NEN-EN 13598-1 specifies the definitions and requirements for ancillary fittings and shallow chambers installed underground in non-pressure drainage and sewerage systems and manufactured from unplasticized poly(vinyl chloride) (PVC-U), polypropylene (PP), polypropylene with mineral modifier (PP-MD) or polyethylene (PE) intended for use for:- non-pressure underground drainage and sewerage outside the building structure (application area code “U”), and- non-pressure underground drainage and sewerage for both buried in ground within the building structure (application area code “D”) and outside the building structure.