Establishes the "Missouri Statewide Mechanical Contractors Licensing Act"

HB 547 creates a statewide licensing system for mechanical contractors in Missouri, replacing local licenses for most mechanical work. It directly affects contractors performing HVAC, boiler, piping, and other mechanical systems (like fuel gas or refrigeration) across the state, requiring them to obtain a state-issued license instead of local permits. Key provisions define "mechanical work" broadly to include installation and maintenance of systems such as HVAC, boilers over 120 gallons, and fuel piping, while excluding residential wood stoves, fire sprinklers, and work covered by national plumbing codes. The law establishes clear license categories (contractor, journeyman, apprentice) and specifies that residential work in single-family homes or small multi-unit dwellings may have separate rules.