Patent ID: 7141214

Claim:
A method for indicating that an article has undergone ethylene oxide sterilization processing comprising: providing a water-based chemical indicator ink consisting essentially of at least one pH indicator dye selected from the group consisting of Bromocresol green, Bromophenol blue, Methyl red, Ethyl orange, and combinations thereof, and a powdered and crystallized hexahydrate metal salt; wherein said at least one pH indicator dye undergoes an irreversible color change when exposed to ethylene oxide vapor in the presence of low-temperature steam; applying said water-based chemical indicator ink to an article; subjecting said article to a concentration of ethylene oxide vapor in the presence of low-temperature steam; and observing said water-based chemical indicator ink for a color change that is visually indicative of whether said concentration of ethylene oxide vapor has been applied for a time sufficient to sterilize said article.