6A fill assembly sterilization system for a blow/fill/seal machine utilizes a closed loop circulation of sterilant containing gas. A typical sterilant is nitrogen dioxide. The closed loop includes a shroud that defines a plenum and encloses the fill system and at least one high efficiency particulate absorption (HEPA) filter. Sterility assurance level of 10 can be achieved by subjecting the fill system to the sterilizing gas for at least 20 minutes at a temperature in the range of about 18°C. to about 30°C.
