Dry heat sterilization was one of the earliest forms of sterilization practiced. This process is accomplished by utilizing conduction methods (heat is absorbed by the exterior surface and passed inward to the next layer). Dry heat does most of the damage by oxidizing molecules. The essential cell components are destroyed and the organism is killed. Exposure times for these cycles tend to be a longer duration, typically 1.5-3 hours. Section <1229.8> in USP covers this process. According to USP, “dry heat sterilization is a process utilized for heat-stable items (glass, stainless steel, nonaqueous liquids, powders, etc.) that are unsuited for steam sterilization because of either an absence of water (nonaqueous liquids and powders) or requirements for absolute dryness following processing (product contact parts for nonaqueous products).” This process is focused on sterilization, rather than depyrogenation.
This chapter provides guidance for:
- Sterilization cycle control
- Validation of dry heat sterilization
- Equipment qualification
- Empty chamber temperature distribution
- Component mapping
- Load mapping
- Biological indicators
- Heat penetration and microbiological challenge
- Routine process control
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