(a) An air conditioning and refrigeration contractor license must be endorsed with one or both of the following endorsements:
(1) an environmental air conditioning endorsement; or
(2) a commercial refrigeration and process cooling or heating endorsement.
(b) An environmental air conditioning endorsement entitles the license holder to engage in air conditioning and refrigeration contracting for environmental air conditioning within the class of license held.
(c) A commercial refrigeration and process cooling or heating endorsement entitles the license holder to engage in air conditioning and refrigeration contracting for commercial refrigeration and process cooling or heating within the class of license held.
(d) A license holder may not engage in a type of air conditioning and refrigeration contracting for which the person's license is not endorsed.