How to Test the Air Quality in Your Home (Without Wasting Money)

The air inside your home is often more polluted than the air outside it, sometimes several times over, and the outdoor AQI on your weather app tells you nothing about it. Cooking, cleaning products, furniture, humidity, and poor ventilation all shape the air you actually breathe for the ~90% of your time you spend indoors. The good news: you can test it yourself, and most of it does not require paying anyone.

This guide covers what is worth measuring, the methods that actually work for each one, and how to read the results, so you spend money only where it counts.

Start by knowing what "air quality" is made of

"Air quality" is not one thing. Testing your home means checking a handful of distinct measurements, each with its own sources and its own method:

• PM2.5 (fine particles): from cooking, candles, smoke, outdoor infiltration. The single most health-relevant pollutant indoors.
• CO2 (carbon dioxide): a proxy for ventilation. High CO2 means the air is stale and under-ventilated, and it dulls concentration.
• Humidity: too high (>60%) breeds mold and dust mites; too low dries out airways.
• VOCs (volatile organic compounds): off-gassing from paint, furniture, cleaners, air fresheners.
• Radon: a colourless, odourless radioactive gas from the ground; the second-leading cause of lung cancer.
• Carbon monoxide (CO): from faulty combustion appliances; acutely dangerous.

You do not need to test all six with equal urgency. Below, each gets the method that fits it.

Method 1: A continuous air-quality monitor (PM2.5, CO2, humidity)

For the everyday pollutants, PM2.5, CO2 and humidity, a continuous electronic monitor is by far the most useful tool. Unlike a one-time test, it logs values over hours and days, which is what reveals the real story: the PM2.5 spike every time you cook, the CO2 climbing past 1,000 ppm in a closed bedroom overnight, the bathroom humidity that hits 85% after every shower.

A single reading at noon would miss all of that. Air quality is a moving target, and the pattern over time is the information. A portable monitor you can carry from the kitchen to the bedroom to the basement lets you map the whole home instead of guessing.

What good looks like, as rough targets:

Method 2: A radon test kit (do this once, everywhere)

Radon is invisible and cannot be caught by any air-quality monitor, so it needs its own dedicated test. Inexpensive charcoal or alpha-track radon kits (often $15–$30) sit in your lowest occupied level for a few days to months, then go to a lab. Many regions offer free or subsidised kits. The EPA action level is 4 pCi/L; above that, mitigation is recommended. Every home should be tested at least once, because radon levels depend entirely on the ground beneath you and cannot be predicted from your neighbours.

Method 3: Carbon monoxide alarms (safety, not measurement)

CO is an acute hazard, not a comfort metric. Every home with any combustion appliance (gas stove, furnace, fireplace, attached garage) needs UL-listed CO alarms on each level and near sleeping areas. This is a safety device, not a diagnostic one, but it belongs on any honest "how to test your air" list.

Method 4: Professional testing (when you need certainty)

For specific worries, professional testing gives a definitive answer that consumer gear cannot:

• Suspected mold: an inspector takes air samples with spore traps (indoor plus an outdoor control) for lab analysis. See our guide on mold detectors and what they can't do.
• Asbestos or lead: never DIY. These require certified sampling and labs.
• Whole-home VOC profiling: specialised labs can identify individual compounds a consumer VOC sensor only lumps together.

How to actually run a home test, step by step

1. Set a baseline. Put a monitor in the room you use most and let it run for a full day and night without changing your habits. This is your "normal."
2. Test your suspects. Move it to the kitchen and cook a meal; watch the PM2.5. Close the bedroom door overnight and check the morning CO2. Run a shower and watch bathroom humidity.
3. Test radon in your lowest lived-in level, in parallel, with a kit.
4. Confirm the alarms. Make sure CO (and smoke) alarms are present and in date.
5. Compare to the targets in the table above, and act on whatever is consistently over.

What to do with bad numbers

• High PM2.5: vent while cooking with a range hood that exhausts outdoors, cut candles/incense, and run a correctly-sized HEPA purifier.
• High CO2: ventilate, open a window, crack the bedroom door, or improve mechanical ventilation. CO2 itself is the signal that fresh air isn't reaching you.
• High humidity: use exhaust fans, a dehumidifier, and fix leaks; keep RH under 60% to starve mold.
• High radon: contact a certified radon mitigation professional.

The bottom line

Testing your home's air is really several tests, matched to what you are looking for: a continuous monitor for PM2.5, CO2 and humidity; a one-time radon kit; CO alarms for safety; and professional sampling for mold, asbestos or lead. The most useful everyday tool is the one that logs continuously, because indoor air changes by the hour and the pattern is the point.

Partycle reads PM2.5 and humidity continuously and is small enough to carry room to room, so you can map your whole home and see exactly when and where the air turns, rather than guessing from a city-wide forecast.

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Sources

• US EPA. "Indoor Air Quality" and "Introduction to Indoor Air Quality": indoor air is often more polluted than outdoor air; ~90% of time spent indoors. epa.gov/indoor-air-quality-iaq
• US EPA. "A Citizen's Guide to Radon": 4 pCi/L action level and testing guidance. epa.gov/radon
• WHO (2021). Global Air Quality Guidelines: 24-hour PM2.5 guideline of 15 µg/m³. who.int
• ASHRAE. Ventilation and indoor CO2 guidance underpinning the ~1,000 ppm threshold for adequate ventilation.