Smoke Season and Protecting Your Indoor Air Quality

Smoke Season and Protecting Your Indoor Air Quality

If you live in the West, you are surely tired of the ongoing, and seemingly ever-expanding, wildfire season. This year, more than 2 million acres of land have burned in California alone and another 800,000 acres have burned in Oregon and Washington. With wildfires becoming more frequent and more intense, a new term has entered our vocabulary: ‘smoke season’.

According to the U.S. EPA, the main pollutant emitted from wildfire smoke is fine particles 2.5 microns in diameter or smaller (also known as PM2.5.) This pollutant poses a major public health concern because it’s small enough to enter the lungs and even the bloodstream where it can cause serious complications. Fortunately, one of the primary benefits of Passive House is the excellent indoor air quality provided by high levels of airtightness and the ability to filter all your air through a heat recovery ventilation (HRV) system. Filters can be highly effective at removing pollutants from wildfire smoke and also dust, pollen, mold, bacteria, and other airborne particles.

The LUNOS e² is a unique, decentralized HRV system that requires no duct work to deliver fresh air or remove stale air from the home. It is easy to install and uses very little energy (measured in W/CFM) as compared to other HRV systems. 475 has begun offering a higher level of filtration for the LUNOS e². This LUNOS MERV 13 Filter/Interior Cover can remove up to 89.9% of particle pollution sized 1-3 microns and 90% or more of particles sized 3-10 microns. It is compatible with any LUNOS e² system. (Note: the LUNOS MERV13 Interior Cover is not compatible with the LUNOS eGO system.)

LUNOS MERV 13 Interior Cover

To further improve indoor air quality during smoke season, we recommend using standalone HEPA air purifiers in tandem with the LUNOS e². All HEPA filters have a MERV rating of 17 or higher, and can remove at least 99.97% of air particles between 0.3-1.0 micron in size. Learn more about HEPA filtration here.


As the background level of pollutants continues to rise—smoke being a major offender—good filtration is key. But it’s also critical to mention that above a certain level of pollution, air can no longer be filtered. Take Tahoe City, which just logged a record-breaking Air Quality Index (AQI) reading of 620 from the nearby Caldor fire, literally “beyond Index” (the highest possible rating is 500.)

If you live close to, or downwind of an active fire, make sure to regularly monitor your area’s AQI and shut off the ports to your ventilation system if it reaches an unhealthy level. One great way to understand the air quality in your own home is to purchase an indoor air quality monitor - here's a few good suggestions. At a minimum the monitor you choose should monitor indoor CO2 —an indicator of how stale the air may be. CO2 levels in homes without a dedicated fresh air system can easily rise above 1,000 parts per million, causing a range of negative health effects for occupants. By contrast, clean indoor air can lower the risk of heart disease, improve cognitive function, and elevate overall mood and satisfaction — benefits we can probably all agree are well worth the investment.