Negative pressure backflow prevention apparatus

A negative pressure backflow prevention apparatus, comprising:

• a base having one end formed of at least one air inlet, a supporting portion having a proximal end mounted to the base and extending from the base in a given direction to define an opposite distal end, and a first connecting portion arranged at predefined locations of the base;
• the at least one air inlet penetrating into another end of the base to define an inlet opening;
• and
• a sealing member having one end formed of a second connecting portion and another end formed of an air outlet;
• the second connecting portion and the first connecting portion connected to each other in order to seal said another end of the air inlet;
• and the supporting portion penetrating through the air outlet;
• wherein the sealing member comprises an intermediate section extending from the second connecting portion in a direction toward and jointing with the air outlet such that the air outlet is supported by the intermediate section to selectively engage with the distal end of the supporting portion and wherein the intermediate section is kept consistently away from the supporting portion between the proximal end and the distal end of the supporting portion to define an internal hollow space inside the sealing member for receiving an ingress flow of fluid through the inlet opening.