(a) Normal, tightened and reduced on-line sampling plans are specified in §42.132 (Determining cumulative sum values). Normal plans shall be used except when the history of inspection permits reduced inspection or requires tightened inspection.

(b) Switching rules: Normal on-line inspection procedures shall be followed except when conditions in paragraph (b) (1) or (3) of this section are applicable or unless otherwise specified. Application of the following switching rules will be restricted to the inspection of production for one applicant at a single production location and will be based upon records of original inspections of production (excluding resubmitted portions previously rejected and reworked) at that same location.

(1) Normal inspection to reduced inspection. When normal inspection is in effect, reduced inspection shall be instituted provided that reduced inspection is considered desirable by the Administrator and further provided that all of the following conditions are satisfied for each class of defect:

(i) The preceding 40 consecutive portions of production have been on normal inspection and no more than one of these portions has been rejected on original inspection; and

(ii) The total number of defects in the subgroups (1000 sample units) from these preceding 40 consecutive portions of production is less than or equal to the following limit numbers for the specified AQL's:

(2) Reduced inspection to normal inspection. When reduced inspection is in effect, normal inspection shall be reinstituted if any of the following occurs:

(i) More than one portion of production in any 40 consecutive portions of production is rejected on original inspection; or

(ii) Production becomes irregular (delayed or accelerated); or

(iii) Other valid conditions warrant that normal inspection shall be reinstituted.

(3) Normal inspection to tightened inspection. When normal inspection is in effect, tightened inspection shall be instituted when two out of five consecutive portions of production have been rejected.

(4) Tightened inspection to normal inspection. When tightened inspection is in effect, normal inspection shall be reinstituted when five consecutive portions of production have been considered acceptable.

(c) When the rules require a switch in the inspection status because of one or more classes of defects, all classes of defects shall be inspected under the new inspection criteria. At the option of the user of the service, and when approved by the Administrator, such user may elect to remain on normal inspection when qualified for reduced inspection, or on tightened inspection when qualified for normal inspection.