Active pressure monitoring closure

An umbrella valve, comprising:

• an umbrella valve body (150) extending along a longitudinal axis;
• a diaphragm (225) extending outwards away from the longitudinal axis and along the longitudinal axis towards a proximal end of the umbrella valve body;
• and,
• a retention module (220) disposed on the umbrella valve body and configured such that, when the umbrella valve body is disposed through an aperture in a surface such that the retention module is disposed at least partially on a first side of the surface and the umbrella valve is on an opposite side of the surface, the retention module engages the first side of the surface to resist the diaphragm retracting the umbrella valve body through the aperture,
• wherein:
• an outer circumference of the diaphragm defines a perimeter in a first plane, and, in a non-deployed mode, the retention module is resting above the first plane such that, in a deployed mode in which the retention module engages the first side of the surface, the umbrella valve is preloaded with a predetermined tension.