We worry about the air pollution outside, but we rarely think about the air inside our homes. This is a huge oversight, especially when you consider that most of us spend about 90% of our time indoors (EPA). The air in your living room, bedroom, and kitchen has a more direct and sustained impact on your health than the air anywhere else. This guide will walk you through everything you need to know about your home’s air—what’s in it, how it affects you, and most importantly, how to make it healthier.
What Is Indoor Air Quality?
In simple terms, Indoor Air Quality (IAQ) refers to the environmental characteristics inside buildings that may affect human health, comfort, and work performance. It’s a measure of how clean or polluted your indoor air is. When we talk about poor IAQ, we’re talking about the presence of contaminants that can cause health problems, either immediately or over time.
The tricky part is that these pollutants often come from sources we use every day. Your home might look and smell clean, but that doesn’t guarantee the air is healthy. Common culprits include cooking fumes, cleaning products, new furniture, and even your own breath.
Here’s a quick breakdown of the most common indoor air pollutants and where they come from:
| Pollutant | Common Sources |
| Particulate Matter (PM_2.5) | Cooking (especially frying), burning candles, fireplaces, smoking, dust, pet dander |
| Volatile Organic Compounds (VOCs) | Paints, cleaning products, air fresheners, new furniture (off-gassing), cosmetics, craft supplies |
| Carbon Dioxide (CO_2) | Human breath (exhaling), gas stoves, poor ventilation |
| Radon | A naturally occurring radioactive gas that seeps in from the ground through cracks in the foundation |
| Mold & Mildew | Excess humidity, water leaks, damp areas like basements and bathrooms |
Why Your IAQ Matters for Your Health
The link between air quality and health is undeniable. Poor IAQ can trigger a wide range of issues, from subtle annoyances to serious long-term conditions.
Short-Term Effects: These symptoms can appear after a single exposure or repeated exposures and are often mistaken for allergies or a common cold. They include:
- Headaches and dizziness
- Fatigue and trouble concentrating
- Irritation of the eyes, nose, and throat
- Worsening of asthma symptoms
Long-Term Effects: Prolonged exposure to indoor pollutants can lead to more severe health consequences, including the development of respiratory diseases, heart disease, and even cancer (WHO).
Who Is Most Vulnerable? Children, the elderly, and individuals with pre-existing respiratory conditions like asthma or cardiovascular disease are particularly susceptible to the effects of poor indoor air. Their bodies may have a harder time processing pollutants, leading to more severe reactions.
For years, Maria couldn’t figure out why her son’s asthma was worse at home, even with his medication. She kept the house spotless. It wasn’t until a home energy audit revealed extremely high levels of airborne dust and poor ventilation that she connected the dots. Improving her home’s filtration and airflow made a world of difference for her son’s breathing.
How to Measure Your Indoor Air Quality
You can’t fix what you can’t measure. While you can sometimes smell mold or see dust, many of the most harmful pollutants are invisible and odorless. This is where an indoor air quality monitor comes in. These devices provide real-time data on the key indicators of your home’s air.
When looking at a monitor, you’ll typically see readings for three key things:
- PM_2.5: Fine particulate matter smaller than 2.5 micrometers. These tiny particles can get deep into your lungs and even your bloodstream.
- VOCs: Volatile Organic Compounds are gases emitted from solids or liquids. A high reading often points to chemical pollutants from cleaning supplies or furniture. Find out more about the sources of VOCs in your home.
- CO_2: Carbon dioxide is what we exhale. High CO_2 levels aren’t directly toxic in most homes, but they are a critical indicator of poor ventilation. If CO_2 is building up, so are all the other pollutants.
For a deeper dive into choosing the right device, check out our complete IAQ monitor guide.
| Metric | Good | Moderate | Poor |
| PM_2.5 (mug/m3) | 0–12 | 13–35 | 36+ |
| CO_2 (ppm) | 400–1,000 | 1,001–2,000 | 2,001+ |
| Total VOCs (ppb) | 0–220 | 221–660 | 661+ |
(Levels are based on guidelines from the EPA, ASHRAE, and other environmental health agencies.)
How to Improve Indoor Air Quality: 3 Core Strategies
Improving your home’s air doesn’t have to be complicated. It boils down to three main approaches: ventilating, filtering, and controlling the source.
1. Ventilation: Bring in the Fresh Air
Ventilation is the process of replacing stale, polluted indoor air with fresh outdoor air. It’s the single most effective way to reduce the concentration of pollutants like CO_2 and VOCs.
- Open Windows: The simplest method. Open windows on opposite sides of the house for 15 minutes a day to create a cross-breeze.
- Use Exhaust Fans: Always run the exhaust fan in your kitchen when cooking and in your bathroom when showering. This removes moisture and contaminants at the source.
- Circulate Air: Use ceiling or portable fans to keep air from becoming stagnant.
2. Filtration: Capture the Pollutants
Filtration involves using a device to physically remove particles from the air.
- Upgrade Your HVAC Filter: Your central air system is a whole-house air filter. Switch from cheap fiberglass filters to pleated ones with a MERV rating of 11 to 13. This captures much smaller particles like pet dander, pollen, and some bacteria. Wondering about IAQ and air conditioning? A good filter is key.
