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Protecting Indoor Air Quality from Wildfire Smoke with HVAC Best Practices

Reading time: 3 minutes

May 29

Wildfires are becoming an increasingly common and severe threat across North America, affecting regions from California to British Columbia. Beyond the immediate danger of flames, wildfire smoke poses a significant risk to indoor air quality (IAQ), impacting both residential and commercial spaces. As HVAC professionals and informed homeowners, understanding how to mitigate these risks is important for health and comfort. 

Understanding the Threat: Wildfire Smoke and Indoor Air Quality

Wildfire smoke is a complex mixture of gases and fine particles produced when wood and other organic materials burn. The most concerning component is particulate matter (PM2.5), which consists of microscopic particles that can penetrate deep into the lungs and even enter the bloodstream. Exposure to PM2.5 can exacerbate respiratory conditions, trigger cardiovascular issues, and pose serious health risks to vulnerable populations, including children, the elderly, and those with pre-existing health conditions. WIRED+1Time+1 

How Wildfire Smoke Enters Indoor Spaces

Smoke can infiltrate buildings through various pathways: 

Air Leaks: Gaps around windows, doors, and other openings can allow smoke to seep indoors. Verywell Health+4WIRED+4Time+4 

Ventilation Systems: HVAC systems that draw in outdoor air can introduce smoke if not properly filtered or adjusted during wildfire events. 

Unbalanced Pressure: Exhaust fans without adequate makeup air can create negative pressure, pulling in smoky air from the outside. 

Understanding these entry points is the first step for implementing effective mitigation strategies. 

HVAC Best Practices for Mitigating Wildfire Smoke

To protect indoor air quality during wildfire events, consider the following HVAC best practices: 

1. Upgrade Air Filtration Systems 

Standard HVAC filters may not effectively capture the fine particles present in wildfire smoke. Upgrading to filters with a Minimum Efficiency Reporting Value (MERV) of 13 or higher can significantly improve filtration efficiency. These filters can trap smaller particles, including PM2.5, reducing indoor smoke levels. Canada.ca 

For enhanced protection, High-Efficiency Particulate Air (HEPA) filters can capture up to 99.97% of particles as small as 0.3 microns. However, it's essential to ensure that the HVAC system can accommodate these higher-efficiency filters without compromising airflow. HVAC Refresh 

2. Seal the Building Envelope 

Preventing smoke infiltration starts with a well-sealed building envelope. Use weather stripping, caulking, and other sealing methods to close gaps around windows, doors, and other potential leak points. This reduces the pathways through which smoke can enter the indoor environment. AireServ.com 

For more guidance on design and construction strategies that minimize wildfire smoke infiltration, see our article on Mitigating Wildfire Smoke in New and Old Residential Construction. 

3. Adjust Ventilation Settings 

During wildfire events, it's advisable to set HVAC systems to recirculate indoor air rather than drawing in outdoor air. This minimizes the introduction of smoky air from outside. Additionally, turning off exhaust fans that vent directly to the outside can help maintain indoor air quality. Oregon State University 

4. Incorporate Standalone Air Purifiers 

Portable air purifiers equipped with HEPA filters can provide additional filtration, especially in areas not served by central HVAC systems. These units are effective in reducing indoor concentrations of PM2.5 and other pollutants associated with wildfire smoke.  

5. Monitor Indoor Air Quality 

Utilizing indoor air quality monitors can help track pollutant levels, including PM2.5 concentrations. Real-time data allows for timely adjustments to HVAC settings and other mitigation measures to maintain a healthy indoor environment.  

An Inline HEPA Filtration Solution

For HVAC professionals seeking to enhance filtration capabilities, systems like the HS300 whole-house filtration system offers a practical solution. Designed to integrate with existing HVAC systems, the HS300 provides high-efficiency particulate filtration without significant modifications to ductwork. Its compact design and ease of installation make it suitable for both new constructions and retrofits, offering an effective means to improve indoor air quality during wildfire events. 

See How the HS300 Protects Indoor Air from Wildfire Smoke

Watch this simulation to see how the HS300 whole-house filtration system efficiently captures wildfire smoke particles, helping to maintain clean, healthy air indoors even during wildfire events.

Turning Wildfire Risk into Actionable Design

As wildfires continue to pose challenges across North America, proactive measures to protect indoor air quality are more important than ever. By upgrading filtration systems, sealing building envelopes, adjusting ventilation settings, incorporating standalone air purifiers, and monitoring indoor air quality, contractors can create healthier indoor environments. Implementing these HVAC best practices not only safeguards occupant health but also enhances the resilience of buildings against the pervasive threat of wildfire smoke. 

Sources:

  • U.S. Environmental Protection Agency. "Preparing for Fire Season." EPA.gov  

  • ASHRAE. "ASHRAE Releases New Guidance to Mitigate the Impact of Smoke on Indoor Air Quality." ashrae.org 

  • AVTECH. "Protecting Indoor Air Quality from Wildfires: Aligning with ASHRAE Guidelines." avtech.com 

  • IAQ.Works. "Do Air Filters Help With Wildfire Smoke?" iaq.works 

  • HVAC.com. "What's the Best Air Purifier for Wildfire Smoke?" hvac.com 

  • The Guardian. "Who should get an air purifier and can it help with wildfire smoke?" theguardian.com