Plasma cycling sterilizing process

Abstract

A method for plasma sterilization within a controlled temperature range includes exposing an article in a sterilizing chamber to a gas plasma flowing from a plasma generating chamber until the temperature in the sterilizing chamber rises to a preselected maximum temperature. The flow of the plasma gas to the sterilizing chamber is terminated until the temperature in the sterilizing chamber falls to a temperature below the preselected maximum temperature. These steps are repeated until sterilization of the article is effected. The temperature below the preselected maximum temperature when gas plasma flow is again initiated is preferably not more than 3.degree. C. below the preselected maximum temperature. The gas plasma can be generated from a mixture of gases consisting essentially of argon, helium, nitrogen or mixtures thereof; from 1 to 21 (v/v) % oxygen; and from 1 to 20 (v/v) % hydrogen; or a mixture containing from 1 to 10 (v/v) % oxygen and from 3 to 7 (v/v) % hydrogen; or a mixture containing 1 to 10 (v/v) % hydrogen and from 90 to 99 (v/v) % of argon, helium, nitrogen or mixtures thereof. Preferably the pressure in the sterilizing chamber rises to from 0.1 to 10 torr when the gas plasma is flowing into the chamber, and the pressure in the sterilizing chamber falls to a lower pressure when the gas plasma flow into the sterilizing chamber is terminated.