CEHT and DEHT study

How to carry out Clean equipment hold time study in a pharmaceutical manufacturing faclity( formulation)? Is is required to take swab for active along with micro for the study period?

How to carry out dirty equipment hold time study in a pharmaceutical manufacturing faclity( formulation)? How to make a sampling plan for this ?

Dear Panda,

In my opininon if the cleaning validation is already done, then there is no need to perform the swab for active again. We performed swab for MLT immediately after cleaning and after holding the equipment in the area for the proposed hold period. Also we performed check for visually clean acceptance criteria immediately after cleaning and after hold for the proposed period.

In case of DEHT ,We performed check for bioburden , check for impurties after storage of the dirty equipment for the proposed hold time. Also here we established that the dirty equipment can be cleaned as per the same procedure specified in the cleaning sop after storage for the proposed period



Dear Mr. Tapan Kumar Panda,

Please check following references to understand more about CEHT and DEHT studies.


  • Richard J. Forsyth, “Equipment Hold-Time for Cleaning Validation,” April 1, 2008; Pharmaceutical Technology ( http://pharmtech.findpharma.com/pharmtech/Peer-Reviewed+Research/Equipment-Hold-Time-for-Cleaning-Validation/ArticleStandard/Article/detail/505369 )
  • T. Fugate, "Hold Time Studies: A Lost Parameter for Cleaning Validation," Journal of Validation Technology, 13 (3), 206-209, 2007.
  • GXPandJVT.com Forums, “Cleaning validation equipment hold time,” ( http://www.gxpandjvt.com/forum/forum_posts.asp?TID=115&PN=2&get=last )
  • Joseph Pickett, “Dirty equipment holding time high risk with water left on equipment,” Validation Times, June, 2007 ( http://findarticles.com/p/articles/mi_hb5677/is_6_9/ai_n29411135/ ) Please don't forget to feedback.
  • Dear Tapan Kumar Panda,

    not much to add to the above references. As a general rule, after DEHT look for actives and degradation product, focusing on sticky, hygroscopic products, and equipment for wet or humid processing where caking is to be expected. CEHT is of microbiological concern.

    One issue, which came up during a recent inspection, is the storage of the equipment. Although we have validated a DEHT of seven days, the inspectors did not accept that time. Their concern was that equipment stored dirty (in the dirty equipment storage area), even covered with stretch film, poses a cross contamination risk between stored dirty equipment, potentially passing the cleaning validation looking for one active but potentially contaminated with another active from neighbouring equipment, not considered in the cleaning validation. Although the risk seems low and the whole issue an “inspectional overshoot”, we are now forced to clean the equipment immediately after use, and a DEHT of more than 24 hours is to be treated as a deviation and includes extensive sampling after cleaning, and equipment quarantine until approval.

    Best regards