Toxic and Non-Toxic Gas Detection System for Septic Tank

Abstract

In septic tanks, various types of toxic and non-toxic gases are found such as Carbon-di-Oxide (CO2), Carbon-mono-Oxide (CO), Hydrogen Sulfide (H2S), Methane (CH4), and so on. In this paper, a toxic gas detection system for a septic tank has been presented, where MQ-135, MQ-136, MQ-4, and MQ-7 sensors are employed for combined detection of CO2, H2S, CH4, and CO gases respectively. With the change of concentration of gases, the sensor resistance changes, and accordingly an analog voltage is produced across the sensor. The analog voltages from the sensors are fed to a microcontroller, which reads the values and converts the values into gas concentration in PPM (parts per million). The PPM values for all four gases are displayed on an LCD, where two levels are assigned as “Safe” and “Danger” based on the concentration of each gas. “Safe” status means the concentration of gas is not harmful and “Danger” status means the concentration of gas is harmful. A buzzer will give an alarm when the gas concentration status becomes “Danger”. Furthermore, a Bluetooth device is interfaced with the microcontroller for transferring the gas concentration data to a smartphone. For the Smartphone, application software has been developed to monitor the concentration of each toxic gas. The prototype system has been developed and tested which gives satisfactory results. It is supposed to be a helpful and cost-effective system for cleaners working in septic tanks.