The process of welding adds diffusible hydrogen to steel, causing embrittlement of the weld. The steel could even explode if concentrations get too high. Although scientists have been detecting hydrogen with volumetric displacement since 1950 and with gas chromatography more recently, Rodney D. Smith II and his colleagues have developed a detection method based on fiber optics. Smith conducted the research for his doctoral thesis but has since been hired by DCH Technology to continue his work. Unlike previous techniques, the fiber optic sensor can be attached directly to steel, and the material can be analyzed in less than an hour (compared with more than 24 hours for traditional methods, and even up to a week, in some cases). The researchers are still working out some problems -- such as the most effective sealing method -- but their latest design has achieved detection as low as 0.1 percent hydrogen in argon. They have shown that the device can detect hydrogen in steel several hours after welding, without any special storing methods. Smith has conducted practical tests with HSLA 100 steel, which is used in shipbuilding by the US Navy.