IEMs with dynamic driver don't necessarily need to have a vent in the housing, though many have, which mainly expands the sounstage. Some IEMs with dynamic drivers like the UE200 or Shure SE215 have got completely closed shells with out any vent and therefore a good isolation.
Though the Carbo Tenore is vented, to me its isolation is above average but below closed IEMs. In my ears, soundstage is rather on the small side.
An interesting thing I have noticed about the Carbo Tenore is that their tonality varies with insertion depth from a v-shaped sound (with a good amount of sub bass that doesn't affect upper bass, ground tone or mids wherefore the lows remind me somehow of the SE846 which sounds kind of similar in the lower regions) at regular insertion, to a darkish sound signature with recessed highs, warm mids and more emphasised ground tone when inserted deeply.
Though it may offer a good value for its price, in my honest opinion it can't really compete against the ER-4S which is on another level in terms of resolution, soundstage and instrument separation, what you will especially notice when playing more complex music with many instruments/sounds and fast attack in the bass. But that's just my perception.