Filter device

A filter device, comprising:

• a case having a substantially bottomed tubular shape with an open upper end;
• a filter element having a substantially cylindrical shape provided inside the case;
• a lid body provided on the case so as to cover the upper end of the case;
• and
• an inflow portion and an outflow portion provided in the case, the inflow portion and the outflow portion communicating between an internal space and an external space of the case;
• and
• a detector that detects an environmental parameter,
• wherein:
• the lid body includes a flange portion and a cover, the flange portion having a substantially cylindrical shape is fixed to the case, and the cover having a substantially plate shape is provided on an upper side of the flange portion so as to cover a hollow portion of the flange portion;
• the cover is detachably provided to the flange portion,
• the flange portion has a first hole;
• the cover has a second hole;
• the first hole and the second hole communicate between the space inside the case and the space outside the case;
• the flange portion is sandwiched between the cover and the case;
• and
• the flange portion has a third hole opened in a direction along a plane perpendicular to a central axis of the case having a substantially bottomed tubular shape, the detector being inserted in the direction into the third hole.