Once the ducting has been brought from the boundary the next step is to bring it into the property via an external
gas trap. Black ducting which is resistant to light damage is used up to the gas trap then special white ducting,
which does not give off toxic fumes when burnt and so is safe to use inside a building, continues through the external
wall and eventually ends at the router backplate.
Sometimes the internal route can involve taking the white ducting a fair way through a property.