A sterilizer apparatus comprises a sterilizer chamber (601), wherein the sterilizer apparatus is configured to inject steam into the sterilizer chamber (601). A measurement probe (400) is provided comprising a measurement chamber (3) having a fluid connection to the sterilizer chamber (601). A light source (1) emits light into the measurement chamber (3) and a light detector (2) detects the light in the measurement chamber (3) and convert the detected light into a detection signal. The measurement chamber (3) comprises an orifice (14) for supply of a gas. The sterilizer apparatus can perform a sterilizing process to sterilize a load (605), and automatically blow the gas through the orifice into the measurement chamber before or after the sterilizing procedure.
