Underground mining is associated with various hazards including, gas poisoning, gas explosion and suffocation. All these and other dangerous mining situations pose a risk to the miners life. IoT can be used to enhance mining safety, thereby preventing minor and major injuries, and fatalities in mining workplaces. This paper presents the design and performance analysis of an IoT network based smart safety jacket for real time monitoring of health and safety of miners. This smart jacket is equipped with a carbon monoxide gas sensor, temperature and humidity sensor and Electrocardiograph (ECG) sensor. These sensors collect data which are transmitted to the control room wirelessly, through NRF24L01+ wireless module that is connected to the smart safety jacket. When the level of monitored data is beyond the critical level, an actuator on the smart safety jacket triggers an alarm warning the workers of the incident. For real-time communication and access from anywhere, the receiver system transmits instantly the received data to the cloud through ESP 8266 Node MCU wireless module. In response to the warning, the workers can take timely decisive decision to avert danger.