How to Test Indoor Air Quality at Home

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What to Measure and Why It Matters

Indoor air contains several distinct categories of pollutants. A single monitor rarely measures all of them well. Before buying a monitor, decide which problem you are trying to diagnose.

**PM2.5 (fine particulate matter)**: The most important measurement for most households. PM2.5 includes dust, smoke, pollen fragments, and pet dander. A laser particle counter gives real-time readings and is the most reliable sensor type in consumer monitors.

**VOCs (volatile organic compounds)**: Gases off-gassed from furniture, flooring, cleaning products, and cooking. Consumer VOC sensors (typically metal oxide sensors) give relative readings, not absolute concentrations. They are good for detecting VOC events (cooking, a fresh piece of furniture off-gassing) but cannot accurately identify specific chemicals or concentrations.

**CO2**: Indicates ventilation adequacy. Outdoor CO2 is ~420 ppm. Above 1,000 ppm in an occupied room indicates poor ventilation. Above 1,500 ppm causes measurable cognitive impairment in most people. An accurate CO2 sensor uses NDIR (non-dispersive infrared) technology; avoid monitors that estimate CO2 from VOC readings.

**Humidity**: High humidity (above 60%) promotes mold and dust mite growth. Low humidity (below 30%) dries mucous membranes and increases susceptibility to respiratory irritants.

Consumer Air Quality Monitors Worth Considering

**Awair Element ($150)**: Measures PM2.5, VOC, CO2, temperature, and humidity. Uses a laser PM2.5 sensor and NDIR CO2 sensor. The most accurate mid-range option for the full set of measurements. App tracks historical trends.

**IQAir AirVisual Pro ($270)**: Best-in-class CO2 sensor accuracy, PM2.5, temperature, and humidity. Displays AQI in real time. Also integrates outdoor AQI data from nearby stations for comparison. More display, less design focus.

**Govee Air Quality Monitor ($50)**: PM2.5, PM10, temperature, humidity. No CO2 or VOC. Good for particulate-focused monitoring on a budget. Less accurate at the lowest PM2.5 concentrations but adequate for detecting cooking smoke, wildfire infiltration, and general dust events.

What Consumer Monitors Cannot Tell You

VOC sensors cannot identify which specific chemicals are present or at what concentrations. If you suspect formaldehyde (from new flooring, furniture, or particleboard), a specific formaldehyde test strip or lab test is more reliable than a broad VOC reading.

PM sensors count particles by size using light scattering but cannot distinguish between particle types. A monitor showing elevated PM2.5 cannot tell you if that is dust, pollen, or wildfire smoke.

For mold, radon, asbestos, or lead, consumer monitors are not the right tool. These require lab testing or certified professional inspection.

When to Use a Lab Test Instead

Consider a lab test if:

You want quantified formaldehyde or specific VOC readings after renovation or new furniture installation
You suspect mold growth and need documentation for remediation or insurance
Radon screening (EPA recommends testing all homes below the third floor)
Asbestos or lead concern in pre-1980 construction

The EPA's Indoor Air Quality website lists certified testing services by state. Radon test kits are available at hardware stores for $10-25; mail-in analysis is included in the kit price.

Simple Baseline Test Without a Monitor

If you do not want to buy a monitor, a useful baseline: open windows on a low-outdoor-AQI day for 30 minutes, then close up and smell for persistent musty, chemical, or stale odors over the next hour. Persistent odors after fresh-air flush indicate an indoor source. No persistent odor after a fresh-air flush usually means the building's air quality is adequate for most households.

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