What term refers to mechanical systems that were installed prior to the adoption of code?

The term that accurately describes mechanical systems installed prior to the adoption of code is "Existing Mechanical Systems." This term is commonly used in the industry to refer to equipment or systems that are already in place and operational, regardless of whether they meet current code requirements. Existing mechanical systems may not conform to the latest code standards due to the changes and evolution of applicable codes over time.

In contrast, other options do not specifically convey the idea of prior installation relative to code adoption. "Legacy Mechanical Systems," while potentially referring to older systems, can imply a sense of nostalgia or historical significance, rather than merely indicating their installation status regarding code compliance. Similarly, "Outdated Mechanical Systems" suggests that the systems are no longer effective or relevant, which does not consider their operational status or compliance with previous codes. "Traditional Mechanical Systems" may evoke systems that follow established conventions, but does not necessarily indicate that they were installed before current codes were implemented.

Overall, "Existing Mechanical Systems" accurately captures the essence of systems that have been in place prior to the adoption of updated codes and their context within building safety and regulation standards.