small enough to reach deep into the lungs."
  • "Volatile organic compounds (VOCs) are airborne chemicals released by cleaning products, paint, new furniture, and adhesives."
  • "Indoor humidity above 60% encourages mold growth and dust mites, while levels below 30% cause dry skin and throat irritation."

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Filtering what is left

EPA: "Choose a portable air cleaner that is the right size for the room in which you will use it."6

Airthings Renew

Airthings says:7

  • "HEPA 13 filter removes 99.97% of all particles as small as 0.3 microns."
  • "Activated charcoal filter. Captures and holds gases (VOCs) and odors."

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EPA: "EPA neither certifies nor recommends particular brands of air filters or home air-cleaning devices including portable air cleaners or purifiers."1

Sources

  1. EPA, Guide to Air Cleaners in the Home, checked October 4, 2026
  2. EPA, Volatile Organic Compounds' Impact on Indoor Air Quality, checked October 4, 2026
  3. EPA, Particulate Matter (PM) Basics, checked October 4, 2026
  4. EPA, A Brief Guide to Mold, Moisture and Your Home, checked October 4, 2026
  5. Airthings, View Plus product page, checked October 4, 2026
  6. EPA, Wildfires and Indoor Air Quality (IAQ), checked October 4, 2026
  7. Airthings, Renew product page, checked October 4, 2026

Health facts on this page come from the agencies linked here. About this directory.