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Areas to Filter in a Pharmaceutical Process

By Richard Juskowiak, Donaldson Process Filtration

Pharmaceutical manufacturing requires filtration at multiple points in the process. Whether the product is a liquid or solid dose product, it can be contaminated by impurities in the gas, compressed air, steam, and liquid used in the process. Contaminants may include moisture, oil, debris, and bio-burden.

To reduce time and costs, aim to capture impurities early in the process. Build-in redundancies that make contamination sources easier to isolate. Once bacteria growth surfaces downstream, it is arduous and expensive to track down the source and recertify your process to run again.

With those principles in mind, here are critical areas to filter:

Utility Room

Start filtration in the utility and storage area; here, your facility brings in municipal or well water, generates steam, and makes or stores compressed air and nitrogen. Plan to use pre-filtration on each of these “utilities” before it enters your process. Pre-filtration here improves the efficiency and longevity of your finer filters downstream.

For water, a 5-micron liquid element will remove forms of particulate larger than 5 microns in diameter, providing an acceptable level of clean supply water for your steam-in-place (SIP) or clean-in-place (CIP) processes. (Ingredient water will require additional reverse osmosis or micro-filtration later in the process).

If you use nitrogen, changing tanks can expose the open line to airborne contaminants, such as dirt, dust, or microorganisms. A pre-filter on the nitrogen line is also a wise precaution to ensure your nitrogen is free of impurities.

Formulation Tanks

The area where active pharmaceutical ingredients (APIs) are formulated and stored should be another focus of filtration. Steel tanks can be a breeding ground for bacteria introduced by personnel and ambient air.

Injecting a blanket of clean dry air or nitrogen around the APIs a recommended practice; it also equalizes air pressure as tanks are emptied and filled. Blanket air and nitrogen should be filtered with a 0.2 micron filter on your nitrogen or air injection equipment to remove moisture and impurities. Nitrogen can’t harbor organisms, but it can transport microscopic particles picked up in your piping.

Intermediate Fill Area

Wherever you introduce a new substance into your process, new opportunities for impurities occur. This includes the intermediate fill area, where APIs are mixed with other ingredients such as coatings or binding agents to formulate the final product.

Here, fine micron point-of-use filters should be placed on all lines of steam, water, or compressed air that come into contact with ingredients, or with surfaces that ingredients touch. For water and liquid chemical applications, filters can be 1 to 0.2 microns, while high-purity air might require a filter of up to 0.03 micron.

Mixed formulations may be stored in another set tanks just before encapsulation or bottling. Another set of nitrogen or CDA buffers and point-of-use filters should be used on these storage tanks.


Packaging materials can often pick up impurities during storage or transport. For aseptic pharmaceutical packaging, it is good practice to clean liquid containers with culinary-grade steam before filling. Foil or plastic seal material should also be blasted with steam and dried with filtered compressed air to prevent microbes from multiplying in a finished product. Culinary-grade steam requires the removal of 95 percent of particles 2 microns in size or larger.

Benefits of Redundancy

While these steps may appear redundant, filtering air, water, and steam at multiple stages provides several benefits:

  • Pre-filtering saves costs by preventing overloads on more expensive elements downstream; 
  • Intermediate filtering reduces contaminants, such as flaking metal, potentially introduced by the process itself; and 
  • Fine-micron filters at the last stage of processing and packaging provide extra assurance of an aseptic process. 

In short, redundant filtration helps minimize risk and produce pure products at a lower cost.


Every processing facility is different and poses unique questions about filtration: What's the right micron size and filter efficiency at a certain location? How many CIP and SIP sterilization cycles can an element tolerate? What are the differences among various filter media?

A reputable filtration company will know the answers—especially one with pharmaceutical experience, like Donaldson. Working with you, we will help formulate a filtration plan that protects your product and process in the most cost-effective way. 

Have more questions about how our products benefit your business?

Richard Juskowiak is Product Support Specialist at Donaldson Company, Inc., in the process filtration group. He identifies technical solutions required by processors and works with engineers to introduce solutions for challenging applications.