The recommended exposure time for dry heat sterilization at 160°C is 2 hours because dry heat requires longer exposure to ensure the complete destruction of microbial spores. Unlike moist heat sterilization, dry heat kills organisms by oxidation rather than denaturation, which is a slower process. Insufficient time at this temperature may lead to incomplete sterilization, risking contamination. Therefore, maintaining 160°C for 2 hours ensures effective sterilization of heat-resistant instruments without damage.

Reference: Principles and Practice of Infectious Diseases, Mandell, Douglas, and Bennett, 9th Edition.