How to Improve Indoor Air Quality for Better Lung Health

Learning how to improve indoor air quality is one of the highest-impact changes you can make for your respiratory health — and one of the most overlooked. Most people assume that outdoor air is more polluted than indoor air, but research from the US Environmental Protection Agency consistently finds that indoor air is 2–5 times more polluted than outdoor air in most homes. Given that most adults spend 90% of their time indoors, improving indoor air quality is a direct investment in daily lung health.

The Main Sources of Indoor Air Pollution

• VOCs (Volatile Organic Compounds): Off-gassing from paints, carpets, composite wood furniture (MDF, particleboard), adhesives, and synthetic fabrics. VOCs include formaldehyde and benzene — both respiratory irritants and carcinogens at chronic low-level exposure.
• Combustion products: Gas cooking produces nitrogen dioxide (NO₂) and particulate matter in concentrations frequently exceeding outdoor air quality standards.
• Mould and damp: Airborne mould spores are potent respiratory triggers — a direct cause of asthma exacerbations and allergic rhinitis in sensitive individuals.
• Dust mites and pet dander: Both significant allergens. Dust mites live in bedding, soft furnishings, and carpets.
• Cleaning products and fragrances: Many conventional cleaning products release VOCs. Air fresheners, scented candles, and plug-in diffusers are among the worst offenders.
• Radon: A naturally occurring radioactive gas — the second leading cause of lung cancer in the UK after smoking.

Step 1: Measure Your Indoor Air Quality First

Before investing in solutions, measuring your baseline is worthwhile. Modern indoor air quality monitors measure PM2.5, VOCs, CO₂, humidity, and temperature in real time — and often reveal surprising findings. Cooking without ventilation can spike PM2.5 to levels exceeding heavily polluted outdoor air within minutes.

Step 2: Ventilate — The Most Important Action

Ventilation is the single most effective way to improve indoor air quality. Open windows for at least 15–30 minutes morning and evening, ideally on opposite sides of the home to create cross-ventilation. Always use an extractor fan when cooking — particularly on a gas hob. Don't dry laundry indoors without ventilation — a single load can raise indoor humidity by 30%.

Step 3: HEPA Air Purifier — Particularly for the Bedroom

A quality HEPA air purifier is the most impactful single appliance purchase for respiratory health. True HEPA filters capture 99.97% of particles 0.3 microns and larger — including PM2.5, dust mites, mould spores, pet dander, and most bacteria and viruses. Prioritise the bedroom, where you spend 7–9 hours every night breathing from a single, contained space.

Step 4: Eliminate Pollution Sources

• Switch to fragrance-free, plant-based cleaning products
• Remove scented candles, plug-in air fresheners, and synthetic room sprays
• Use water-based paints and low-VOC finishes for decorating
• Remove shoes at the door — shoes track in outdoor particulates, pesticides, and heavy metals

Step 5: Control Humidity — 40–60% Is the Target

Below 40%: dried airway mucosa, increased respiratory infection susceptibility, increased airborne virus survival time. Above 60%: mould growth, increased dust mite population, worsened respiratory symptoms. A basic hygrometer (£10–20) lets you monitor humidity continuously. A dehumidifier addresses high humidity; a cool-mist humidifier addresses very dry air in winter.

Step 6: Address Mould Promptly and Completely

Small surface mould patches (under 1m²) can be addressed with appropriate cleaning products and improved ventilation. Larger areas or mould that keeps returning after surface treatment indicates a structural moisture issue — treating the symptom without addressing the cause is futile and the mould will return.

Step 7: Test for Radon

Radon testing costs £30–50 for a 3-month test kit. If your result exceeds 200 Bq/m³, professional radon mitigation is recommended and highly cost-effective given the lung cancer risk reduction it delivers.

For the wider picture of environmental and lifestyle factors affecting your lungs, see our complete guide to natural lung health. If you're concerned about whether symptoms you're experiencing might indicate compromised lung function, see signs your lungs are not working properly.