A technique for reducing noise in a digital video signal is disclosed. 1 in the spectral range between 600 nm and 2 \u03bcm, and wherein the extinction coefficient k of the material for the particles is greater than 0. For incident illumination at a principal angle greater than 60 degrees from normal, light is reflected from the internal reflection surface and emitted from the exit surface at an emitted light angle that is within 5 degrees of the target angle. The sensors may be internal or external to the inflation tool. If the integrity loss affects the cluster network environment, then a new cluster network environment may be created from a healthy node or a restored healthy node. An inlet through which water is intermittently charged is provided in the bottom portion of the liquid retention container, and a pressure-proof valve is provided in the inlet so as to close the inlet.