## 4 Discussion
### The Essential Elements and IoT Architecture Framework to Implement an IAQ Monitoring Study
#### 4.1.2 Sensors Selection  
This study primarily focused on providing information to readers who are unfamiliar with IoT devices. As such, the list of criteria in Section 2 is intended to limit sensor selection to those devices that would be appropriate. In selecting devices that are either commercial or consumer grade, we demonstrated the capabilities of purchasable devices that require little to no modification and be ready for deployment at each worksite for IAQ monitoring purposes. It is then expected that other COTS devices may be added or interchanged to meet user requirements. This study attempted to circumnavigate issues of vendor lock-in through the purchase of sensors from differing manufacturers. As can be seen in Table 3, each sensor was sourced from a different manufacturer. The final criterion for this study was the availability of the device such that the device was available for the planned monitoring dates. The second list of sensor selection was intended to assist potential adopters to ascertain whether a particular device is appropriate. To begin with, users must have knowledge of which IAQ parameters are to be monitored and understand the intention behind these  
Figure 12: Device Status Dashboard sample: (a) Indoor Air Quality Sensor last reading and (b) current status of gateway devices. choices. This is because sensing devices can monitor multiple parameters and therefore different combinations of devices will provide different utility. There are further considerations beyond the IAQ parameters, which include the quality of data, and sensing accuracy and resolution that are determined by manufacturer, as well as the physical mechanisms of the sensing device. For example, consider the Monnit ALTA open/close sensors that are event-driven and operate via magnetic detection switch. These sensors have an operation range of \(\frac{3}{4}\) inch between the magnets. They also generate a binary response to the activity of doors opening and closing, of which should be accurately captured and there is little room for error. In comparison, the Cloud Garden Climate Sensors take measurements every minute. They have a temperature accuracy of \(\pm 0.3\)\({}^{\circ}\)C and tolerances that vary slightly over different temperature ranges. Each parameter has a different resolution, e.g., the particulate matter has a resolution of 1 \(\upmu\)g/m\({}^{3}\). For some system integrators such accuracy and resolution may or may not be deemed acceptable; however, for the purposes of our study, the accuracy and resolution were deemed sufficient. During the deployment or implementation phase, the sampling rate of the sensor devices is one of the few parameters that can be adjusted on-the-fly. Sampling rate impacts the resolution of the data, which is governed by the frequency at which data are collected. While the accuracy and resolution of each reading are important, the frequency of these readings is important as well. For example, in any sensor that is capable of high accuracy measurements but at a low sampling rate, the data would not be representative for time-based monitoring studies. COTS devices often have a factory-configuration to sample data every 5 to 10 min. The factory configuration is often adjustable but not always to a significant degree. For our study, the sampling rates of the selected sensors varied from 1 min in the Cloud Garden sensors to 10 min in the SenseCap Barometric Pressure Sensors. The sampling rates of each sensor can be seen in Table 3. It is therefore recommended that the system integrator should investigate whether the considered sensing device is capable of meeting the data collection needs. It must be noted that there are trade-offs in relation to sampling rate. While it may seem beneficial to increase the sampling rate as much as possible for more data, it raises issues of data storage, costs, and battery life. The users should then observe and evaluate the environmental characteristics.