Cleaning is the elimination of pollutants in a surface area to make it clean, and Kwunphi is the first to introduce quality standards for solar cleaning to define the degree of cleanliness. Define the cleaning quality according to the classification table of iso 14644-9 "surface cleanliness by particle concentration".

SCP Grade	≥5μm	≥10μm	≥50μm	≥100μm	≥500μm
SCP Level 2	20	10
SCP Level 3	200	100
SCP Level 4	2000	1000	200	100
SCP Level 5	20000	10000	2000	1000	200
SCP Level 6	200000	100000	20000	10000	2000
SCP Level 7	2000000	1000000	200000	100000	20000
SCP Level 8		10000000	2000000	1000000	200000