If you feel better when you leave your house and worse when you come back, your home may genuinely be making you sick. The pattern is the single most important clue: symptoms like headaches, throat irritation, fatigue, dizziness, and difficulty concentrating that ease up shortly after you leave the building point toward indoor environmental problems. Testing your home means systematically checking for the most common culprits, starting with the ones most likely to cause harm.
Track the Symptom Pattern First
Before spending money on test kits, pay attention to when your symptoms show up and when they disappear. The EPA identifies a cluster of complaints tied to problem buildings: headaches, eye and nose irritation, dry cough, itchy skin, dizziness, nausea, fatigue, sensitivity to odors, and trouble concentrating. Most people report relief soon after leaving the building. Keep a simple log for one to two weeks noting which symptoms appear, what time of day, which rooms you were in, and how quickly they resolve once you’re out of the house.
If your symptoms are constant regardless of location, the cause is less likely to be your home. But if there’s a clear on/off pattern tied to being indoors, that narrows the investigation considerably. Also note whether symptoms are worse in specific seasons. Problems that flare in winter often point to poor ventilation or dry air from heating systems. Symptoms that spike in humid months suggest mold or dust mites.
Test for Radon
Radon is an odorless, colorless gas that seeps into homes from the ground. It’s the second leading cause of lung cancer, and you cannot detect it without a test. The EPA recommends taking action if your home’s radon level reaches 4 pCi/L (picocuries per liter) or higher, and suggests considering mitigation even between 2 and 4 pCi/L because there is no known safe level of exposure.
Short-term test kits are available at most hardware stores for under $20. You place the kit in the lowest livable level of your home, typically the basement or ground floor, and leave it for two to seven days with windows and exterior doors closed. You then mail it to a lab and get results within a couple of weeks. If the short-term test comes back at or above 4 pCi/L, follow up with a long-term test (90 days or more) to get a more accurate annual average. Radon levels fluctuate with weather and season, so the long-term reading gives you a better picture of your actual exposure.
Check Your Water
What you need to test for depends on where your water comes from. If you’re on a private well, you are responsible for testing, and the recommendation is to do it at least once a year. The priority contaminants for well water are bacteria (especially coliform and E. coli), nitrates (common near agricultural land), iron, manganese, and hardness. Nitrates are particularly dangerous for infants and pregnant women. Your local health department or cooperative extension office can point you to certified labs, and many offer low-cost well water screening.
If you’re on municipal water, your utility is required to test and publish an annual Consumer Confidence Report. But that report covers water as it leaves the treatment plant, not what comes out of your tap. The pipes between the street and your faucet can introduce lead, especially in homes built before 1986, which are more likely to have lead pipes, fixtures, and solder. Municipal systems also carry chlorine disinfection byproducts, trace pharmaceutical residues, and increasingly, PFAS (per- and polyfluoroalkyl substances, sometimes called “forever chemicals”). A point-of-use test kit or a certified lab test on a first-draw sample from your kitchen tap in the morning will tell you what’s actually in your drinking water after it travels through your home’s plumbing.
Inspect for Mold (Don’t Rely on Fancy Tests)
Mold is one of the most common reasons a house makes people sick, and it’s also one of the most over-tested. The EPA does not recommend the ERMI (Environmental Relative Moldiness Index) for home use. It was developed as a research tool and is not intended for individual homeowners trying to make decisions about their living spaces. Standard air sampling with spore traps can also be misleading because mold spore counts vary dramatically from hour to hour.
A thorough visual inspection is more useful than most lab tests. Check under sinks, around toilets, behind refrigerators, in attics, along basement walls, around window frames, and inside HVAC ducts. Musty smells in a room with no visible mold often mean growth behind walls or under flooring. If you find a patch smaller than about 10 square feet, you can typically clean it yourself with detergent and water. Larger areas, or mold inside wall cavities or HVAC systems, warrant a professional remediation company.
