Maintenance of sewage systems requires workers to enter confined manholes, where hazardous gases can build up. These toxic, flammable gases create a serious safety risk. To address this problem, a portable gas monitoring system based on IoT technology was designed for real time sensing and observation. The proposed system comprises of MQ- 4, MQ-6, and MQ-7 gas sensors, along with a DS18B20 temperature sensor, all interfaced to an ESP32 microcontroller. The data is then transmitted to a cloud platform built with Node.js and MongoDB, enabling real-time monitoring. Whenever the gas concentrations exceed the safety limits, alerts are triggered to enable early action. The experimental results show an accuracy of approximately ±2% compared to standard measurement instruments, with the latency less than 500 ms. Early warning of dangerous gas levels can significantly reduce risks during sewage maintenance.
Harikrishnan et al. (2026) studied this question.