一尘不染 [yī chén bù rǎn]

• maintain one's original pure character; as clean [neat] as a (new) pin; be spotlessly clean; free from dust; maintain personal integrity (during chaotic times); not be contaminated by the world; not to be stained [soiled] with [by] a particle [speck] of dust; remain uncontaminated; spotless; There is not a speck of dust.:

  The apparatus is spotlessly clean.

  仪器上一尘不染。