An indirect method of measuring small concentrations of hydrogen gas in air in nearly real time has been devised to circumvent the difficulty of performing such measurements directly. In this method, a sample of air suspected of containing hydrogen is first enclosed in a suitable container, and its humidity is measured. The enclosed sample is then exposed to ultraviolet light (typically at a wavelength of 254 nm), which photolyzes the hydrogen to water vapor. The exposure time needed for photolysis is of the order of minutes, the exact value depending on the shape and size of the sample container.
After photolysis, the humidity of the sample is measured again. The concentration of hydrogen in the sampled air is deduced from the increase in humidity between the first and second readings. In the system used to demonstrate the feasibility of the method, the sample container was a Tedlar chamber and the humidity was measured by a hygrometer. In another proposed system, ultraviolet-exposed and non-ultraviolet-exposed air samples would be pumped through the reference and sample cells of an infrared- based analytical instrument that would be modified for measuring concentrations of water vapor.
This work was done by Jean Andino of the University of Florida for Johnson Space Center.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:
University of Florida
Environmental Engineering Sciences
AP Black Hall
P.O. Box 116450
Gainesville, FL 32611-6450
Phone No.: (352) 392-7814
Refer to MSC-23845-1, volume and number of this NASA Tech Briefs issue, and the page number.