- Use a Portable Air Purifier: For targeted cleaning in bedrooms or living areas, a high-quality air purifier with a HEPA filter is your best bet. HEPA filters are certified to capture 99.97% of particles down to 0.3 microns. To know if your unit is working, see our guide on air purifier effectiveness.
3. Source Control: Stop Pollution Before It Starts
The easiest way to deal with a pollutant is to remove its source from your home entirely.
- Choose Low-VOC Products: When painting or buying new furniture, look for products labeled “low-VOC” or “zero-VOC.”
- Rethink “Clean” Scents: Air fresheners, scented candles, and harsh chemical cleaners are major sources of VOCs. Opt for unscented cleaning products and natural alternatives like essential oil diffusers (used in moderation).
- Manage Pets: Groom pets regularly (ideally outside) to reduce dander. A good vacuum with a HEPA filter is also essential.
- Clean Smarter: Dust with a damp microfiber cloth instead of a dry feather duster to trap dust instead of sending it airborne.
Humidity: The Overlooked Factor in Air Quality
Humidity—the amount of water vapor in the air—plays a huge role in IAQ. The goal is to keep your home in the “Goldilocks zone.” The ideal humidity level is between 40% and 60%.
- Too High (>60%): High humidity creates the perfect breeding ground for mold, mildew, and dust mites. It can lead to musty smells and condensation on windows.
- Too Low (<40%): Dry air can cause itchy skin, a scratchy throat, and dry sinuses, making you more susceptible to colds and infections. It can also cause wood furniture and floors to crack.
Use a hygrometer (most IAQ monitors include one) to track your humidity. A dehumidifier can solve high humidity, while a humidifier can add moisture to dry winter air.
Do You Need to Call a Professional?
For most general IAQ concerns, the DIY steps of ventilating, filtering, and controlling sources are highly effective.
When DIY is usually enough:
- You want to reduce general dust and allergens.
- Your IAQ monitor shows slightly elevated CO_2 or PM_2.5 levels.
- You want to proactively create a healthier home environment.
When to call a professional:
- You suspect you have a mold problem (e.g., you see or smell it).
- You live in a region with high radon levels and have never had your home tested.
- You suspect contamination from asbestos or lead in an older home.
- Despite your best efforts, IAQ readings remain poor or family members continue to experience symptoms.
Professionals can perform detailed testing and offer solutions like radon mitigation systems, mold remediation, or duct cleaning.
Tools & Resources
Ready to take control of your IAQ? Use these resources to get started.
- [Tool] Indoor Humidity Calculator: Find out if you need to add or remove moisture.
- [Tool] What’s My IAQ Score? Quiz: Answer a few questions to get a baseline score for your home’s air health.
- [Checklist] Healthy Home IAQ Checklist (Printable): A room-by-room guide to improving your air quality.
Frequently Asked Questions (FAQs)
Good indoor air quality means the air inside your home is free from harmful levels of pollutants like PM_2.5, VOCs, and radon. It’s also properly ventilated (indicated by CO_2 levels under 1,000 ppm) and has a comfortable humidity level between 40% and 60%.
The most reliable way is with an electronic indoor air quality monitor. These devices measure key pollutants like PM_2.5, VOCs, and CO_2 in real time, giving you actionable data about your environment.
Physical symptoms like frequent headaches, fatigue, irritated eyes, coughing, and worsened allergies can be signs. Environmental signs include musty odors, visible mold growth, excessive dust, and high humidity or condensation.
Open your windows daily for ventilation, use exhaust fans when cooking or showering, clean with natural products like vinegar and water, and dust with damp cloths. Reducing synthetic fragrances also helps.
While plants do absorb some pollutants, the famous NASA study was conducted in a small, sealed chamber. In a real home with normal air exchange, you would need a huge number of plants to have a significant filtering effect. They are great for well-being but are not a substitute for proper ventilation and filtration.
You can still do a lot! Use a high-quality portable air purifier, open windows when you can, use kitchen and bath exhaust fans, choose low-VOC cleaning products, and manage humidity with a portable humidifier or dehumidifier.
It depends on the purifier. Most standard HEPA filters are designed for particles, not gases like VOCs. To remove VOCs, you need an air purifier with a substantial activated carbon filter in addition to a HEPA filter.
If your symptoms (like headaches, stuffy nose, or fatigue) consistently improve when you leave the house and return when you come back, it could be related to your indoor environment. This is sometimes referred to as Sick Building Syndrome. Tracking your symptoms alongside IAQ monitor readings can help you find a connection.
It can be bad in both, but for different reasons. In winter, we seal our homes tight to conserve heat, which traps pollutants and raises CO_2 levels. In summer, humidity and pollen can be bigger issues, and some outdoor pollution like wildfire smoke can make its way indoors.
For small homes or apartments, look for a compact air purifier with a high CADR (Clean Air Delivery Rate) relative to its size. Ensure it has both a true HEPA filter for particles and an activated carbon filter for odors and VOCs.