Dear Sir,
WHO TRS 957 dictates that “For grade B (at rest) the airborne particle classification is ISO 5 for both particle sizes considered” that means at rest condition 3520 particles of 0.5 micron and 29 particle of the 5.0 micron however for the same grade at operational condition same guideline dictates the limit of 352000 particles of 0.5 micron and 2900 particle of the 5.0 micron where’s the ISO class 6 ( Resemble to grade B) defined the limit of the 35200 particles of 0.5 micron and 290 particle of the 5.0 micron.
Why WHO TRS 957 considered grade B (at rest) as the grade A or ISO class 5…??
Regards
Mradul Gupta