The first section of the Forth Road Bridge's new dehumidification system has been switched on, in a bid to extend the life of the crossing.
Dehumidification equipment has been installed on the west cable
It is the first time the work has been carried out on such a structure in the UK.
Very dry air is now being pumped through about a quarter of the bridge's two main suspension cables.
The aim is to prevent further corrosion occurring by reducing the humidity within the cables to below 40%.
Since April last year contractor, C Spencer, has been wrapping the westernmost cable between the two main towers in an airtight neoprene membrane.
Bridge operator's Forth Estuary Transport Authority (Feta) maintenance workers have installed several miles of ductwork to accommodate electrical wiring.
The first of three dehumidification plants has now been connected to the system.
Feta convener Tony Martin, said: "I'm very pleased with how the dehumidification project is going.
"Work is progressing on schedule and Friday's switch-on marks an important milestone.
"The full system will not be up and running until late 2009, and we will then need to give it about 18 months to work before we can measure how effective it has been.
"However, I'm confident that we've given ourselves the best possible chance of success."