A room is not a well-mixed reactor and concentrations will vary depending on the location of pollution sources and ventilation. But the concentration in the breathing zone is the most important concentration to be determined accurately, since this is directly linked to pollution exposure. These results indicate that future IAQ monitoring systems must carefully consider the location of sensors to ensure timely and accurate pollutant detection. Placing sensors, far from the walls, closer to breathing zones and pollutant sources yields data that more accurately reflects human exposure risks.