A chemical sample gas tube that is capable of being rapidly heated and cooled allows rapid purging of condensed chemical vapor from its inside surface. The tube may include a thin foil with an electrically conducting surface, a rigidly separated pair of clamps to shape the thin foil into a cylinder shape, and a temperature-controlled source of electricity that can flow sequentially through the clamps and thin foil for heating. The temperature of the cylindrical thin foil may be increased at a rate of at least 25 degrees Celsius per second, and may be cooled at a rate of at least 10 degrees Celsius per second. A temperature control sequence may be provided that includes at least one temperature that performs at least one of: condensing the chemical vapor, transmitting the chemical vapor, desorbing the condensed chemical vapor, and decomposing the condensed chemical vapor.