A switch comprising a first contact on a support surface, a switch housing sealingly secured to the support surface around the first contact to form a hermetically sealed chamber about the first contact, and a second contact movable in the chamber towards and away from the first contact, wherein the support surface is provided on a support having two or more protrusions protruding from the support surface and received in apertures formed in the switch housing to locate the switch housing relative to the first contact.