If you suspect hidden mold but can’t find it, hiring a certified indoor environmental professional to do a targeted inspection (including moisture mapping with thermal imaging) is more valuable than mail-order test kits. They can pinpoint moisture intrusion, which is the root cause. Without fixing the moisture source, mold always comes back.
Measure Indoor Humidity
A digital hygrometer costs about $10 to $15 and tells you something genuinely useful: your indoor relative humidity. The EPA recommends keeping it between 30 and 50 percent, and no higher than 60 percent. Above 60 percent, condensation forms on surfaces and mold growth becomes likely. Below 30 percent, you get dry skin, irritated airways, and cracked mucous membranes that make you more susceptible to respiratory infections.
Place the hygrometer in the room where you spend the most time, and check it across different seasons. If humidity consistently runs high, a dehumidifier or improved ventilation (bathroom exhaust fans, range hoods vented to the outside) can bring it down. Dust mites also thrive in humid environments, so controlling moisture addresses two problems at once.
Test for Lead if Your Home Is Older
Homes built before 1978 may contain lead-based paint. The federal government banned consumer uses of lead paint that year, though some states banned it earlier. Lead paint in good condition and covered by newer layers is generally low-risk. The danger comes when it’s peeling, chipping, or disturbed during renovations, releasing fine dust that you inhale or that settles on surfaces where children touch it.
You can buy EPA-recognized lead paint test swabs at hardware stores. They change color on contact with lead and give results in 30 seconds. Test windowsills, door frames, trim, and any areas with chipping or flaking paint. For a more comprehensive assessment, especially before renovation, hire a certified lead inspector who uses an X-ray fluorescence (XRF) device that can detect lead beneath multiple layers of paint without disturbing the surface.
For water, request a lead-specific test from a certified lab. Collect a “first draw” sample, meaning the first water out of the tap in the morning after pipes have sat overnight. This captures the highest concentration of any lead leaching from your plumbing.
Assess Your Ventilation
Poor ventilation is the invisible thread connecting many indoor air problems. When fresh air can’t circulate in, pollutants from cooking, cleaning products, off-gassing furniture, and human respiration accumulate. Modern homes that are tightly sealed for energy efficiency are especially prone to this.
A carbon dioxide monitor (typically $50 to $150) offers a practical proxy for ventilation quality. Outdoor CO2 levels hover around 400 ppm. If your indoor reading regularly climbs above 1,000 ppm, your space isn’t getting enough fresh air exchange. Simple fixes include opening windows for even 10 to 15 minutes daily, running kitchen and bathroom exhaust fans, and making sure dryer vents and combustion appliances vent to the outside rather than into the attic or crawlspace.
Carbon monoxide is a separate and more urgent concern. Every home with gas appliances, an attached garage, or a fireplace should have CO detectors on each level. Carbon monoxide poisoning mimics flu-like symptoms (headache, nausea, dizziness, confusion) and can be fatal. If your CO detector alarms, leave the house immediately.
Where to Start
You don’t need to test for everything at once. Prioritize based on your home’s profile and your symptoms:
- Every home: Radon test kit, CO detectors, and a hygrometer. These are cheap, cover the most dangerous exposures, and take minimal effort.
- Homes built before 1978: Lead paint test swabs on any deteriorating painted surfaces, plus a first-draw water test for lead.
- Homes on well water: Annual bacteria and nitrate testing at minimum.
- Homes with musty smells, visible staining, or recent water damage: Targeted mold inspection focusing on moisture sources.
- Homes with persistent stuffiness or respiratory symptoms: CO2 monitor to evaluate ventilation, followed by HVAC inspection if readings are high.
Most of these tests cost between $10 and $50 when you do them yourself, and results come back within days to a couple of weeks. If initial testing doesn’t reveal a clear cause but your symptom pattern still points to the house, a certified indoor air quality professional can conduct a broader assessment covering volatile organic compounds, particulate matter, and combustion gases that consumer-grade kits don’t capture well.