Gear guide · Air · updated October 12, 2026

Indoor air quality monitors

You can't manage what you don't measure. A particle (PM2.5) reading shows when wildfire smoke or cooking particles have built up indoors, and whether a purifier is keeping up. CO₂ shows whether the house is under-ventilated for the people in it, the same question an energy auditor answers with instruments. Humidity doubles as a mold early warning: EPA advises keeping indoor humidity below 60%, ideally between 30% and 50%.

Not sure this category applies to your home? The testing guide covers which tests matter. For the testing side, see the mold & indoor air guide.

A heat recovery ventilator on a basement wall with four insulated ducts running up between the joists

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The everything monitor

Airthings View Plus

Radon, PM2.5, CO₂, VOCs, humidity, temperature and air pressure on one display. One device gives you a whole-home baseline, radon included.

$330 list

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The CO₂ meter

Aranet4 Home

An NDIR CO₂ sensor with an e-ink display and up to four years on a set of batteries (the maker's figure). Watch the number climb in a full room with the doors shut: readings that stay high make the case for better ventilation.

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The budget particle counter

Amazon Smart Air Quality Monitor

PM2.5, VOCs, carbon monoxide, humidity and temperature at a low price: enough to see smoke getting in and to check where a purifier works. It has no CO₂ sensor, and its CO reading doesn't replace a UL 2034 CO alarm.

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Prices are rough US list prices from each maker's own website, checked October 12, 2026. Where we couldn't confirm a current US price, we left it off rather than guess. Amazon prices move and often run below list, so check the live listing.

Before you buy

  • On smoke days, watch indoor PM2.5 with the purifier running. If the number keeps climbing, the purifier is too small for the room or in the wrong spot.
  • At household levels, CO₂ is mainly a ventilation signal: it tells you when to air out a room and when mechanical ventilation would pay off.
  • EPA's humidity target is below 60%, ideally 30% to 50%. Basement readings that stay above that are the cue for a dehumidifier.
  • A monitor is not an alarm. Keep UL 2034-listed CO alarms on every level and outside sleeping areas, as CPSC recommends.

Sources

Some links here are affiliate links — as an Amazon Associate, AuditYourHome earns from qualifying purchases, at no extra cost to you. Picks are chosen on merit; no manufacturer pays for placement, and prices shown are planning bands, not quotes.

Also in gear guides: Radon monitors & test kits · Air purifiers (HEPA) · Carbon monoxide alarms