How to Improve Indoor Air Quality

Common Indoor Pollutants

Understanding what pollutes your indoor air is the first step toward improving it. Indoor air quality is affected by a different mix of pollutants than outdoor air:

Particulate Matter (PM2.5 and PM10)

Fine particles can enter homes from outdoor sources or be generated indoors through:

• Cooking, especially frying and grilling
• Burning candles, incense, or wood
• Smoking or vaping
• Vacuuming without HEPA filters
• Dust and pet dander
• Outdoor pollution infiltrating through windows, doors, and HVAC systems

Volatile Organic Compounds (VOCs)

VOCs are gases emitted from thousands of common household products:

• Paints, stains, and varnishes
• Cleaning products and disinfectants
• Air fresheners and scented products
• New furniture and carpet (off-gassing)
• Personal care products (perfume, hairspray)
• Craft supplies and adhesives
• Dry-cleaned clothing

Combustion Pollutants

• Carbon monoxide (CO): From gas stoves, heaters, fireplaces, and attached garages
• Nitrogen dioxide (NO2): Primarily from gas stoves and unvented heaters
• Secondhand smoke: Contains over 7,000 chemicals including 70 known carcinogens

Biological Contaminants

• Mold and mildew: Thrive in damp areas like bathrooms, basements, and around leaks
• Dust mites: Live in bedding, upholstery, and carpeting
• Pet dander: Microscopic skin particles from cats, dogs, and other pets
• Pollen: Enters through windows, doors, and on clothing
• Bacteria and viruses: Spread through air and surfaces

Other Indoor Pollutants

• Radon: A radioactive gas that enters from soil beneath buildings (second leading cause of lung cancer)
• Formaldehyde: Off-gases from pressed wood products, insulation, and textiles
• Asbestos: Found in older building materials and insulation
• Lead dust: From deteriorating lead paint in older homes

The Importance of Ventilation

Proper ventilation is fundamental to good indoor air quality. It dilutes indoor pollutants by bringing in fresh outdoor air and removing stale, polluted indoor air.

Types of Ventilation

Mechanical Ventilation

• Exhaust fans: Kitchen and bathroom fans remove pollutants at the source. Always use exhaust fans while cooking and for 20-30 minutes after showering.
• Whole-house fans: Pull air through the house and exhaust it through the attic, providing rapid air exchange on mild days.
• Supply ventilation: Brings filtered outdoor air directly into the home through fans and ducts.
• Balanced ventilation: Combines supply and exhaust systems for controlled air exchange.
• Energy Recovery Ventilators (ERVs): Exchange indoor and outdoor air while transferring heat and moisture, maintaining energy efficiency while providing fresh air.

When to Ventilate

• While cooking (always use range hood exhaust)
• During and after cleaning
• After using any chemical products
• When outdoor AQI is good and weather permits
• After bringing in new furniture or completing renovations
• If you notice musty odors or stuffiness

Air Purifiers Guide

Air purifiers can significantly improve indoor air quality, especially during poor outdoor air quality days when ventilation isn't practical. Here's what you need to know to choose and use them effectively.

Types of Air Purifiers

HEPA Filters (Recommended)

High-Efficiency Particulate Air (HEPA) filters are the gold standard for particle removal:

• Remove 99.97% of particles 0.3 micrometers or larger
• Effective against PM2.5, dust, pollen, mold spores, and pet dander
• No harmful byproducts produced
• Require regular filter replacement (typically every 6-12 months)

Activated Carbon Filters

• Absorb gases, odors, and VOCs
• Best used in combination with HEPA filters
• Limited capacity; must be replaced when saturated
• More carbon means more absorption capacity

UV-C Light Purifiers

• Can neutralize some bacteria and viruses
• Less effective against particles and gases
• Best as a supplement to HEPA filtration, not a replacement

Ionic and Ozone Generators (Caution)

Choosing the Right Size

Air purifiers are rated by the volume of air they can clean, measured as Clean Air Delivery Rate (CADR):

• Match the CADR to your room size; the purifier should be able to cycle all the air in the room 4-6 times per hour
• For a 200 square foot bedroom with 8-foot ceilings, you need a CADR of at least 130
• When in doubt, go larger; an oversized purifier running on low is often quieter and more effective
• For open floor plans, you may need multiple units or a whole-house system

Air Purifier Placement

• Place in rooms where you spend the most time (bedrooms, living areas)
• Position away from walls and furniture for optimal airflow
• Avoid placing near doors and windows where outdoor air enters
• Keep the unit running continuously on low; intermittent use is less effective

Houseplants That Help

While houseplants alone cannot replace mechanical air filtration, certain plants can contribute to a healthier indoor environment by absorbing some pollutants and adding humidity.

Plants with Air-Purifying Properties

Realistic Expectations

While NASA studies have shown plants can remove VOCs in laboratory conditions, real-world benefits are more modest. You would need hundreds of plants in a typical home to significantly impact air quality through plants alone. However, plants do:

• Improve psychological well-being and reduce stress
• Add humidity to dry indoor air
• Provide some level of pollutant absorption
• Create a more pleasant living environment

Reducing Pollution Sources

The most effective way to improve indoor air quality is to eliminate or reduce pollution sources. This strategy, called source control, prevents pollutants from entering the air in the first place.

