Michigan Compiled Laws, Chapter 339. Occupational Code § 339.5801

(a) “Air conditioning” means the process of treating air to meet the requirements of a conditioned space by controlling, either simultaneously or individually, the air's temperature, humidity, cleanness, and distribution.

(b) “Board” means the board of mechanical rules described in section 805.  1

(c) “Cooling” means air conditioning as defined in subdivision (a).

(d) “Ductwork” means the air distribution arrangement for supply, return, and exhaust in air conditioning systems and in nonair conditioning systems, the materials and methods of which are specified in the Michigan mechanical code, or an equivalent nationally recognized model mechanical code. Ductwork includes flues, vents, and chimneys.

(e) “Fire suppression system” means an integrated combination of a fire alarm system and fire suppression equipment that as a result of predetermined temperature, rate of temperature rise, products of combustion, flame, or human intervention will discharge a fire extinguishing substance over a fire area.

(f) “Heating”, used alone, means the use of any fuel or electricity to generate heat in an air conditioning system. When used with a qualifying term such as “hydronic”, the term heating assumes the limited meaning expressed by that qualification.

(g) “Heating, ventilating, and air conditioning” or “HVAC” means the application of equipment and systems to provide air conditioning for occupants of buildings and structures. HVAC does not include the installation of portable self-contained refrigeration equipment and window-type air conditioners of not more than 1- 1/2 horsepower.

(h) “Hydronic heating and cooling” means the application of equipment and systems which provide air conditioning by the controlled forced circulation of fluids or vapors in pipes.