How to Keep Indoor Air Clean in Summer from Smog and Pollen

Summer in Southern California can be tough on indoor air quality. Smog, drifting pollen, and even wildfire smoke can slip inside and aggravate allergies, asthma, headaches, and fatigue. The good news: a few evidence-based steps—paired with the right HVAC setup—can greatly reduce particulate matter and allergens while keeping energy use reasonable.

Why summer makes indoor air worse

On hot days, ground-level ozone and fine particles (PM2.5) from traffic and industry typically climb, especially across the Los Angeles Basin. Pollen from grasses, trees, and weeds peaks in waves. In some years, wildfire smoke adds ultrafine particles that travel far. Homes in Los Angeles County and nearby areas, including Orange County, Ventura County, and Western Riverside County, often experience pressure imbalances and infiltration that pull that air inside.

Step-by-step: cleaner air without guesswork

1) Start with filtration—use the right filter, not the thickest

• Upgrade to a high-quality pleated filter rated MERV 11–13 if your system supports it. This range captures much of the pollen and a significant portion of smoke particles.
• Check system compatibility. Higher MERV filters raise static pressure; if your blower and ductwork aren’t sized for it, you can reduce airflow, ice the coil, and increase energy use. This is a common DIY mistake.
• HEPA options: true HEPA is highly effective but often requires a dedicated bypass cabinet or properly sized portable units. Avoid “HEPA-like” marketing claims—look for CADR ratings for smoke and pollen.
• Replace filters on schedule. During heavy smog or wildfire periods, expect shorter lifespans.

2) Ventilate smartly—bring in air when it’s clean, seal when it’s not

• Watch the AQI. On high-smog or high-pollen days, keep windows closed, use recirculation, and filter indoor air. When AQI improves (often early mornings or after coastal breezes), ventilate to dilute indoor pollutants.
• Balanced ventilation (ERV/HRV) with a MERV-rated intake filter can supply fresh air without large pressure swings. In hot, dry spells an ERV helps manage sensible load; near the coast, it helps limit humidity swing.
• Exhaust fans are essential, but constant exhaust without makeup air can create negative pressure and pull in unfiltered air through cracks. A qualified specialist can balance flows.

3) Optimize AC operation for IAQ

• Address short cycling. Proper sizing and airflow ensure longer, steadier runs that improve filtration and dehumidification.
• Consider low-speed continuous fan circulation during severe pollen events, paired with an efficient filter. If your ducts leak or the coil is dirty, continuous fan can backfire—maintenance first.
• Keep coils and condensate drains clean to prevent biofilm and musty odors. UV-C at the coil (non-ozone systems) can help manage microbial growth.

4) Control indoor sources and habits

• Make an entryway “airlock”: outdoor mats, shoe removal, and a quick clothes change after yard work reduce pollen loading indoors.
• Vacuum with a sealed HEPA vacuum; dust with a damp microfiber cloth so allergens don’t resuspend.
• Wash bedding in hot water weekly; bathe pets more frequently during pollen peaks and brush them outdoors.
• Avoid burning candles and incense on bad AQI days; choose electric alternatives.

5) Manage humidity to support lungs and filters

• Target 40–50% RH. Too dry and airways become irritated; too humid and dust mites and mold thrive.
• In coastal zones, consider a whole-home dehumidifier for peak humidity; inland, AC usually controls RH if airflow and sizing are correct.

6) Prepare for wildfire smoke days

• Set HVAC to recirculate, close windows and fireplace dampers, and run high-efficiency filtration continuously.
• Use sealed-room HEPA purifiers in sleep areas. Check door sweeps and weatherstripping to reduce infiltration.

7) Use data to guide decisions

• Place a PM2.5 monitor indoors and compare with outdoor AQI to time ventilation. A CO2 monitor helps gauge when fresh air is needed without over-ventilating during smog peaks.

What not to do

• Don’t oversize the AC “for extra cooling.” Oversizing worsens humidity control and filtration time.
• Be cautious with ionizers and ozone-generating gadgets. Ozone is a lung irritant and can react with indoor chemicals to form more pollutants.
• Avoid stacking multiple dense filters without confirming blower capacity and duct static—it can damage equipment.

When a professional is essential

High-MERV retrofits, HEPA bypass units, UV-C installation, ERV/HRV design, duct sealing, and airflow balancing require load calculations, static-pressure measurements, and commissioning. Refrigerant handling and electrical work involve safety and code compliance. In many cases—especially after smoke exposure, water damage, or during insurance claims—insurers expect documentation from a qualified specialist. Attempting complex changes without proper design can void warranties, reduce efficiency, and create safety hazards.

Who we are

#1 AC Guys is a family HVAC business serving Los Angeles County and nearby areas, including Orange County, Ventura County, and Western Riverside County. Our mission is simple: healthy air at home for healthy life. We handle residential and commercial systems, with a focus on large and complex projects.

We are a fourth-generation family of engineers with 80+ years of engineering experience. Our engineers trained at the manufacturers’ facilities of Fujitsu (Japan), Mitsubishi Electric (Thailand), Midea (China), Gree (China), and Haier (China). That foundation helps us integrate filtration, ventilation, and cooling so your system delivers comfort and cleaner indoor air during peak summer smog and pollen seasons.

Service area examples

We work across the region, including cities like Los Angeles, Long Beach, Pasadena, Glendale, Burbank, Santa Monica, Anaheim, Irvine, Santa Ana, Costa Mesa, Newport Beach, Huntington Beach, Oxnard, Ventura, Thousand Oaks, Simi Valley, Riverside (western), and Corona.

Quick checklist for cleaner air this summer

1. Use MERV 11–13 filtration if your system supports it; change filters more often during smoke or pollen spikes.
2. Ventilate based on AQI; seal up and recirculate when outdoor air is poor.
3. Control humidity around 40–50% RH.
4. Keep coils, drains, and ducts clean; address leaks and pressure imbalances.
5. Deploy room HEPA units for bedrooms and home offices.
6. Adopt entryway and cleaning habits that cut dust and pollen at the source.
7. Consult qualified professionals for system changes and commissioning to satisfy codes, warranties, and insurance requirements.

Clean indoor air in summer isn’t about a single gadget. It’s a system—filtration, ventilation, humidity, and airflow—designed and maintained to work together. With smart habits and a correctly engineered HVAC setup, you can breathe easier all season.