Cooking

• Always use your range hood exhaust fan while cooking and for 10-15 minutes afterward
• If possible, vent your range hood to the outside rather than recirculating
• Consider using an induction cooktop instead of gas (gas stoves emit NO2, CO, and PM2.5)
• Open windows when outdoor air quality permits
• Use lids on pots to reduce particle emissions

Cleaning Products

• Choose fragrance-free and low-VOC cleaning products
• Avoid aerosol sprays; use pump bottles or wipes instead
• Make your own cleaners with simple ingredients (vinegar, baking soda, castile soap)
• Ventilate well while cleaning and for 30 minutes afterward
• Store chemicals in sealed containers, preferably in a garage or utility room

Personal Care Products

• Choose unscented or naturally scented products when possible
• Minimize use of hairsprays and aerosol products
• Apply nail polish near open windows or use a portable exhaust fan
• Let nail polish dry thoroughly before closing windows

Furnishings and Building Materials

• Choose solid wood furniture over pressed wood products (particleboard, MDF) when possible
• Look for low-VOC or zero-VOC paints and finishes
• Allow new furniture to off-gas in a garage or well-ventilated area before bringing inside
• Select carpets and flooring certified for low emissions (look for Green Label Plus or FloorScore)
• Unroll new carpets and let them air out before installation

Combustion Sources

• Never smoke indoors or allow others to smoke inside
• Limit candle and incense burning; if used, ventilate well
• Ensure all combustion appliances are properly vented
• Have gas appliances inspected annually
• Never use unvented space heaters indoors
• Install carbon monoxide detectors on every floor

Humidity Control

Maintaining proper humidity levels (between 30-50%) is crucial for indoor air quality. Both high and low humidity create problems.

High Humidity Problems (Above 50%)

• Promotes mold and mildew growth
• Creates favorable conditions for dust mites
• Can increase off-gassing from building materials
• Causes musty odors and potential structural damage

Low Humidity Problems (Below 30%)

• Dries out mucous membranes, reducing natural defense against pollutants
• Increases susceptibility to respiratory infections
• Can worsen asthma and allergy symptoms
• Causes dry skin, eyes, and throat irritation

Humidity Control Strategies

• Use dehumidifiers in damp spaces like basements and bathrooms
• Run exhaust fans during and after showers and cooking
• Fix water leaks promptly
• Ensure proper drainage around your home's foundation
• Use air conditioning during humid summer months
• In dry climates or during winter, use humidifiers to add moisture
• Monitor humidity with an inexpensive hygrometer

Cleaning Tips for Better Air Quality

Regular cleaning reduces particle pollution and allergens, but improper cleaning can temporarily worsen air quality. Follow these guidelines:

Vacuuming

• Use a vacuum with a HEPA filter to prevent particles from being released back into the air
• Vacuum at least twice weekly in high-traffic areas and rooms with carpet
• Vacuum upholstered furniture, drapes, and mattresses monthly
• Empty vacuum bags or canisters outside to prevent particle release

Dusting

• Use damp microfiber cloths that trap dust rather than spreading it
• Dust from top to bottom so particles fall to surfaces you haven't cleaned yet
• Avoid feather dusters which simply redistribute dust into the air
• Dust weekly in living areas and bedrooms

Mopping

• Damp mop hard floors after vacuuming to capture remaining particles
• Use plain water or mild, unscented cleaners
• Change mop water frequently to avoid spreading dirt

Bedding and Textiles

• Wash sheets and pillowcases weekly in hot water (130°F+) to kill dust mites
• Use allergen-proof covers on mattresses and pillows
• Wash curtains and drapes every few months
• Consider replacing carpet with hard flooring in bedrooms if you have allergies

When Outdoor Air Is Bad

During poor outdoor air quality days, your strategy shifts from ventilation to protection. Here's how to maintain good indoor air when you can't open windows:

Creating a Clean Air Refuge

1. Keep windows and doors closed: Seal any obvious gaps with weatherstripping or towels.
2. Set HVAC to recirculate: Prevent outdoor air from entering through your heating/cooling system.
3. Run air purifiers: Operate HEPA purifiers continuously in occupied rooms.
4. Upgrade HVAC filters: Use MERV 13 or higher filters in your central air system.
5. Avoid creating indoor pollution: Don't cook with high heat, light candles, or use chemical cleaners.
6. Create a clean room: Designate one room with minimal windows where you run an appropriately sized air purifier as your refuge.

During Wildfire Smoke Events

• Follow all the above steps plus seal any visible gaps around windows and doors
• If you don't have air conditioning, try to stay cool without opening windows
• Consider temporarily relocating if smoke persists and you have respiratory conditions
• Create a portable clean air kit with N95 masks and a room air purifier for emergency use

Key Takeaways