A systematic review of low-cost sensors with the Internet of Things application

In residential buildings that are private, autonomous and occupied spaces for most of the time, keeping a adequate IAQ level is necessary, especially when there are children, elderly or other vulnerable users. Within the development of sensors, its low-cost feature with adequate accura-cy and reliability, and Internet of Things (IoT) application make them affordable, flexible and feasible even for ordinary occupants to do IAQ monitoring in their homes. This systematic re-view searched papers from Scopus and Web of Science about the low-cost sensors (LCS) and IoT applications in residential IAQ research and 23 studies are included with targeted research contents. This review summarizes the information of: (1) applied existing sensors and their tar-get pollutants; (2) methods of IoT applications in the residential building; (3) applied LCS cali-bration methods; (4) applied existing micro-controller units; (5) reference cost of sensors and devices. This review also discusses several topics related to: (1) the cost and affordability of IAQ monitoring devices; (2) LCS calibration methods and their features; (3) possible solutions for increasing the feasibility of IAQ monitoring in residential buildings; (4) limitations of long-term IAQ monitoring in residential buildings