Abstract: A method of sterilizing mattresses, laundry sacks and similar articles in a sterilizing apparatus comprising a sterilization chamber with a surface to carry said articles, and a circulation system which, besides said sterilization chamber includes a fan, a pressure pipe from the fan to the sterilization chamber and a suction pipe from the sterilization chamber to the fan. The sterilization is carried out in a work cycle comprising a combination of a gas-filling phase, a sterilizing phase, at least one gas-emptying phase, at least one ventilation phase and a final phase, the sterilization gas being removed from the circulation system during the gas-emptying phase by means of a water suction means and thus being mixed with water, while at the same time filtered air is added to the circulation system.