<![CDATA[Environmental conditions in calibration laboratories need to be monitored to support consistent measurement activities. This study aimed to develop an Internet of Things (IoT)-based prototype for monitoring temperature, humidity, and noise. The system integrated an ESP32 microcontroller, a DHT22 temperature and humidity sensor, a KY-037 noise sensor, a 16×2 I2C LCD, a buzzer, and the Blynk platform. An experimental engineering method was employed through system design, prototype development, and performance testing. Sensor readings were compared with reference instruments at three measurement locations, with ten measurements conducted for each parameter at each location. The results showed an average relative error of 0.53% for temperature, with a mean difference of 0.14 °C; 1.86% for humidity, with a mean difference of 1.08 %RH; and 1.69% for noise estimation compared with a sound level meter. The buzzer operated according to the programmed threshold, activating when the estimated noise level exceeded 40 dB(A). IoT testing confirmed that the three monitored parameters could be displayed on the LCD and transmitted to Blynk for access via a laptop or smartphone. The prototype can therefore serve as a supporting device for environmental monitoring and early warning in calibration laboratories under the tested conditions.]]>
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