Mining Contract: A Compact, Wearable, Personal Monitor for Real-Time Detection of Nitrogen Dioxide in Mines

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Contract # 211-2013-56917
Start Date 8/20/2013
End Date 12/31/2016
Research Concept

This research was initially aimed at using liquid crystal technology to develop an affordable, compact, person-wearable methane monitor that would indicate unsafe methane levels. The technology was not deemed suitable for methane; however, it demonstrated promise for use in a person-wearable nitrogen dioxide sensor—the contract was redirected accordingly.

Topic Area

Contract Status & Impact

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

Mine workers would greatly benefit from a person-wearable monitor that will alert them to the presence of potentially hazardous levels of gases in their immediate work environment and empower them to make decisions as to the safety of their work area. Current monitoring devices are unreliable when exposed to changes in pressure, temperature, and interfering chemicals, or are too expensive for distribution among individual miners.

Under the original contract, Platypus Technologies, LLC, investigated the use of thin-film, liquid crystal technology for methane detection. When the liquid film crystal technology was exposed to low levels of methane, it was anticipated that the liquid crystal ordering would be disrupted and that the now randomly oriented molecules would no longer generate a net polarization of light and would appear dark between crossed polarizers. Thirty-seven different liquid crystals were tested; however, none satisfactorily responded to methane. Several alternative approaches to achieve acceptable liquid crystal response to methane were also attempted, with no success achieved.

Despite the failure of this technology to be a viable solution for methane, preliminary testing of liquid crystals’ response to nitrogen dioxide indicated a good probability of success. Nitrogen dioxide is emitted from a naturally aspirated diesel engine. Diesel engines are heavily relied upon by the industry and, after the use of treatment technologies to reduce particulate emissions, can cause an increase in nitrogen dioxide levels. Nitrogen dioxide overexposure causes several significant health effects—irritation to the eyes, nose, and throat; cough; chronic bronchitis; breathing difficulty; chest pain; pulmonary edema; and rapid heartbeat—but, as with methane monitors, the cost of nitrogen dioxide monitors is a significant barrier to distribution among individual workers. Therefore, this contract was modified and research is currently focused on the development of a compact, person-wearable, low-cost nitrogen dioxide monitor. Preliminary testing with the nitrogen dioxide monitor indicates a good probability of success.

Page last reviewed: July 18, 2016
Page last updated: July 18, 2016