How to Improve Indoor Air Quality During Cold and Flu Season

What Is Indoor Air Quality?

Indoor air quality, often called IAQ, refers to the condition of the air inside your home. It includes airborne particles, ventilation, humidity, odors, indoor pollutants, and how well stale indoor air is replaced with fresh air.

The EPA recommends source control, improved ventilation, and air cleaning as key strategies for improving indoor air quality. During colder months, that often means reducing pollutant sources, using the ventilation equipment already in your home, replacing filters, and managing humidity carefully.

Why Indoor Air Quality Matters During Cold and Flu Season

Cold and flu season usually means more time indoors, more closed windows, and more shared air. That combination can make indoor air feel stale and allow airborne particles, odors, moisture, and other pollutants to build up.

Good ventilation cannot prevent illness on its own, but it can help reduce the concentration of airborne contaminants indoors. The CDC/NIOSH notes that ventilation improvements can increase clean air delivery and dilute potential contaminants. Bringing in outdoor air when conditions are good and exhausting stale indoor air supports better overall indoor air quality, especially when your household is spending more time inside.

What Builds Up Indoors When Homes Are Closed Up?

When windows and doors stay closed for comfort and energy savings, everyday indoor contaminants have fewer ways to leave the home. Some of the most common indoor air quality concerns during colder months include:

• Airborne respiratory particles from coughing, sneezing, talking, and normal breathing
• Moisture from showers, baths, cooking, laundry, and humidifiers
• Cooking pollutants, grease particles, smoke, and odors
• Dust, pet dander, allergens, and other airborne particles
• Volatile organic compounds from cleaning products, fragrances, paints, and household materials

Because many of these pollutants are invisible, poor indoor air quality can be easy to overlook. Common clues include lingering odors, condensation on windows, stuffy rooms, frequent dust buildup, or bathrooms that stay damp after showers.

5 Ways to Improve Indoor Air Quality During Cold and Flu Season

1. Bring More Fresh Air Into Your Home

When outdoor air quality is good, bringing in outdoor air helps dilute indoor contaminants. Opening windows can help when weather and outdoor air quality are favorable, but it is not always practical during winter, wildfire smoke events, allergy season, or extreme temperatures.

A more consistent option is a dedicated Fresh Air System. A supply fan can bring outdoor air into the home, while a balanced ventilation system such as an energy recovery ventilator can bring in fresh air while exhausting stale indoor air.

2. Run Bathroom Fans and Kitchen Ventilation Regularly

Exhaust fans are one of the simplest tools for removing stale, humid, and polluted air from your home. Run your bathroom fan during showers and baths, and let it continue running for about 20 minutes afterward or until excess humidity clears.

Kitchen ventilation matters too. Cooking can release moisture, odors, fine particles, and other pollutants into the air. Using an externally vented range hood while cooking helps remove those contaminants closer to the source.

Today’s bathroom exhaust fans can be quiet and energy efficient, making them easier to use consistently. Some ventilation products also offer additional features designed to support a cleaner bathroom environment.

For example, SurfaceShield™ bathroom exhaust fans include an antimicrobial violet light designed to help inhibit the growth of bacteria, mold, and mildew on treated surfaces. While this technology does not clean the air or replace proper ventilation, routine cleaning, or other healthy home practices, it can provide an additional layer of protection for frequently used bathroom surfaces.

3. Replace and Clean Filters

Check your HVAC filter every 1 to 3 months and replace it according to the manufacturer’s recommendation. A clean filter helps your heating and cooling system operate properly while capturing particles based on the filter’s rated performance.

Filters in other ventilation equipment matter too. Clean range hood filters, check fresh air system filters, and remove dust from bathroom fan covers so air can move freely. If your bathroom fan cover is stained, dusty, or outdated, you may be able to refresh it with a new cover rather than replacing the entire fan. Learn more in our Bathroom Fan Cover Replacement Guide: Easy Upgrades Without Renovations.

4. Keep Air Moving Through the Home

Air circulation helps reduce stale zones where contaminants and odors can linger. Many HVAC systems allow the air handler fan to run for a minimum number of minutes each hour. Using that feature can help distribute air more evenly throughout the home.

Ceiling fans, open interior doors, and properly sized ventilation equipment can also support better airflow. The goal is not to create drafts. It is to avoid trapped, stagnant air in the rooms your family uses most.

