A method for controlling humidity, the method comprising: providing a chamber configured to receive objects to be sterilized; injecting a first quantity of water into the chamber as water vapor; determining a pressure rise and a pressure drop in the chamber resulting from injecting a first quantity of water into the chamber, wherein the pressure rise is the maximum chamber pressure detected after injecting water vapor into chamber (P2) minus the chamber pressure prior to injecting water vapor into chamber (P1), and wherein the pressure drop is the maximum chamber pressure detected after injecting water vapor into chamber (P2) minus the average chamber pressure 2 minutes after injecting the water vapor (P3); calculating an absorption ratio (AR) as the ratio of the pressure drop to the pressure rise as AR =(P2-P3) / (P2-P1); sensing the humidity of the chamber after injecting a first quantity of water to determine a first humidity value ( RH chamber ); comparing the first humidity value to a pre-selected humidity value ( RH setpoint ) to determine a humidity error ( RH error ), wherein RH error = RH setpoint - RH chamber ; and injecting a second quantity of water into the chamber as water vapor, wherein the second quantity of water is calculated based on the absorption ratio (AR) and the humidity error ( RH error ), and injecting a biocidal gas into the chamber after the injection of the second quantity of water. providing a chamber configured to receive objects to be sterilized; injecting a first quantity of water into the chamber as water vapor; determining a pressure rise and a pressure drop in the chamber resulting from injecting a first quantity of water into the chamber, wherein the pressure rise is the maximum chamber pressure detected after injecting water vapor into chamber (P2) minus the chamber pressure prior to injecting water vapor into chamber (P1), and wherein the pressure drop is the maximum chamber pressure detected after injecting water vapor into chamber (P2) minus the average chamber pressure 2 minutes after injecting the water vapor (P3); wherein the pressure rise is the maximum chamber pressure detected after injecting water vapor into chamber (P2) minus the chamber pressure prior to injecting water vapor into chamber (P1), and wherein the pressure drop is the maximum chamber pressure detected after injecting water vapor into chamber (P2) minus the average chamber pressure 2 minutes after injecting the water vapor (P3); calculating an absorption ratio (AR) as the ratio of the pressure drop to the pressure rise as AR =(P2-P3) / (P2-P1); sensing the humidity of the chamber after injecting a first quantity of water to determine a first humidity value ( RH chamber ); comparing the first humidity value to a pre-selected humidity value ( RH setpoint ) to determine a humidity error ( RH error ), wherein RH error = RH setpoint - RH chamber ; and injecting a second quantity of water into the chamber as water vapor, wherein the second quantity of water is calculated based on the absorption ratio (AR) and the humidity error ( RH error ), and injecting a biocidal gas into the chamber after the injection of the second quantity of water. <EOS>