Sterile system and method for filtering biological or medical liquids, especially blood or blood constituents

A method for the filtration of a fluid with a sterile filtering system comprising a filter including a housing, wherein the housing is divided by a filter material into a first chamber and a second chamber, wherein the first chamber includes a first chamber inlet and the second chamber includes an aeration connection and a second chamber outlet;

• a first collecting line for the feeding of fluid to be filtered, the first collecting line being connected to the first chamber inlet;
• a collecting container including a collecting container inlet;
• a second collecting line which connects the second chamber outlet to the collecting container inlet;
• a means for opening or closing the second collecting line;
• a collapsible container including a first air inlet or outlet line and a second air inlet or outlet line, wherein the first air inlet or outlet line is fluidly connected to the first chamber inlet of the first chamber, and the second air inlet or outlet line is fluidly connected to the aeration connection of the second chamber;
• and
• a means for opening or closing the second air inlet or outlet line;
• wherein the first air inlet or outlet line is closed by a hydrophobic membrane or a non-return valve that allows a passage of fluid only out of the collapsible container;
• wherein the second air inlet or outlet line does not include a hydrophobic membrane;
• and
• wherein the volume of the collapsible container is dimensioned such that when the first collecting line, the first chamber, the second chamber, and the section of the second collecting line upstream of the means for opening or closing the second collecting line are filled with the fluid to be filtered, the displaced air remains in the collapsible container;
• the method comprising:
• closing the means for opening or closing the second collecting line, and opening the means for opening or closing the second air inlet or outlet line;
• conveying the fluid to be filtered through the first collecting line, the first chamber, the filter material and into the second chamber, thereby displacing air into the collapsible container;
• closing the means for opening or closing the second air inlet or outlet line, and opening the means for opening or closing the second collecting line;
• conveying the fluid through the first collecting line, the first chamber, the filter material, the second chamber, the second collecting line, and into the collecting container;
• and
• opening the means for opening or closing the second air inlet or outlet line, such that the air collected in the collapsible container is conveyed back into the second chamber via the second air inlet or outlet line.