Abstract: Volatile organic compounds are removed from contaminated soil by introducing one or both of a water soluble peroxygen compound, such as a persulfate, and a permanganate into the soil, either in situ or ex situ, in amounts and under conditions wherein both the soil oxidant demand is satisfied and volatile organic compounds in the soil are oxidized. In a preferred embodiment, when both are used, the peroxygen satisfies the soil oxidant demand and the permanganate oxidizes the volatile organic compounds. Sodium persulfate is the preferred persulfate and potassium permanganate is preferred permanganate. The persulfate and the permanganate may be added to the soil sequentially, or may be mixed together and added as an aqueous solution.

Abstract: A photo-acoustic leak detection system for detecting a gas leaking from a component 30, includes at least two laser beams 24,26, incident on the component 30 and disposed so as to completely illuminate an inspection region 159 around at least a portion 28 of the component 30, each beam having a corresponding wavelength .lambda..sub.1 which is absorbed by the gas, the gas emitting an acoustic signal 36 when the gas absorbs light from at least one of the beams, an acoustic sensor 40, which receives the acoustic signals 36 and provides a sensor signal indicative thereof on a line 42 to a bandpass filter 44 and a synchronous detector 18 which provide a filtered signal indicative of the acoustic signal 36 on a line 50 to a signal processor 52. The processor 52 provides an output signal indicative of the leak in the component 30.

Abstract: A photo-acoustic leak detection system for detecting a gas leaking from a component includes a beam, having a wavelength, incident on the component and producing an acoustic signal. A second acoustic signal is also produced when an air source dilutes the gas leaking from the component. A signal processor receives sensor signals indicative of both acoustic signals and uses the second sensor signal as a non-leak baseline measurement and provides an output signal indicative of whether a leak exists.

Abstract: A photo-acoustic leak detection system for detecting a gas leaking from a component (30), includes at least one laser beam (20), incident on the component (30) and having a wavelength which is absorbed by the gas, the gas emitting a photo-acoustic signal (36) when the gas absorbs light from the beam (20), the beam (20) being pulsed at a pulse frequency, the pulse frequency being related to a detection frequency of the photo-acoustic signal and being a frequency at which the magnitude of background acoustic noise at the detection frequency is at a predetermined low level, at least one acoustic sensor (40), which receives the photo-acoustic signal (36) and provides a sensor signal on the line (42) indicative thereof to a filter (44) and a synchronous detector (18), which provide a filtered signal on a line (50) to a signal processor (52). The processor (52) provides an output signal on a line (54) indicative of the leak in the component.