platform secured to the eastern span of the bay bridge is a crucial components to keep the bridge from curoting. although the exterior is protected from the elements, interior leaks are a concern with critics. only on 2 ktvu's tom vacar takes us inside the bridge to show us how protection was built into the design many years ago. >> reporter: see this hanging from the eastern span of the bay bridge? it is one of several machines that protect the parts of the interior. that is because engineers are always concerned about water collecting and corroding. today we went inside the decks, and well into the causeway. in chambers dehumidifies protecting structures and equipment. in here the heart and soul of the bridge, the 17,000 strands that make up the cable, they are anything but exposed -- >> we have taken measures to have dehumidifiers, 5 of them, in different locations to keep the humidity down. grabs the moisture and blows it outside. >> reporter: minimizing moisture and low humidity is an excellent way to prevent corrosion, that is why airliners are stored in the desert and why this bridge at