The Church of the Holy Sepulchre in Jerusalem is a major pilgrimage site for Christians around the world. Every day thousands of sticks of incense, candles and torches are burnt in ceremonies and processions under its once golden dome, which had become blackened over centuries. The mechanical ventilation system not only supplements the natural ventilation but also protects the restored gold-leaf ceiling decorations for future worshippers to experience the church in its full glory. To limit discolouration, an advanced laminar flow system was designed using the Coandă effect to pass clean air over the ceiling, forming a boundary level between the gold leaf and the smoke-laden air. To achieve this, small air-handling units were concealed in the structure around the perimeter of the dome, discharging smoke along with clean air at the oculus.