Abstract: An apparatus is disclosed for coating an article with a coating material by vapor deposition wherein an improved deposition chamber having a base and a cover is employed. The cover of the deposition chamber is removable and interchangeable with other deposition chamber covers which have different sizes and geometries. By changing the covers, the inner surface area of the deposition chamber cover can be adjusted to accommodate the surface area of the articles to be coated. Thus, it is possible to avoid loses of parylene which can coat on the inner surface of the deposition chamber during the parylene coating process. A vapor deposition apparatus providing a generally upward flow pattern of parylene monomer is also disclosed.