The twenty-first century is known as the "Age of Science and Technology". By believing in the potential of technology to improve lives, people gain new experiences and come up with innovative innovations in response to how the global environment is changing as technology advances. With each passing day, the environment in our living space undergoes continuous changes. To address the crisis, a budget-friendly and beneficial environment monitoring system for the classroom was devised. This is an Internet of Things (IoT)-based initiative. To create a classroom monitoring system dubbed "IoT-Based Smart Environment Monitoring System," where Multi-purpose sensors, NodeMCU, a display, an alarm, Firebase, and IoT technology were employed. An Android-based user interface was developed for monitoring real-time temperature, humidity, gas, smoke, and other parameters. Thus, LPG gas, smoke, NH4, temperature, and humidity are detected and/or measured simultaneously with a user-friendly interface and a cheap cost.