When a key is pressed in a membrane switch, the air pressure within the switch cavity increases. In order for the switch to close properly, air within
a switch cavity must be displaced, equalizing the internal pressure. There are two standard venting methods that can solve this issue:
Designing narrow channels between key location cutouts (in the spacer layer) allowing the air from one key to move to another key locatoin when that key is pressed.
Similar to internal venting, narrow channels between keys are cut into the spacer layer. These channels then exit through the sides, rear, or internal cut-outs of the membrane switch. External venting is not recommended for membrane switches exposed to harsh environments, as there is a greater risk of contamination.