Indoor Air Quality During Wildfires: Lessons and Solutions

Wildfires are a growing environmental and public health challenge, with their frequency and intensity increasing due to climate change. Recent wildfires in California serve as a stark reminder of the far-reaching consequences these events have on air quality—not just outdoors but within our built environments. While it’s essential to address the environmental causes and broader health impacts of wildfires, understanding their implications for indoor air quality (IAQ) is critical for safeguarding public health.

The Impact of Wildfire Smoke on Indoor Air Quality

Smoke from combustion of natural biomass is a complex mixture of particulate matter, carbon dioxide, water vapor, carbon monoxide, hydrocarbons and other organic chemicals, nitrogen oxides, and trace minerals. Fine particulate matter (or PM2.5), in particular, poses a significant risk as these microscopic particles can infiltrate indoor spaces, even in well-sealed buildings.

Wildfire-polluted air has high rates of oxidative and proinflammatory components, leading to irritation of the eyes, skin, and lungs, as well as acute respiratory and cardiovascular diseases. Long-term exposure can result in premature deaths, respiratory, cardiovascular and neurological effects like higher rates of dementia and depression. The main components of wildfire smoke that contribute to these harmful effects include:

Carbon Monoxide (CO): An odorless, colorless gas that replaces oxygen in the blood when inhaled, leading to symptoms like headaches, loss of muscle control, and in extreme cases, death.
Volatile Organic Compounds (VOCs): Chemicals that can cause nausea, blurred vision, and long-term organ damage. Common VOCs in wildfire smoke include formaldehyde, toluene, and polycyclic aromatic hydrocarbons (PAHs).
Nitrous Oxide (N2O): A gas that can impair memory and cognition and contributes to ozone layer depletion.
PM2.5: Fine particulate matter that can dissipate widely, may remain in the air formonths, and causes respiratory and cardiovascular damage.

Additionally, wildfires burning in the Wildland Urban Interface (WUI), where natural vegetation and human development intermingle, produce a different pollutant profile. WUI fires often involve the combustion of urban materials such as plastics, metals, and other synthetic substances. These materials release a more hazardous mix of pollutants, including halogens, dioxins, and heavy metals. Compared to traditional wildland fires, WUI fires result in elevated levels of formaldehyde, chlorine-based compounds, and other harmful emissions.

Given the hazards posed by wildfire smoke, managing indoor air quality is essential.

Mitigating Wildfire Smoke Indoors

1. HVAC Systems and Filters

Heating, ventilation, and air conditioning (HVAC) systems play a pivotal role in maintaining IAQ during wildfires. High-efficiency particulate air (HEPA) filters and those that are validated to be effective at capturing PM2.5 particles are recommended. Building managers and homeowners should:

Upgrade filters: Ensure HVAC systems use high efficiency, third party validated filters or higher to maximize particle removal.
Seal leaks: Inspect ductwork and windows for leaks that could allow outdoor air infiltration.
Operate systems continuously: Running the HVAC system in recirculation mode helps filter indoor air without bringing in polluted outdoor air.

2. Portable Air Purifiers

Portable air purifiers equipped with high quality HEPA filters are a practical solution for enhancing air quality in specific rooms. These devices can effectively reduce PM2.5 concentrations when selected and used correctly:

Check CADR ratings: The Clean Air Delivery Rate (CADR) should match the room size for optimal performance.
Place purifiers strategically: Position them in the most frequently used areas, such as bedrooms or living rooms, or create a single ‘clean room’.
Maintain filters: Replace filters according to manufacturer recommendations to ensure continued efficacy.

3. Respirator Masks vs. N95 Masks

Masks are essential when outdoor air quality is poor, but not all masks offer equal protection against wildfire smoke. Understanding the distinctions can help individuals make informed choices:

Cloth masks: While effective for reducing the spread of respiratory droplets, cloth masks provide minimal protection against fine particulate matter.
N95 masks: Certified by the National Institute for Occupational Safety and Health (NIOSH), N95 masks filter at least 95% of airborne particles, including PM2.5.
P100 Respirators: Capable of filtering toxic organic vapors so offer superior protection, especially important for those working outside during a wildfire or involved in the clearing process after the event.

For any mask, it is important to ensure a proper fit, using 2 straps to create an intact seal, and chin coverage in order to maximize its protective capabilities.

4. Indoor Air Quality Monitors

Real-time monitoring of IAQ empowers individuals to respond proactively to indoor pollution levels. Modern IAQ monitors can measure PM2.5, VOCs, and other pollutants, providing actionable insights:

Set thresholds: Identify safe levels for each pollutant and receive alerts when concentrations exceed them.
Correlate with outdoor conditions: Use monitors in conjunction with outdoor air quality indices to assess when to implement mitigation measures.
Promote awareness: IAQ monitors can educate occupants about the effectiveness of interventions like air purifiers and improved ventilation.

5. Rethinking Ventilation During Wildfires

High ventilation rates can sometimes worsen indoor air quality by bringing polluted outdoor air inside. During wildfires, strategies like recirculation are more effective. Use IAQ monitors to determine when ventilation is beneficial and avoid introducing more pollutants into indoor spaces.

6. Building Automation Systems

Using building automation systems (BAS) alongside outdoor air quality monitoring can help manage IAQ during wildfires. BAS can automate HVAC adjustments based on real-time PM2.5 levels, ensuring optimal indoor air quality with minimal manual intervention.

7. Managing Settled Dust Post-Wildfire

Even after the immediate wildfire threat has subsided, settled dust containing PM2.5, VOCs, and ash can linger indoors, posing ongoing health risks. Steps to mitigate this include:

Deep cleaning: Use vacuum cleaners equipped with HEPA filters to remove particulate matter from carpets and upholstery.
Surface cleaning: Wipe down hard surfaces with damp cloths to prevent dust resuspension.
Air circulation: Continue using portable air purifiers and HVAC systems with high-efficiency filters to remove residual pollutants from the air.

The Role of Policy and Governance

To effectively combat the health and economic risks posed by wildfires, comprehensive policy initiatives and governance strategies are essential. Policymakers must focus on:

Strengthening Building Codes: Mandating the use of validated high-efficiency air filtration systems in residential and commercial buildings, especially in wildfire-prone areas.
Funding Research and Innovation: Allocating resources to develop advanced IAQ technologies and better understand the long-term health impacts of wildfire smoke.
Public Education Campaigns: Governments and organizations should prioritize raising awareness about IAQ management during wildfires, including the use of masks, air purifiers, and HVAC system upgrades.
Collaboration Across Sectors: The private sector, researchers, and governmental bodies must work together to create standards and certifications for IAQ technologies and products, ensuring their efficacy and accessibility.
Emergency Response Frameworks: Implementing robust response plans for communities that include air quality monitoring, distribution of masks, and temporary relocation options for vulnerable populations.

At the iAIR Institute, we recognize the critical role of policy in promoting healthier indoor environments. Our mission includes advocating for evidence-based regulations, supporting innovation, and creating collaborative platforms that unite businesses, trade organizations, and governments.

Closing Thoughts

The recent devastating wildfires in California have highlighted the urgent need to address indoor air quality as part of wildfire preparedness and the need to improve preparedness in the face of future wildfire challenges. It will be by working together that we will mitigate the health impacts of wildfires and improve resilience within our built environment. At the iAIR Institute, we remain committed to empowering stakeholders with the tools, knowledge, and collaborative platforms necessary to transform indoor environments into spaces that promote health and resilience.