| dc.description.abstract | Chemical spills and gas leaks in chemical experiments can cause acid vaporization and other toxic and hazardous chemicals to appear in the laboratory. This research designs a fume hood with automatic exhaust fan speed regulation, detection of changes in acid concentration in the air, and an IoT-based real-time monitoring system. The system uses MQ-137, MQ-135, and MQ-8 gas sensors to detect changes in acid concentration as it evaporates in the air. The exhaust fan speed is automatically adjusted using a dimmer driven by a servo motor, controlled by the ESP-32 microcontroller based on the signal from the gas sensor. The test results show the output voltage of the MQ-137 sensor increases from 0.12V at 50 PPM to 0.35V at 250 PPM for nitric acid, and from 0.12V to 0.90V for sulfuric acid. The MQ-135 sensor increased from 0.15V to 1.03V for nitric acid and from 0.59V to 1.39V for sulfuric acid. The MQ-8 sensor increased from 0.04V to 0.22V for nitric acid and from 0.04V to 0.81V for sulfuric acid. The pH value decreased from 6.1 at 50 PPM to 4.9 at 250 PPM for nitric acid, and from 5.5 to 4.1 for sulfuric acid, indicating an increase in acidity. The servo motor remained at an angle of 60° unless the voltage was greater than 1V, at which point the angle increased to 180° to move the knob on the dimmer. The exhaust fan showed an increase in speed only at voltages greater than 1V. The solid state relay remained active throughout the test, and the buzzer activated at voltages greater than 2V as a warning sign. These results show the system is able to detect changes in acid concentration well and provide an important safety mechanism to avoid potential hazards. | en_US |
