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.