Is Your HVAC System Working For or Against IAQ?

• Indoor concentrations of some pollutants may be 2–5 times higher than outdoor air, with most exposure occurring indoors. Major indoor pollutants—such as radon, carbon monoxide, PM2.5, and VOCs—come from everyday sources like cooking, heating, and building materials. 
• Both short-term symptoms and long-term health risks are linked to poor indoor air quality, especially for vulnerable populations.
• Effective IAQ improvement depends on a combination of source control, proper ventilation, and high-efficiency filtration.
• Monitoring indoor air and maintaining HVAC systems helps ensure that improvements are measurable and sustained over time.

 

Indoor air may be more polluted than you think. In fact, indoor environments can sometimes be more polluted than outdoors, according to the U.S. Environmental Protection Agency (EPA).^[1] The European Environment Agency (EEA) also notes that Europeans spend much of their time indoors, where exposure to pollutants from heating, cooking, cleaning products, building materials, and poor ventilation can significantly affect health.^[2] Everyday sources,  including gas stoves, cleaning products, and building materials, continuously release pollutants into the spaces where you live, work, and rest, and because most people spend roughly 90% of their time indoors, that exposure builds quickly over time.^[1][2][3] 

Understanding what affects your indoor air is the first step toward improving it, and this guide outlines the key pollutants, their health effects, and practical steps you can take to create a cleaner, healthier indoor environment. Throughout this guide, commonly used IAQ guidance from the U.S. (EPA/ASHRAE) and Europe (EU/EEA/BUILD UP) is referenced as representative examples. Actual requirements, standards, and test methods may vary by country and region. 

[1] https://www.epa.gov/report-environment/indoor-air-quality
[2] https://build-up.ec.europa.eu/en/resources-and-tools/articles/acceptable-indoor-environmental-quality-and-energy-efficiency
[3] https://www.epa.gov/air-research/indoor-air-quality-exposure-and-characterization-research 

HVAC systems influence IAQ through three main functions: ventilation, filtration, and ongoing operation and maintenance. When these factors work together, they can help reduce pollutant buildup, capture airborne particles, and keep system performance consistent over time.

Ventilation
Ventilation helps reduce indoor pollutant concentrations by bringing outdoor air into the space and diluting contaminants generated indoors. Across major IAQ guidance, ventilation is consistently recommended alongside source control and filtration to reduce indoor pollutant buildup. For example, the EPA identifies ventilation as a main strategy for improving IAQ, and ASHRAE Standards 62.1 and 62.2 define ventilation system design and minimum ventilation rates for acceptable indoor air quality. European guidance also highlights the same core approach, with CO₂ often used as an indicator of air exchange.^[1]

Filtration
Filtration supports IAQ by capturing airborne particles as air moves through HVAC equipment or dedicated air-cleaning devices. European Commission guidance notes that air filtration is required to help control particulate matter from outdoor sources, while indoor particulate matter is managed through source reduction and adequate ventilation. In the U.S., EPA guidance explains that MERV ratings indicate how effectively HVAC filters capture particles between 0.3 and 10 microns, making filter selection an important part of IAQ planning.^[2] Filter classifications differ by region, including MERV in the U.S. and ISO 16890 in many European markets, but both systems are intended to indicate how effectively filters capture airborne particles. 

Operation & Maintenance
Operation and maintenance help ensure that ventilation and filtration continue performing as intended. The U.S. Department of Energy notes that clogged filters reduce airflow and system efficiency, while European guidance connects IAQ management with proper ventilation rates, filtration, and monitoring. Regular filter replacement, airflow checks, and system inspections help maintain the conditions needed for consistent IAQ performance.^[3]

[1] https://www.epa.gov/indoor-air-quality-iaq/improving-indoor-air-quality
[2] https://www.epa.gov/indoor-air-quality-iaq/what-merv-rating 
[3] https://build-up.ec.europa.eu/en/resources-and-tools/articles/acceptable-indoor-environmental-quality-and-energy-efficiency 

Indoor air quality is shaped by a combination of pollutants that often originate from common sources we encounter every day. While these contaminants vary in form and impact, several stand out due to their consistent presence and health risks.  

Poor indoor air quality can affect comfort, health, and daily performance, with symptoms that may appear quickly or develop over time.

• Short-term effects: Irritation, headaches, dizziness, fatigue, and asthma symptoms can occur after indoor pollutant exposure.
• Long-term effects: PM2.5 exposure is linked to cardiovascular and respiratory disease, while radon exposure is linked to lung cancer risk.^[1][2]
• Higher-risk groups: Air pollution can pose greater risks for children and pregnant women, including possible impacts on birth outcomes.^[1][3]

As reference points, health agencies such as the U.S. EPA provide guidance levels for key pollutants. Carbon monoxide guidance levels are 4 mg/m³, or approximately 3.5 ppm, on a 24-hour average under the WHO 2021 air quality guidelines^[4]. As a reference point, in 2024, the US EPA finalized a revised annual PM2.5 National Ambient Air Quality Standard (NAAQS)* of 9.0 µg/m³; however, this standard is subject to ongoing regulatory review and may be revised.** ^[2][5][6] These reference points reinforce the importance of reducing sources, improving ventilation, and monitoring indoor air quality over time.

