are not particularly limited and include commercially available solvents in which contaminants are soluble or miscible such as terpenes esters polyalkylene glycols polyol esters polyvinyl ethers etc the flushing agent may include one or more cleaning agents suitable driving fluids or propellants for forcing the flushing agent out of the reservoir and into the vapor compression system include inert gases a preferred driving fluid is compressed nitrogen most preferably dry nitrogen turning to the drawings where like numerals indicate like elements fig1 shows a flushing agent reservoir 10 which in the embodiment shown is an aluminum cylinder the reservoir 10 can be refillable such as via an inlet in the reservoir 10 or can be a single use reservoir that is disposed of when emptied the reservoir 10 includes an opening 12 providing access to the interior of the reservoir in the embodiment illustrated the opening 12 has internal threads not shown which can mate in sealing relationship with corresponding external threads 13 on connecting member 16 of the cap 20 of flush unit 15 an o ring 14 can be carried in the annular groove 18 of connecting member 16 to ensure an effective seal between the cap 20 of the flush unit 15 and the reservoir 10 those skilled in the art will appreciate that other means of sealingly attaching the flush unit 15 to the reservoir 10 can be used and that the threaded connection illustrated is merely exemplary turning now to fig4 there is shown an embodiment of the cap 20 in the embodiment shown cap 20 includes.