--------I   I------------I
        I       I   I            I---------
        I       I   I------------I---------
        I       I    <- Air <- <- <- <- <-
        I       I   I------------I---------
        I       I   I            I---------
        --------I   I------------I
            ^     ^     ^
            I    Gap    I
            I              I
       Electrode    Electrode