The invention discloses a laundry article used for both cleaning and conditioning fabrics comprising a water-insoluble nonwoven substrate and coated thereon into at least one zone each a detergent composition and a fabric conditioning composition. A mass-analyzing method using an ion trap type mass spectrometer equipped with a ring electrode and one pair of end cap electrodes temporarily traps ions in a three-dimensional quadropole field to mass-analyze a sample. According to one method, natural gas fuel is delivered from said first and second sources into said surge tank via first and second conduits, each conduit having pressure-control valves and sensors.