A self contained biological indicator is disclosed having a housing and an ampule disposed within the housing, the ampule having a first dome, a second dome and a sidewall. A cap may be coupled to the housing. The cap may include a projection that may be coupled to the ampule by, e.g., a friction fit. An insert may be disposed within the housing. The insert may include a well within which at least a portion of the bottom dome of the ampule may be disposed. The insert may also include a ramp that is angled relative to the central longitudinal axis of the ampule. The second dome of the ampule may contact the ramp. The insert may also include an arm or finger that extends above the well and has a stress concentrator disposed thereon such that it is also disposed above the second dome of the ampule and adjacent to the sidewall of the ampule. In use, the SCBI generates therein a first reaction force between the second dome of the ampule and the ram having a component directed transverse to a central longitudinal axis of the ampule. The component of the first reaction force causes a second reaction force between the sidewall of the ampule and the stress concentrator. The second reaction force breaks the ampule.