Mechanical ventilation systems, designed to meet ANSI/ ASHRAE Standard 62-1989 and to modify building pressures, were installed in two New Mexico elementary schools to reduce elevated levels of indoor radon, carbon dioxide, and airborne particles. Although the systems did not meet design conditions for outdoor air delivery, ventilation rates were increased by factors of 2 to 4 over pre-existing natural ventilation rates, and levels of the studied indoor air pollutants were significantly reduced. Operation of the ventilation systems reduced radon levels from 10 pCi L-1(370 Bq m-3), or greater, to less than 1.9 pCi L-1 (70 Bq m-3). The additional ventilation reduced average mass (PM10) and average count (particles greater than 0.5 µm) concentrations of airborne particles approximately 10% to 70%. Continuously collected data indicated that occupants and their activities were the dominant source of indoor particles. There was good correlation between side-by-side measurements of particle mass and count concentrations. Average pre-existing indoor concentrations of carbon dioxide (CO2) were reduced from 20% to 60% by the additional ventilation but not always below ASHRAE’s guideline of 1000 ppm. Estimates of the additional energy cost to operate the ventilation systems ranged from $700 to $1300 per year.

Paper from IAQ 1997 -- Design, Construction, and Operation of Healthy Buildings: Solutions to Global and Regional Concerns