These biological indicators contain Bacillus stearothermophilus spores especially resistant to the steam sterilization process. Following the sterilization cycle, the vial is crushed to provide media that will promote the growth of any spores that may not have been killed during the sterilization process. An easily detected colour change in the vial indicates that the sterilization process was not successful. Final results are obtained in 48 hours. Daily monitoring of the steam sterilization process is recommended.