The building industry typically focuses on delivering higher quantities of outdoor air as a proxy for occupant wellbeing. The quality of that outdoor air claimed center attention across Washington State with unhealthy ratings for a significant part of August. Now that the smoke has settled, it’s important to examine how outdoor air quality impacts the air we breathe indoors and what can we do to improve our indoor air quality.
Michael Frank.
As mechanical engineers in the heating, ventilation and air-conditioning (HVAC) industry, we have gained substantial indoor air quality knowledge from working with clients and monitoring our own facilities. A few of the lessons learned are that more outdoor air does not guarantee better indoor air quality and that not all filters are created equal.
Pollutants are typically measured as particulate matter (PM), which quantify substances in micrometers or one millionth of a meter. The typical industry scale ranges from 0.3 to 10. To define the scale a little more as an example, PM2.5 includes all particulate matter 2.5 micrometers and smaller. Smoke is typically measured at PM2.5, but can be as large as PM10 when visible ash is present. In actuality, much of the mass of smoke in PM2.5 is often in the 0.5 to one micrometer size. This is where differences in air filters can make a big impact.
