AQL Inspection Manual
Normal inspection will be used at the start of inspection unless otherwise directed by the responsible authority. Once Normal, Tightened or Reduced inspection has been executed, it shall continue unchanged for each class of defects or defectives on successive lots or batches except where the switching procedures given below require a change. The switching procedures shall be applied to each class of defects or defectives independently.
Normal to Tightened
When normal inspection is in effect, tightened inspection shall be instituted when 2 out of 5 (or fewer) consecutive lots or batches have been non-acceptable on original inspection (i.e., ignoring resubmitted lots or batches for this procedure).
Tightened to Normal
When tightened inspection is in effect, normal inspection shall be instituted when 5 consecutive lots or batches have been considered acceptable on original inspection.
Normal to Reduced
When normal inspection is in effect, reduced inspection shall be instituted providing that all of the following conditions are satisfied:
The calculation of the switching score shall be initiated at the start of normal inspection unless otherwise specified by the responsible authority.
The switching score shall be set at zero at the start and updated following the inspection of each subsequent lot on original normal inspection.
Reduced to Normal
When reduced inspection is in effect, normal inspection shall be instituted if any of the following occur on original inspection:
ANSI/ASQ Z1.4-2003 and ISO 2859-1
If the cumulative number of lots not accepted in a sequence of consecutive lots on original tightened inspection reaches 5, the acceptance procedures of this part of ISO 2859 shall not be resumed until action has been taken by the supplier to improve the quality of the submitted product or service, and the responsible authority has agreed that this action is likely to be effective. Tightened inspection shall then be used.
In the event that 10 consecutive lots or batches remain on tightened inspection (or such other number as may be designated by the responsible authority) inspection under the provisions of this document should be discontinued pending action to improve the quality of submitted material.