However, state and federal governments often adopt these standards as regulations. Compliance with these standards is usually voluntary.
These standards reflect a consensus of expert opinions and extensive consultation with agencies of the U.S. Guidelines and standards published by the American Institute of Architects (AIA), American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE), and the Association for the Advancement in Medical Instrumentation (AAMI) form the basis of certain recommendations. The HICPAC system for categorizing recommendations has been modified to include a category for engineering standards and actions required by state or federal regulations. However, certain recommendations are derived from empiric infection-control or engineering principles, theoretic rationale, or from experience gained from events that cannot be readily studied (e.g., floods). The recommendations are evidence-based wherever possible. As in previous CDC guidelines, each recommendation is categorized on the basis of existing scientific data, theoretic rationale, applicability, and possible economic benefit.