Possible Causes of Out of Specification

Out of specification is the deviation of the product from the pre-determined specification. It means when a product is unable to meet the predefined limits for that particular product. There are various possibilities that may be responsible for these deviations.

These possible causes of the out of specification can be divided into two parts. First is analytical error where a product doesn’t have any defect but it has a problem in its analysis and the other one is a manufacturing defect in the product where analysis is correct but the product actually has a problem. The following are the possible causes for out of specification results.

1. Test analysis error in QC lab
2. Lab equipment malfunctioning
3. Production equipment malfunctioning
4. Operator/human errors in manufacturing

1. Test Analysis Error in QC Lab: Error in the QC lab is human or analyst error. This is the most probable cause of the OOS and should be investigated first during the investigation of OOS. There are many areas where errors may possible. During the analysis of the product, there may be an error during the handling of the sample or standard. There may be an error in sample weighing and its dilution. Errors are also possible in chromatography and titration or even in the calculation.

2. Lab Equipment Malfunctioning: Due to this problem analysis is also unaware of the occurrence of this error. Sometimes equipment or instrument is not calibrated at the due date and it shows the incorrect results due to which product results deviate the limits. While in some other cases it happens due to malfunctioning of the equipment or instrument used in the analysis.

3. Production Equipment Malfunctioning: This causes the actual defect in the manufactured product. An out of specification is observed when there is any problem with manufacturing equipment and a faulty product is produced. Malfunctioning of equipment may include errors in timers or any other part of the equipment that is not noticed during the manufacturing process.

4. Operator/Human Errors in Manufacturing: Operators play an important role in the manufacturing of quality products. A wrong timer setting for any production activity, wrong sieve or screen used, a wrong process followed, any manufacturing process skipped or anything like this may cause a serious problem in manufactured batch. It is happed when the operator doesn’t follow the instruction given in the batch manufacturing record. It is always very difficult to find a human error responsible for out of specification results because it is a human tendency to hide the errors done by him and sometimes it is done unknowingly and found correct in documents.

During manufacturing, many process steps are followed and any fault may cause a defect in manufacturing the product therefore, careful handling of material and equipment is required. Above mentioned points can help you to investigate the root cause of an out of specification easily.