What is Poison Test for Inspectors

“Quality does not come from inspection but improvement of the production process” — W Edwards Deming       


When the Devas and Asuras started the Samudra Manthan (Churning of the ocean for the celestial nectar), before the precious gems and Amrit, foremost the poison oozed out of the ocean. The poison was so dangerous and powerful, just mere contact with the poison made few asuras lose their lives, and all the Devas fainted and started to get perishable. Then everyone requested the Mahadev, to save the entire universe from getting extinct from the poison.

It is said that any problem can be solved with the help of the team. If a Problem is as dangerous as ‘poison’, then also a team can solve it easily.


There is a tendency in the quality management field to confuse the root cause of a problem with the problem’s real cause. A root cause is objective evidence of a quality problem. The real cause of a quality problem, however, is the actual finding or a nonconformance.

Uncovering real causes of quality problems requires different, deeper scrutiny than identifying root causes. The purpose of the Poison Test is to uncover the true potential of the inspector who is conducting incoming, in-process and final inspection so that only the qualified and competent inspector can be planned for the inspection process.

Read More: https://bit.ly/Step1DefineProblem

Definitions (ISO 9000: 2015):

       Nonconformity (clause 3.6.9): Nonfulfillment of a requirement

       Defect (clause 3.6.10): Nonconformity related to an intended or specified use

       Inspection (clause 3.11.7): Determination of conformity to specified requirements

Read More: https://bit.ly/ProblemSolvingTechnique

Detailed Information:

The goal of any manufacturing-based organization is to have, amongst other things, proper product quality control. A quality issue is a defect, deficiency, or a significant variation in a product’s expected appearance or performance. A quality action is a necessary activity required to mitigate a quality issue and prevent its further occurrences. 

What is Poison Test?

In many cases, quality assurance inspectors come up with inconsistent visual inspection results because they either do not completely understand defect specifications or have no references to compare the product with. The organization should reach a consensus on defect specifications and clearly defined defect criteria to enable inspectors to accurately make pass/fail decisions for products.

Quality managers should regularly assess the performance of the current inspection process to confirm the consistency of inspectors’ pass/fail decisions and determine how well the inspectors’ decisions match the established defect criteria to standardize visual inspection performance in the organization.

When inspectors’ decisions on the same products contradict the visual inspection, the organization should address the issue by analyzing the most significant visual defects. Evaluate the cost of quality by time to repair, importance to the customer frequency and defect count to identify which defect type has the greatest impact on daily operations and implement effective action plans.

Read More: https://bit.ly/RootCauseAnalysis3L5Y

Purpose of Poison Test

  • To ensure inspectors at all stages (Incoming, In-process, Final Inspection) meets the specification & required standards are defined
  • To test if inspectors can identify all defective parts mixed with ok parts. Hence, it is a periodic test for the inspector’s qualification

How to conduct the study?

  • Arrange 20 parts with 15 Good and 5 parts Not Good (quantity may vary) and mix them.
  • Give these 20 parts to visual/dimensional checking inspectors to segregate the defective part (Inspector should be unaware of the process)
  • Observe appraisee segregating parts
  • Verify the parts after the segregation and record them in the poison test report
  • If the appraiser doesn’t find all 5 defective parts, then provide training and again test
  • Do poison test for all visual & Dimensional inspectors periodically/for new inspectors before deputing them to the inspection stage

Read More: https://bit.ly/IshikawaDiagram

Frequency for the Poison Test

Depending upon the criticality of the process and product, the organization can define the frequency. Apart from the result of the Poison Test, the organization should also monitor the Defect Escape Rate (feedback from PDI and Customer).

  • Weekly
  • Monthly
  • Quarterly
  • 6 Monthly
  • Annually

Read More: https://bit.ly/7ProblemSolvingTechnique

Benefits of Poison Test

  • Reliability of the inspection process
  • Improved competence of the inspectors
  • Reduction in internal and external rejection
  • Enhanced customer satisfaction

Key Industry Challenges:

  • How often does the organization feel confident about the competence of inspectors after poison test qualification?
  • How often poison tests are conducted and only reports are not prepared?
  • How often the competence of the inspectors is monitored periodically by using poison tests and other methods?

Read More: https://bit.ly/CausalFactor


IATF 16949: 2016

ISO 9001: 2015

ISO 9000: 2015

Industry Experts

This is the 151st article of this Quality Management series. Every weekend, you will find useful information that will make your Management System journey Productive. Please share it with your colleagues too.

In the words of Albert Einstein, “The important thing is never to stop questioning.” I invite you to ask anything about the above subject. Questions and answers are the lifeblood of learning, and we are all learning. I will answer all questions to the best of my ability and promise to keep personal information confidential.

Your genuine feedback and response are extremely valuable. Please suggest topics for the coming weeks.

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Yogesh Kumar
Yogesh Kumar
1 year ago