3M Attest Biological Indicators for steam. The self-contained BI for 250 °F / 121 °C gravity 270 °F / 132 °C vacuum-assisted steam cycles consist of a {I}Geobacillus stearothermophilus{IP} spore strip; sealed glass ampule with growth medium and a bromocresol purple pH indicator system; brown color-coded cap with holes for sterilant penetration and a hydrophobic filter as a bacterial barrier, and a chemical indicator on the label that 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 a visual change readout. A color change to yellow indicates surviving spores and a positive result.