The increasing interest in low-cost Smart Environmental Monitoring Systems (SEMS) leads to a constant use of off the shelf sensors and components. However, with a lack of validation and calibration of the sensors, the accuracy of the measurements should be questioned. Especially when it comes to the monitoring of living environments such as homes, offices, and classrooms, as individuals remain there for extended periods of time, and prolonged exposure to hazardous environments can lead to health problems and discomfort. The objective of this research is to shine the light on a constantly overlooked parameter, the accuracy of the measurements taken by the SEMS. In particular, the presented research focuses on the measurement science point of view and compares the accuracy of the typical sensors for living environment monitoring. The final aim is, in on one end, to stimulate the research in the field to define the desired accuracy in the different applicative sectors, and on the other end, to increase the awareness of both producers and consumers about the metrological aspects of the sensors they produce/use and of the overall monitoring systems.