Ventilation Filters (G4, F7, HEPA, Carbon): What Really Improves Air Quality in Los Angeles

Indoor air in Los Angeles faces a unique mix of challenges: traffic-related smog, fine dust, seasonal pollen, and—at times—wildfire smoke. A ventilation system can help, but only if the filtration stages match the pollutants you actually want to remove. Here’s what G4, F7, HEPA, and activated carbon filters really do, and when each one makes a noticeable difference. A G4 (coarse) filter is the “first line” in many systems. It captures larger particles such as lint, hair, and visible dust. While it won’t meaningfully reduce PM2.5, it protects fans and heat exchangers, keeps ducts cleaner, and extends the life of finer filters placed downstream. An F7 filter (fine filtration, often close to MERV 13) is the practical workhorse for city air. It targets smaller particles including pollen and a significant share of PM10 and PM2.5—key contributors to haze and respiratory irritation. For many LA homes, F7 offers the best balance of real-world air quality improvement and airflow. HEPA filtration goes further, trapping very small particles (including much of PM2.5 and ultrafine fractions) at high efficiency. It’s most beneficial for allergy sufferers, asthma management, and smoke events. However, HEPA creates higher resistance, so your ventilation unit must be designed for it; otherwise airflow drops and the system becomes less effective. Activated carbon (charcoal) is different: it targets gases and odors, not dust. It can reduce smells, some VOCs, and portions of smoke-related compounds, but its performance depends on carbon amount, contact time, and saturation. Carbon pairs best with F7 or HEPA: particles are captured by the mechanical filter, while carbon handles odors and gases. Best practice in Los Angeles is a staged approach: G4 prefilter + F7 for everyday use, with HEPA and/or carbon when you need maximum protection from smoke, allergies, or persistent odors. Replace filters on schedule and monitor pressure drop—clean air requires both good filtration and proper airflow.