I (Jim) have never seen a completely enclosed forming section.  Yes, gap formers come close, but even they are exposed to the atmosphere.

One can argue that the entire machine room is a controlled atmosphere, but we know there is a great deal of variability within the machine room, especially seasonally.

Pressure washers in the pulp mill were designed years ago to address this problem.

Perhaps the issue is that "we have never done it that way."  Perhaps papermakers still think they need to walk up and look at the wire...  They can't do that on a gap former now.

What about fully enclosing the forming section and tightly controlling the atmosphere?  Any experiences or knowledge out there?