Spatial Resolution and Sensor Accuracy in Routine Indoor Air Quality Monitoring Networks: Are More Sensors Better? ✓ Most Recent

In commercial buildings with automation systems, adding more indoor air sensing in more locations could enable more effectiveventilation control through dynamic and spatial fine-tuning, helping to save energy, improve air quality, or both. But hownecessary and how useful is adding more than one air quality sensor per mechanical zone in typical commercial buildings withair-mixing mechanical systems, given the accuracy of available sensors? We assessed two approaches for locating from one up to10 sensors for measuring carbon dioxide (CO2) and the sum of volatile organic compounds (ΣVOC) in typical offices. Oneapproach was intended to determine the best possible performance, using optimal clustering of locations by their concentrationprofiles; the second simply sited each additional sensor in the mechanical system’s return duct and averaged readings. Eachapproach was assessed at three levels of sensor accuracy in four different office cases with high or low air supply rates and open orprivate layouts, and within a Monte Carlo analysis that varied hundreds of other relevant parameters. Results indicated thatconcentrations in areas served by a common mechanical system, given similar per-area supply flows and at least some airrecirculation, were reasonably homogeneous. The standard deviation of concentrations among locations was almost always lessthan 20% of the mean concentration, and was generally overwhelmed by sensor error when typical building grade sensors weremodeled. One implication was that capturing spatial distribution is likely to be less important than improving sensor accuracy,and without better quality sensors attempting to do so can actually increase network inaccuracy. If using and maintaining bettersensors is not possible, placing more typical building grade sensors in the return duct to provide redundancy can help reduceoverall error.