Single Wall Stacks Can Be Constructed Of Various Materials. Some Applications May Require Internal Coatings Or Linings. External Insulation And Lagging May Be Used To Keep Gas Temperatures From Dropping Below The Acid Dew Point Or For Other Thermal Considerations. Single Wall Stacks Can Be Grade Mounted Or Placed On The Outlet Of Equipment Such As A Fan, Economizer Or Scrubber. Single Wall Stacks Can Be Free Standing Or Braced.