By Doug Downie, CAD Designer

Throughout the world, wildfires are becoming larger and more frequent. The effects of breathing wildfire smoke are of increasing concern to building owners and occupants. Even as I write this article from my office in Central Oregon, our skies are clouded with the smoke from nearby fires. Colleagues in adjacent states also feel the impact from fires in their backyard along with the smoke plumes that carry across state borders.

Understanding Wildfire Smoke

But what is wildfire smoke, and why is it harmful? Wildfire smoke is a complex mixture of carbon dioxide (CO2), water vapor, carbon monoxide (CO), hydrocarbons, other organic chemicals, nitrogen oxides (NOX), trace minerals, and particulate matter. While many of these components are known to have deleterious health effects, the particulate matter (PM) generated by wildfires can have  a significant impact to the human body.

Particulate matter consists of solid particles and liquid droplets suspended in the air. Particles with diameters less than 10 microns (PM10) irritate the upper respiratory tract and eyes. But the smaller particles (PM2.5)  cause the greatest health concern because they can be inhaled deep into the lungs and can affect respiratory and heart health.

Wildfire smoke can enter a building through the building openings in the form of natural ventilation and infiltration, and also through the HVAC mechanical ventilation systems.  While we can either manually or electronically close the outside air intake of HVAC equipment, levels of carbon dioxide breathed out from the occupants can rise inside the building, negatively affecting the indoor air quality as noted in the1989 EPA Report to Congress which concluded that improved indoor air quality can result in higher productivity and fewer lost workdays.