Certol SM4340 ProChek ID Process Indicator Strip, Steam and Chemical Vapor, Pack of 1500. Certol SM4340 ProChek ID Process Indicator Strip, Steam and Chemical Vapor, Pack of 1500. Provides visible assurance that package or load was exposed to the sterilization process. Economical internal indicator for every load, every package. Strips may also be used in open, unwrapped loads. Indicator ink is temperature sensitive and turns from white to black in steam process and from white to brown in chemical vapor process. Indicator stripes on tape turn from white to black. Dual use to seal sterilization packaging and provide an external indicator. . Economical internal indicator for every load, every package. Strips may also be used in open, unwrapped loads. Indicator ink is temperature sensitive and turns from white to black in steam process and from white to brown in chemical vapor process. Indicator stripes on tape turn from white to black. Dual use to seal sterilization packaging and provide an external indicator. .