Biological indicators monitor the effectiveness of the steam sterilization process and provide results within 24 hours.

Self-contained Biological Indicators (BI) for 121 °C (250 °F) gravity, 132 °C (270 °F) vacuum-assisted steam cycles. Consists of a Bacillus stearothermophilus spore strip, sealed glass ampule with growth medium, a bromocresol purple pH indicator system, color-coded cap with holes for sterilant penetration, and a hydrophobic filter as a bacterial barrier. A chemical indicator on the label changes from rose to brown when processed. After sterilization, the vial is 'crushed' to join the growth media with the processed spore strip. The BI is incubated for 48 hours for visual change readout. A color change to yellow indicates surviving spores and a positive result.