The drop down seal is hidden in the aluminium construction of PIU door leaf. This makes it completely invisible to the eye when the door is open.   The seal serves as a barrier that seals the room off, protecting it from air-flows, odours, light, sounds, dirt, dust, insects and even smoke and fire. In this way, PIU hidden door frame with the drop down seal also improves acoustic insulation (up to 35dB) and thermal insulation in a given room.

The high quality and durability of the seals is confirmed by certificates from renowned testing institutes, including IFT Rosenheim.