The nappies external ventilation layer is made of a special material that can lock in pee while releasing heat and humidity. The entire layer is covered with tiny holes that are invisible to the naked eye. These holes allow gases like water vapour to pass through, but completely block the passage for liquids like pee. So when the exterior of the nappy feels damp, it is not due to the leakage of pee, but the heat and humidity that have been released. Sometimes it may also have the smell of the baby's pee or poo. By increasing the nappies breathability and preventing humidity, your baby will feel dry and comfortable for a longer time!