In a flammable vapor sensor-based shut-off system of a fuel-fired water heater the sensor resistance output signal degradation caused by aging of the sensor is automatically compensated for using an operational timer having an output signal indicative of the total life of the sensor subsequent to its installation on the water heater. The method includes receiving the seismic data acquired by at least two receivers that are disposed at different depths. An apparatus for making a tampon and a tampon made by the method are also disclosed. The method also includes receiving image data which represents a plurality of images and processing the signal and the data to obtain a shape collage of the images which at least partially covers and conforms to the area of the at least one desired shape.