The present invention is concerned with a process for the preparation of 2n-butyl-4-spirocyclopentane-1-biphenyl-4-yl)methyl-2-imidazolin-5-one hydrochloride, irbesartan hydrochloride, novel hydrated and anhydrous crystalline forms thereof, amorphous irbesartan hydrochloride, formulations containing the same, therapeutic uses thereof and methods of treatment employing the same. In addition to this, a system mounted on a panel is intended to make higher and more versatile in the functionality. The print emulation command set is used when the printer unit is controlled, and the designated command set is used when the data processing unit is controlled. An ECU calculates a secondary airflow rate based upon difference pressure between both secondary air supply pressure which is detected by the pressure sensor when the openingclosing valve is opened under such a condition that the secondary air pump is operated, and also, shutoff pressure which is detected by the pressure sensor when the openingclosing valve is closed.