A method of processing materials at multiple work sites that prevents contamination of the atmosphere. The method includes providing a plurality of work sites containing workpieces, positioning a track connecting the sites, providing a mobile system comprising an enclosure and a treatment system in communication with a space enclosed by the enclosure, moving the mobile system so that the enclosure surrounds the workpieces on the first site, processing those workpieces, moving the mobile system along the track as a single unit onto a second work site, and processing those workpieces on the second site. The enclosure may be readily openable at opposing portions facing the track to enable the enclosure to pass over workpieces on the plurality of work sites. Additionally, a method of constructing an operation for processing workpieces is provided.