A biological indicator for testing the efficacy of sterilization or disinfection processes of closed environments or confined spaces, the biological indicator comprising a carrier; biological material supported on or embedded in the carrier; and a carrier container comprising a body and a cap. The carrier is fixed within an inner space of the cap, the cap being able to be placed in an open position completely exposing the carrier and the biological material to the closed environment or confined space to be disinfected. A method for determine the efficacy of a process of sterilization or disinfection of closed environments or confined spaces, preferably by means of an enzyme and a fluorescence compound, using said biological indicator.