you are correct. according to ISO 8536-4 apparatus for intravenous infusion does require a particulate filter. The filter component exists in this design, however is not responsible for prevention of air entrainment merely the filtration of any solid matter. Note the graphics here are for understanding by a largely non technical audience hence omission of many design details. Use of a flexible seal as opposed to a filter mesh to prevent air entrainment has numerous advantages over a fine filter in clinical practice. It is not fluid dependant (Intrafix safeset can only be used to infuse crystalloid solutions, fine pore size means it would filter out components of blood products or some colloids such as gelofusine, hence room for potentially dangerous human error). The floating seal also provides visual feedback as to infusion state. I am happy to discuss this more pros and cons. you can leave your email here should you wish to discuss.

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ian