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Suppliers of cell lines and raw material should conduct extensive testing before releasing a product, and provide documentation listing what tests were done, and indicate the level of sterility. One thing to note is that sterility assurance levels (SAL) may vary by manufacturer or product. SAL is the probability of one random contaminant occurring on a surface after sterilization and it is expressed as 10-n. Example: SAL 10-3 means that there is a probability of 1 contaminated product out of 1,000. That being said, if you have extremely sensitive cells and/or assays, you may choose to filter sterilize your media prior to use. No further testing should be required. However, some laboratories may need have more stringent guidelines and testing should be tailored to those more extensive needs. Our suggestion is to always contact the supplier for more information or clarity about the tests that were performed on the product supplied Note: If you have specific concerns about a media or reagent, it is good practice to make the manufacturer aware of the potential issue so they can conduct the appropriate quality investigation.