Which ISO class has the most stringent particle limit for sterile compounding?

ISO Class 5 has the most stringent particle limit for sterile compounding because it ensures that the environment in which sterile products are prepared is as free from contaminants as possible. Specifically, ISO Class 5 permits a maximum of 3,520 particles per cubic meter for particles 0.5 microns and larger, which is essential for areas where aseptic manipulations occur, such as laminar flow hoods.

In sterile compounding, maintaining an environment with low particulate levels is critical for patient safety, reducing the risk of contamination that could lead to infections or other complications. The lower the ISO classification number, the cleaner the air must be, hence ISO Class 5 is the standard used for direct compounding areas.