Abstract: A system for forming a blocking layer of water-saturated soil surrounding the foundation of a building to be protected from ingress of radon gas or other soil gas contaminents. The system includes at least one set of parallel positive and negative electrodes positioned in the soil, adjacent and spaced from the foundation. Typically, the negative electrode will be positioned closest to the foundation. A low level voltage is applied to the electrodes from a DC power source. One or more sets of such electrodes will be positioned in the soil surrounding the foundation or at least that portion of the foundation most susceptible to gas ingress.

Abstract: Apparatus and method are provided for reducing rapping reentrainment from a conventional electrostatic precipitator. Thus, the apparatus will include a conventional electrostatic precipitator having at least one main electrical section and, in sequence downstream of the main electrical section, a precharger and a reentrainment collector. The precharger has a tubular anode aligned with collection plates in the main electrical section and a corona discharge wire aligned with the corona discharge wires of the main electrical section. The reentrainment collector includes collection plates substantially shorter than the collection plates of the main electrical section with at least one corona discharge wire in each of the gaps between the collection plates. The secondary collection plates of the reentrainment collector are operated at a current density 75% or less of the current density at which the main collector plates are operated.