An aseptic process simulation, or media fill, is the test that proves your aseptic process can fill product without contaminating it. Here is what Annex 1 expects, how to design it, and where fills go wrong.
It is a controlled test of your aseptic process. Instead of product, the line fills a sterile nutrient medium into your containers, running the same operators, equipment, and interventions as a real batch. The filled units are then incubated. If the medium stays clear, the process held. If it grows, contamination got in, and you need to know where.
Annex 1 treats APS as evidence that your aseptic process is under control. It expects the simulation to represent routine production closely, to include the worst-case interventions and conditions your process actually sees, and to be repeated on a defined schedule. The media fill program sits inside your wider contamination control strategy, not beside it.
Initial validation needs at least three consecutive successful simulations that together cover every shift the aseptic process runs on. After that, APS is normally repeated twice a year, roughly every six months, for each aseptic process, each filling line and each shift, and every operator should take part in at least one successful APS a year. The number of units must be enough to simulate every activity in the real process, with the number justified in your CCS. Annex 1 gives a typical minimum of 5,000 to 10,000 units, and for batches under 5,000 units, at least as many units as the production batch. The target is zero growth: any contaminated unit means the APS has failed.
The value is in the worst case. A media fill only proves what it simulates, so it must include the interventions, stoppages, shift changes, line speeds, and hold times your process really encounters, not an idealized run. Duration, container and closure handling, and incubation conditions all need to be justified. A fill designed to pass easily proves very little.
Most failures trace back to interventions: an operator reaching in, a stoppage handled badly, a gowning or behavior lapse. A single contaminated unit fails the simulation. Annex 1 then expects an investigation into the most probable root cause, corrective action, normally at least three consecutive successful repeat simulations, a review of every batch made since the last successful APS, and product from the affected line held in quarantine until the failure is resolved. The investigation matters as much as the result.
Yes. Media fills sit where aseptic filling and environmental monitoring meet, which is our ground. Damgaard Solutions provides named senior engineers who design and run APS programs, define the worst-case interventions, and close the investigation when a fill fails, all inside your contamination control strategy. Our engineers have delivered on GMP sites across Scandinavia.
You engage specific engineers by name before anyone sets foot in your facility, with no CV pools and no intake delays. Work is priced per signed milestone, not per hour, so the scope and the cost are clear from the start. We are part of Damgaard Group and based in Birkerød, near Copenhagen, working with GMP manufacturers across Europe.
Tell us where your media fill program stands and we will show you where the risk is. Get in touch through the Damgaard Solutions contact page to start a conversation.
Annex 1 contamination control strategy: what it must cover
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Sources retrieved September 2026. General guidance, not regulatory advice.