How Summer Affects Indoor Air Quality in Southern California Homes

Summer in Anaheim, CA brings beautiful weather, sunshine, warm temperatures, and dry conditions perfect for beach days or long walks outside. However, this same weather also contributes to seasonal air quality concerns, particularly with higher levels of pollen and the potential for wildfire smoke.

If you’re heading indoors to escape outdoor pollution, it’s important to remember that your indoor air isn’t automatically cleaner. In fact, according to the EPA, indoor air is often two to five times more polluted than the air outside.

Common Causes of Poor Indoor Air Quality

You close the windows during hot summer days to keep the heat out and cooling costs down. However, that means less ventilation. Without fresh air circulating, pollutants can build up quickly inside your home, affecting your family’s comfort and health.

Common Indoor Pollutants and Allergens

Indoor air can contain a mixture of particles and allergens that accumulate over time. When you go outside, pollen can cling to shoes, clothing, or pet fur and easily make its way inside. Dust, pet dander, dust mites, and mold spores are also common indoor allergens. This is especially true in homes with carpeting, older ductwork, or high humidity issues. For family members with allergies, asthma, or respiratory sensitivities, these particles may worsen symptoms.

Pathogens can also circulate through your HVAC system. If air filters aren’t capturing these pollutants effectively, they can continue to recirculate and may lead to the spread of seasonal illness.

Off-Gassing from Household Products

Volatile organic compounds (VOCs) are invisible pollutants off-gassed from many everyday items. New flooring, cabinets, mattresses, and even paint can emit VOCs into the air. Cleaning products and air fresheners are another major source, especially those with synthetic fragrances. Warmer weather in summer can cause these chemicals to be released more quickly, making the air even more polluted.

If you have recently completed a renovation or brought new furniture into the home, your VOC levels may be higher than normal. This may be a bigger issue in homes with limited ventilation.

Ozone and Poor Ventilation

Ozone is often seen as an outdoor concern, but it can affect your house too, especially in areas like Southern California, where high outdoor ozone levels are common in summer. Homes or older buildings with poorly sealed windows or inadequate ventilation systems may allow outdoor ozone and smog to seep inside. Once indoors, these pollutants can linger and affect your health over time.

Wildfire Smoke

Southern California is no stranger to summer wildfires. Even if you live miles from an active fire, smoke can travel far and enter your home through small cracks, window gaps, or your HVAC system if it is not equipped with a proper filtration setup. Wildfire smoke increases the concentration of fine particulate matter in the air, which can aggravate breathing issues and cause symptoms like throat irritation, coughing, and eye discomfort. Cheap air filters may not trap these particulates, and instead allow them to accumulate in your home.

Issues With Indoor Humidity

The relative humidity in your home should be between 35% and 50%. While your air conditioner removes moisture when it runs, it may not be enough to keep indoor humidity within the ideal range. Additionally, indoor activities such as cooking, cleaning, and bathing can contribute to high humidity.

This can promote the growth of mold and make your home feel stuffy and warm. Humid air can also retain more particulate matter than dry air, potentially exacerbating allergies, asthma, and other respiratory symptoms.

Addressing Indoor Air Quality During the Summer

There are several ways to improve your indoor air quality during the summer so you can stay comfortable and healthy. Even on mild days, it helps to run your cooling system. On cooler days, you can turn your thermostat to “circulate” or “fan only” to keep air moving and filter out particles. The filter in your HVAC system traps larger contaminants before they can recirculate throughout your living space.

You can also have our team install a whole-house air filtration system that integrates seamlessly with your HVAC system. These systems offer advanced filtration, removing up to 99.97% of airborne particles. The specific contaminants removed will depend on the type of filter you choose. Many units use high-efficiency particulate air (HEPA) filters, which can capture bacteria, mold spores, and other microscopic particles. Activated carbon filters are another option. They target VOCs and gases and help eliminate unpleasant odors from your indoor air.

Humidity control equipment also goes a long way toward improving air quality. Not only does proper humidity promote comfort, but it prevents mildew and mold, and reduces the number of water molecules in the air that contaminants can hitch rides on.

Also, consider upgrading the filter in your HVAC system. Filters are rated using the MERV scale (Minimum Efficiency Reporting Value), which measures their ability to trap particles. The higher the rating, the more airborne contaminants it captures. Most residential systems can support a filter with a MERV rating between 8 and 13, offering a good balance between airflow and filtration.

Additionally, be sure to follow the recommended replacement schedule, typically every 30 to 90 days, to keep your system running efficiently. Many homeowners check their filters once a month to ensure they know when it’s time for a replacement. You may have to change yours out more frequently when there is an active wildfire or pollen counts are high.

Air Conditioning and Ventilation System Maintenance

Your home’s air conditioning and ventilation systems play a crucial role in managing indoor air quality, but only when properly maintained. Without regular inspections, these systems can become inefficient or even harmful, circulating dust, mold spores, or bacteria throughout your home.

Schedule professional maintenance at least once a year to ensure components, such as coils, condensate lines, and ductwork, are clean and functioning properly. A neglected system not only reduces air quality but can also increase your monthly utility bills.

If your HVAC system is more than 10–15 years old, it might be time to consider an upgrade. Newer systems are more energy-efficient and often come equipped with advanced filtration and humidity controls that support healthier indoor environments.

Other Steps to Improve Indoor Air Quality

Everyday activities like cooking, cleaning, and running appliances can introduce particulate matter, excess humidity, and volatile organic compounds (VOCs) into your home. Proper ventilation helps reduce these pollutants. Using the fan in your range hood while cooking can minimize grease, smoke, and moisture. Bathroom exhaust fans are essential for managing humidity and preventing mold growth. These small habits support your HVAC system in keeping the air cleaner.

The products you bring into your home also play a role. Choosing low-VOC or natural cleaners, avoiding synthetic air fresheners, and allowing new carpets or furniture to off-gas outdoors before installation can significantly reduce chemical buildup indoors.

If someone in your household suffers from allergies or asthma, regular cleaning is especially important. Vacuum frequently with a HEPA-filtered vacuum and groom pets often to limit dander and other allergens from circulating through your living space.

Contact Your Local HVAC Professionals

At Associated Heating & Air, we’re committed to helping Anaheim, CA homeowners create healthier, more comfortable indoor air. Whether you need help selecting a new cooling system, scheduling routine maintenance, or addressing repairs, our experienced technicians are here to assist. Contact us today to schedule an appointment and take the next step toward cleaner indoor air.