5. Upgrade Older Ventilation Equipment

If your bathroom fans are noisy, weak, or rarely used, an upgrade can make a meaningful difference. Quiet, energy-efficient fans are easier to run consistently, and models with humidity sensors can help remove moisture automatically.

Some ventilation products also include antimicrobial lighting technologies designed to help inhibit the growth of bacteria, mold, and mildew on treated surfaces. These features can complement good ventilation and regular cleaning, but they do not replace fresh air, source control, or routine maintenance.

For a broader IAQ plan, read 4 Ways to Improve Indoor Air Quality at Home.

Use Humidifiers Carefully and Control Indoor Humidity

Cold weather can make indoor air feel dry, especially when heating systems are running. A humidifier can help improve comfort in some homes, but too much humidity can create new indoor air quality problems.

The EPA recommends keeping indoor humidity below 60%, and ideally between 30% and 50%. Humidity that is too high can contribute to condensation, musty odors, mold-friendly conditions, and dust mite growth. Humidity that is too low can make the air feel dry and uncomfortable.

Use a humidity gauge to monitor your home, clean humidifiers according to the manufacturer’s instructions, and avoid over-humidifying rooms. If you see condensation on windows or notice musty smells, indoor humidity may be too high.

Cold and Flu Season Indoor Air Quality Checklist

Indoor Air Quality Step	How It Helps During Cold and Flu Season
Bring in fresh outdoor air when outdoor conditions are good	Dilutes stale indoor air and airborne contaminants.
Run bathroom exhaust fans	Removes excess humidity that can contribute to condensation, musty odors, and mold-friendly conditions.
Use kitchen ventilation	Captures cooking odors, moisture, grease particles, and pollutants near the source.
Replace HVAC filters	Helps the HVAC system move air properly while capturing particles according to filter rating.
Increase air circulation	Helps reduce stagnant air and keeps conditioned air moving through occupied rooms.
Control indoor humidity	Helps reduce overly dry air while avoiding excess moisture, condensation, and mold-friendly conditions.
Upgrade outdated fans	Quieter, more efficient ventilation equipment is easier to use consistently.

Good indoor air quality is important all year, but it becomes especially valuable during colder months when homes are closed up and families spend more time indoors. Small improvements to ventilation, filtration, humidity control, and airflow can help your home feel fresher, cleaner, and more comfortable.

For more guidance, explore Air Purification vs Ventilation: What’s the Difference? and Bathroom Air Quality Tips: Reducing Odors, Humidity and Airborne Contaminants.

Frequently Asked Questions

Does ventilation help during cold and flu season?

Yes. Ventilation helps dilute indoor air contaminants by bringing in fresh outdoor air and exhausting stale indoor air. It does not eliminate the risk of illness, but it supports healthier indoor air quality.

Can ventilation spread viruses?

Poor airflow patterns can move air from one area to another, but proper ventilation generally helps dilute airborne contaminants by replacing stale indoor air with cleaner outdoor air. Ventilation works best when paired with source control, filtration, cleaning, and other healthy home practices.

Should I open windows in winter to improve indoor air quality?

Opening windows can help when weather and outdoor air quality are safe, but it is not always practical. A dedicated fresh air system can provide more consistent ventilation without relying on open windows.

What indoor humidity is best during winter?

The EPA recommends keeping indoor humidity between 30% and 50%. In winter, the right level may depend on outdoor temperature, home insulation, and condensation risk. If windows fog or surfaces feel damp, indoor humidity may be too high.

How long should I run my bathroom fan after a shower?

Run the fan during the shower and for about 20 minutes afterward, or until excess humidity clears. The exact time depends on room size, fan performance, and moisture levels.

Can an HVAC filter improve indoor air quality?

Yes. A clean HVAC filter can help capture airborne particles based on its rating, but it should be changed regularly. Filtration works best when paired with proper ventilation and source control.

What is the best way to reduce stale air in a closed-up home?

The best approach is to combine fresh air ventilation, exhaust fans, clean filters, humidity control, and steady air circulation. This helps dilute contaminants, remove humidity, and reduce stagnant air.

Do air purifiers replace ventilation?

No. Air purifiers can help reduce certain particles from indoor air, but they do not bring in fresh outdoor air or remove moisture and gases the same way ventilation does. Both strategies can work together.