Most Americans spend up to 90% of their time indoors so the indoor air quality (IAQ) of their homes, schools, and work environments is a critical component of their wellbeing. Unfortunately, indoor pollutants can accumulate to levels that can pose health and comfort issues, particularly when there is too little outdoor air entering a building.

These pollutants may include mold, bacteria, tobacco smoke, volatile organic compounds (VOCs) and other chemicals, radon, allergens, elevated levels of carbon dioxide and carbon monoxide, and other substances. A common approach to lowering the concentration of indoor pollutants is to increase the amount of outdoor air being brought into a building. Outdoor air enters and leaves buildings through infiltration, natural ventilation, and mechanical ventilation.

When infiltration takes place, outdoor air flows into the building through openings, joints, and cracks in walls, floors, ceilings, windows, and doors. Air may also move out of the building in this manner in a process known as exfiltration. When natural ventilation takes place, air moves through open windows and doors. Air movement associated with infiltration and natural ventilation is caused by air temperature differences between the indoors and outdoors, and due to wind.

Mechanical ventilation devices, from exhaust fans that remove air from a single room to air handling systems that use fans and duct work to continuously remove indoor air and distribute conditioned outdoor air to points throughout a structure are common in many buildings. The rate at which outdoor air replaces indoor air is described as the air exchange rate.

“Whenever there is too little infiltration, natural ventilation, or mechanical ventilation, the air exchange rate is low and pollutant levels can rise,” said Michael Berrevoets, President, VOETS, LLC. “All too frequently, our building science professionals discover elevated pollutant levels in buildings that were designed and constructed to minimize the air exchange rate. To identify and prevent these types of issues, our experts utilize advanced instrumentation and years of experience to accurately diagnose and resolve both ventilation and IAQ issues. The end result is healthy air for all building occupants.”