What do you call mechanical systems that were installed before the adoption of the building code?

The term for mechanical systems that were installed prior to the adoption of current building codes is commonly referred to as "Existing Mechanical Systems." This terminology is used in the context of building inspections and code compliance to distinguish systems that are currently in place from those that are newly installed and subject to the latest regulations.

"Existing Mechanical Systems" acknowledges that these systems may still be in operation, even if they do not conform to newer standards. This distinction is important during inspections and renovations because it informs the inspector and building owner about what can remain in use, what may need to be upgraded, and how to approach compliance with current safety and efficiency standards.

The other terms, while they may describe similar situations, do not hold the same formal relevance in building code discussions. "Legacy Mechanical Systems" might be used in a historical context, while "Pre-Code Systems" could imply a focus on the time frame rather than the operational status. "Outdated Mechanical Systems" conveys a negative connotation that suggests the systems are no longer acceptable, which is not always the case as many existing systems can comply with safety even if they aren't built to current codes. Thus, "Existing Mechanical Systems" is the most accurate and widely accepted descriptor for such installations.