The presence of deposits in pipes and equipment, or the appearance of leaks, is the driving force for considering a cleaning program. The choice between cleaning or pipe replacement, on-line or off-line cleaning, or the selection of the specific cleaning program used, all depend upon a detailed knowledge of the systems involved. The amount of advance preparation, the selection of the cleaning method, the specific chemical program, and the degree of performance monitoring are all shown to critically affect the success of the program.

• Considerations for on-line and off-line cleaning of HVAC piping systems | Semantic Scholar
• Considerations for on-line and off-line cleaning of HVAC piping systems (researchgate.net)
• Considerations for on-line and off-line cleaning of HVAC piping systems (Journal Article) | OSTI.GOV
• AMPP Store – 96523 CASE HISTORIES OF ON-LINE AND OFF-LINE CLEANING OF HVAC PIPING SYSTEMS (nacestore.azurewebsites.net)