Patent ID: 7608217

Claim:
A process for humidifying an atmosphere in a sterilization chamber to a target relative humidity, the process comprising the steps of a) providing an amount of water in a water reservoir at a reservoir temperature T s at or above a temperature of the chamber atmosphere T c ; b) reducing a pressure in the chamber to a value below the boiling point of water at the reservoir temperature T s , c) bringing the reservoir into fluid communication with the chamber via a conduit for exposing the water in the reservoir at the temperature T s to the reduced pressure in the chamber for a preselected exposure time so that water in the reservoir is boiled and to allow resulting water vapour to enter the chamber and disconnecting said fluid communication after said preselected exposure time; and repeating at least steps b) and c) a plurality of times, wherein at least one of the amount, of water and the exposure time are controlled such that the relative humidity in the chamber progressively increases with each repetition until the target humidity is reached and wherein after each step c) the conduit is closed for a time sufficient to heat the water in the reservoir and to adjust the reservoir temperature T s so that the reservoir temperature T s is equal to or above the temperature T c of the chamber atmosphere, and a temperature differential ΔT during each step c) is controlled to maintain the temperature T c of the chamber atmosphere substantially constant, wherein ΔT is defined by the formula ΔT =T s −T c .