The portable tank should be inspected along with the instrument, but it requires additional attention. Because the tank is a pressure vessel, care should be taken to insure that it is not dented or dropped. If the valve should be inadvertently knocked off, the tank could become a rocket and cause great damage. US Department of Transportation (DOT) regulations require that the tank receive a hydrostatic test every five years. The last date tested is stamped on the top (shoulder) of the cylinder body. Most compressed gas supply stores can perform this pressure test. If it is not possible to have the tank tested locally, return it to PMS Instrument Company for testing and inspection.