There is provided a magnetic field generator in which separation and dislocation of permanent magnets from their permanent magnet groups is prevented easily and reliably for a long period of time without sacrificing productivity. The concentration of silicon in the phosphoric acid is controlled to maintain a desired level associated with a desired silicon nitridesilicon oxide etch selectivity. For example in a systems and methods according to the invention, clock speed may be reduced when the FIFO is relatively empty and increased when the FIFO is relatively full. Another port from the inner housing discharges water outside the outer housing and defines a static liquid level. The antifouling detergent for hard surfaces comprises a polymer comprising a monomer unit A having at least one group selected from amino groups and quaternary ammonium groups and a monomer unit B represented by \u2014SO2\u2014, in a specific ratio in the molecule.