SECTION 1. Section 45A of Chapter 146 of the General Laws, as appearing in the 2002 Official Edition, is hereby amended by striking the first paragraph and inserting in place thereof the following new paragraph:-

No person shall operate or cause to be operated a refrigeration or air conditioning system, or any appurtenance thereof, excepting refrigeration or air conditioning systems in railway trains, motor vehicles, private residences, apartment houses of less than five apartments, refrigeration and air conditioning systems located on property under the jurisdiction of the United States government, refrigeration and air conditioning systems used exclusively for agricultural, horticultural or floricultural purposes, refrigeration and air conditioning systems having less than twenty tons capacity, and refrigeration and air conditioning systems that provide cooling for human comfort or process environment air conditioning and that meet all of the following criteria:  (a) has a capacity of less than 100 horsepower, (b) is a totally enclosed, factory-assembled complete unit, (c) is pad- or skid-mounted, (d) is located in an area that is separate from the space it cools, or on the roof of a commercial or industrial property, (e) has a unit enclosure containing the motor, compressor, condenser, receiver and associated piping, controls and safety devices, and (f) has an evaporator that is contained within the unit or is in the air.