One common approach to lowering the concentration of indoor air pollutants is to increase the amount of outdoor air coming in. Outdoor air enters and leaves a home by infiltration, natural ventilation and mechanical ventilation.

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

There are also a number of 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 filtered and conditioned outdoor air to strategic points throughout a building. The rate at which outdoor air replaces indoor air is described as the air exchange rate. When there is little infiltration, natural ventilation or mechanical ventilation, the air exchange rate is low and pollutant levels can rise. 

It is not uncommon to find elevated pollutant levels in buildings that were designed and constructed to minimize the amount of outdoor air moving into and out of the structure, especially in energy efficient buildings. At CSC, our building science professionals are regularly called upon to investigate indoor air quality issues, and most of the time, a building's ventilation system plays a critical role in these investigations.  By utilizing advanced instrumentation and decades of experience, our team can quickly diagnose and resolve both ventilation and IAQ issues.