The QC water filters are designed to prevent particulates; they should not allow particles larger than how many microns?

• A. 10 microns
• B. 25 microns
• C. 50 microns
• D. 100 microns

Answer: (B)

Filtration ratings specify the largest particle size a filter will block. For QC water used in radiology, you want to stop debris big enough to cause clogs, streaks, or artifacts, while still allowing water to flow smoothly. A 25-micron filter is designed to trap particles larger than 25 microns, letting smaller particles pass. This provides effective protection against noticeable particulates without the drawbacks of an overly fine filter. Using a finer filter (like 10 microns) would further reduce particulates but can reduce flow and increase cost, while a coarser filter (50 or 100 microns) would let larger debris through, defeating the purpose. Therefore, preventing particles larger than 25 microns is the appropriate standard.