dead air

noun3

1. •
   An unintended interruption in a broadcast during which nothing is transmitted: a silent period on radio or a silent period with no picture on television.

   • They fired the production engineer because too many moments of dead air were interrupting the broadcast.
2. •
   A quiet or awkward moment in a conversation where neither individual is speaking.

   • Today we're going to try sitting with silence a bit. Don't worry about any moments of dead air in the conversation.
3. •
   Air that is subject to little or no ventilation, thus, little to no air exchange.

   • Sealing up the house so perfectly, without planning for any active ventilation to replace the passive ventilation that you have eliminated, is not a good idea, because it encourages pockets of dead air. If you're going to seal it up so tight, then you need to plan for active ventilation through a filter, rather than no ventilation at all.