Mining Contract: Wireless Sensor Network with Methane Gas Cloud Detector and Absolute Pressure Sensor

Contract Status & Impact

This contract is complete. To receive a copy of the final report, send a request to mining@cdc.gov.

Continuous real-time sensing of hazardous atmospheric gases and environmental conditions in underground mines, with feedback to the mine operation center, provides a proactive knowledge of potentially dangerous areas. The mine ventilation system controls airflow distribution and ventilation capacity to ensure air quality for safe and efficient mine operations by diluting contaminants and controlling the air temperature and humidity. Atmospheric gas conditions can change rapidly in an underground mine as the pressure variations occur within the ventilation system. Methane gas can appear at explosive levels where it is not typically suspected or during non-routine tasks. To significantly reduce the risk for a methane explosion, it is critical to capture methane, air pressure, and temperature and humidity readings within the mine in near real-time and provide feedback to the mine operation center.

Under this contract, Innovative Wireless Technologies, Inc., was responsible for developing a battery-powered, MSHA-approved wireless sensor to detect absolute pressure, temperature, and humidity as well as methane gas and carbon monoxide gas in a mine. This sensor was designed to serve three purposes: (1) conduct absolute pressure measurement and recording in both non-permissible and permissible areas of a coal mine; (2) explore methane gas cloud detection, measurement, and visualization; and (3) provide a wireless sensor node network. This sensor network was used in conjunction with the SENTINEL™ Communications and Tracking system developed under a previous contract, which enabled the operator to conduct continuous monitoring and make adjustments to ventilation systems accordingly.

The prototype wireless sensor system was tested in a laboratory and in a working mine. The testing revealed that this pressure sensor was not sufficiently accurate in producing useful airflow estimations. It was determined that the LPS25H sensors currently available cannot effectively support the vision of enhancing mine safety by monitoring ventilation airflows in underground coal mines. The intake air in a mine varies with the time of day, local weather conditions, and the temperature of the air that fluctuates as it moves through the mine. Therefore, enhanced pressure sensors that are less susceptible to variations in temperature and humidity need to be used. A multiple wireless methane sensor system was chosen to monitor and detect methane clouds.

As a result of this research, a wireless sensor system was developed that demonstrated the following: 

• The ability to remotely measure and monitor absolute air pressure and temperature in an underground coal mine using intrinsically safe, battery-powered wireless sensors.
• The ability to detect and remotely monitor and follow the movement of a methane cloud in an underground coal mine adequately instrumented with intrinsically safe, battery-powered wireless methane sensors.
• The ability to measure and remotely monitor carbon monoxide levels in an underground coal mine using intrinsically safe, battery-powered wireless gas sensors.
• The ability to use a mine’s existing SENTINEL communications and tracking system for wireless subnetwork data of battery-powered wireless sensors.