*The NAAQS applies to outdoor ambient air; it is often referenced as a benchmark for evaluating indoor particulate levels. Always verify the latest applicable standards for your region.

**Readers should verify the current applicable standard at the time of reading.

[1] https://www.who.int/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health 
[2] https://www.epa.gov/radon/what-epas-action-level-radon-and-what-does-it-mean
[3] https://stacks.cdc.gov/view/cdc/225899
[4] https://www.who.int/teams/environment-climate-change-and-health/air-quality-and-health/health-impacts/types-of-pollutants
[5] https://www.epa.gov/indoor-air-quality-iaq/what-average-level-carbon-monoxide-homes
[6] https://www.epa.gov/pm-pollution/national-ambient-air-quality-standards-naaqs-pm

Reducing harsh indoor sources is important, but clean air also depends on how well air moves through the home. EPA identifies improved ventilation as one of the three basic strategies for improving indoor air quality, alongside source control and filtration. The European Commission’s BUILD UP platform provides similar guidance, stating that good indoor air quality depends on source control, effective ventilation, and filtration of external pollutants. Increasing outdoor air can help lower indoor pollutant concentrations, and ASHRAE recommends a minimum residential ventilation rate of 0.35 air changes per hour, but not less than 15 cfm per person. Equivalent ventilation targets and calculation methods may differ by country and building codes, so use local standards for final design. ^[1][2][3]

Natural ventilation can help improve airflow, but it also has limitations. Modern buildings are increasingly airtight, making natural airflow less effective, while opening windows can introduce outdoor pollutants such as PM2.5, pollen, and dust, depending on seasonal and environmental conditions.

• Use windows and doors when weather and outdoor air quality allow.^[2] 
• Run kitchen and bathroom exhaust fans that vent outdoors.^[2]
• Consider mechanical ventilation in tighter spaces where natural airflow is limited.^[1][2]

As we've established, ventilation and filtration are important components of IAQ management. The following solution sections from LG's ETV and filtration technologies are designed to support ventilation and filtration functions—not to prevent, treat, or cure any specific health condition.

LG’s ERV solutions are designed around this ventilation-focused approach by continuously supplying outdoor air while exhausting indoor air through heat exchange technology that helps reduce heating and cooling energy loss during ventilation.

In residential environments, LG Residential ERV systems are designed to support cleaner indoor air, energy-efficient ventilation, and easier system management in increasingly airtight homes. For cleaner air, the system combines ISO 16890 ePM1 95% filtration, dual PM1.0 and CO₂ monitoring, UVnano™ pre-filter treatment*, and antibacterial and mold-resistant air passages to help manage fine dust, airborne contaminants, and indoor air conditions.

*UVnano™ effectiveness is limited to the pre-filter surface area directly exposed to UVC light. 

Improving indoor air quality comes down to consistent habits that address the main sources covered in this article. These eight actions are practical starting points for reducing exposure and keeping indoor air easier to manage.

1. Test your home for radon, since EPA states that testing is the only way to know your level of exposure.^[1]
2. Install carbon monoxide alarms on each level of the home and outside sleeping areas.^[2] 
3. Keep indoor spaces smoke-free, as the WHO states, there is no safe level of secondhand smoke exposure.^[3]
4. Consider mechanical ventilation or ERV systems to help provide more consistent airflow and indoor air management in increasingly airtight spaces.^[4]
5. Replace or clean HVAC filters according to manufacturer or contractor guidance.^[5]
6. Use portable air cleaners or upgraded HVAC filters as supplements to source control and ventilation.^[6]
7. Choose EPA Safer Choice- or EU Ecolabel-certified products to reduce pollution at the source through safer ingredients.^[7][8]
8. Use indoor air monitors carefully to track specific pollutants, while recognizing they do not provide a complete picture of indoor air quality.^[9]

[1] https://www.epa.gov/radon
[2] https://www.cpsc.gov/Safety-Education/Safety-Education-Centers/Carbon-Monoxide-Information-Center/CO-Alarms
[3] https://www.who.int/news/item/29-05-2007-only-100-smoke-free-environments-adequately-protect-from-dangers-of-second-hand-smoke
[4] https://www.epa.gov/indoor-air-quality-iaq/improving-indoor-air-quality
[5] https://www.energy.gov/energysaver/air-conditioner-maintenance
[6] https://www.epa.gov/indoor-air-quality-iaq/guide-air-cleaners-home
[7] https://www.epa.gov/saferchoice
[8] https://environment.ec.europa.eu/topics/circular-economy-topics/eu-ecolabel_en
[9] https://www.epa.gov/indoor-air-quality-iaq/low-cost-air-pollution-monitors-and-indoor-air-quality 

Indoor air quality is shaped by how effectively pollutants are controlled, filtered, and ventilated within increasingly airtight indoor environments. As this article has outlined, ventilation plays a central role in IAQ management by helping reduce indoor pollutant buildup while supporting more consistent airflow and indoor comfort.

Mechanical ventilation and ERV systems can further support this process by supplying fresh outdoor air while helping reduce the energy loss often associated with ventilation. Combined with appropriate filtration, monitoring, and ongoing HVAC maintenance, these approaches can help create cleaner, more consistent indoor environments over time.