Air quality is an important environmental concern, as it is strictly related to human health risks and adverse effects on it. Monitoring air pollutants and different ancillary parameters is a feasible and crucial approach to address this challenge. This task typically involves high expenses in case measurements are carried out by using conventional measurement instruments and human operators. However, utilizing measurement systems with low-cost sensors can reduce the overall implementation effort. The aim of this paper is to describe the sensor node architecture applicable to a general monitoring system and based on this structure, review different current low-cost measurement system proposals for outdoor air quality monitoring.