Project Summary/Abstract NIOSH conducts activities to assure safe and healthful conditions for American workers. This proposed project addresses a NIOSH mission objective for innovative solutions that provide practical methods to identify and measure hazards at a reasonable cost in high-risk occupations (e.g. mining). The mining industry presents particularly challenging safety and health needs. Despite well-regulated safety procedures, accidental explosions and toxic gas inhalation continue to cause coal miner deaths. To help prevent such tragedies, technologies are needed that sense and measure, from a distance, concentrations of explosive or other life-threatening hazards including methane, carbon monoxide, hydrogen sulfide, ammonia, and dust. These technologies can warn miners of immediately dangerous conditions within or prior to entering potentially hazardous areas. Technologies such as the widely deployed backscatter Tunable Diode Laser Absorption Spectroscopy developed and commercialized by Physical Sciences Inc. (PSI) for natural gas leak surveying using handheld laser tools, enable sensing explosive or toxic environments from afar by safely illuminating the region of interest with a laser beam. Previous NIOSH/CDC/OMHSR research demonstrated the use of this technology to detect areas of high methane concentrations along mine wall faces. The technology is adaptable to measure each of the hazardous gases listed above. Recently, PSI developed the ability to utilize this technology to create quantified images of small methane plumes, and to utilize the quantitative information to deduce the plume flux (i.e. emission flow rate). The Phase I project demonstrated a lightweight and compact design of the transceiver head that will enable a handheld imaging tool for the visualization and quantification of potentially hazardous methane emission sources, as well as detection of stagnant methane pockets, in coal mines. The Phase II objectives are to: 1) develop a handheld prototype, and 2) evaluate the prototype in relevant environments. The Phase II specific aims are to: 1) develop a prototype handheld imaging sensor incorporating the optical and electronic components along with data analytics algorithms that can be used for field testing; 2) challenge the prototype in controlled and real environments; 3) analyze the data, improve the analytics, and revise prototype. Tasks to achieve these aims include: reducing footprints of electronics, mechanical and optical components; integrating all sub-systems into a compact package; designing and modifying toward intrinsically safe device; developing and modifying firmware and software; conducting open and confined laboratory tests; analyzing results, and; revising prototype and algorithms.