This publication provides guidance to owners of existing commercial buildings and their architects and engineers on security and operational enhancements to address vulnerabilities to explosive blasts and chemical, biological, and radiological hazards. It also addresses how to integrate these enhancements into the ongoing building maintenance and capital improvement programs. These enhancements are intended to mitigate or eliminate long-term risk to people and property. FEMA 459 can be used in conjunction with FEMA 452, Risk Assessment: A How-To Guide to Mitigate Potential Terrorist Attacks Against Building. FEMA 459 presents an integrated, incremental rehabilitation approach to implementing the outcomes of a risk assessment completed in accordance with FEMA 452.