Cleaning validation answers a simple question with serious consequences: after you clean a piece of shared equipment, is what is left behind safe for the next product? For years the industry answered it with rules of thumb. That has changed, and many cleaning programmes have not caught up.
From rules of thumb to health-based limits
The old limits were familiar: no more than one thousandth of the normal dose of one product carried into the next, or no more than ten parts per million. They were easy to calculate and easy to defend because everyone used them.
The EMA guideline on setting health-based exposure limits, in use since 2015, moved the basis to toxicology. Each product gets a permitted daily exposure, set by a qualified toxicologist from the available data, and carryover limits are calculated from it. Annex 15 now refers to this approach directly. The result is limits that are sometimes tighter than the old ones and sometimes much looser, but always grounded in what the residue can actually do to a patient.
What a cleaning validation programme needs
- A health-based exposure limit for each product made on shared equipment, with the toxicology assessment behind it.
- Equipment surface areas and the hardest-to-clean locations, identified rather than assumed.
- A worst-case approach that groups products and equipment sensibly, so you do not validate every combination.
- Sampling methods, swab and rinse, with recovery studies showing how much residue the method actually picks up.
- Analytical methods validated at the levels you need to detect.
- Limits for cleaning agents and microbial contamination as well as product residue.
Worst case, chosen honestly
Grouping is where cleaning programmes save the most effort and where they are most often challenged. The worst-case product is usually the one hardest to clean, least soluble or most potent, but the reasoning has to be written down and should use data rather than opinion. Inspectors will ask why this product represents the others, and they will check whether a new product introduced since was assessed against the choice.
Visual inspection and dirty hold times
Visually clean is still expected as a minimum, and where limits allow, it can do more of the work, provided the people inspecting are trained and the visible limit has been established. Two time limits also need evidence: how long equipment can sit dirty before cleaning, and how long it stays clean before use. Both are easy to forget until a schedule slips.
Keeping it validated
Cleaning validation is not a one-off study. New products, changed formulations, new equipment and changes to cleaning agents or procedures all need assessment against the existing programme. Ongoing monitoring, through routine sampling or trending of verification results, shows the process stays in control between formal studies.
The most common weakness is not the original study. It is a programme that was right five years ago and has not been reassessed against the products now running. Cleaning validation sits alongside equipment qualification, and both depend on knowing exactly what equipment you have and how it is used.
Where to go next
Explore GxP Copilot for AI-native validation, TraceDraft for source-traceable clinical documentation, or book a demo to see either on your own data.