Like all natural materials, natural stone contains trace natural radionuclides (radium-226, thorium-232, potassium-40). Chinese national standard GB 6566 "Limits of radionuclides in building materials" classifies decorative materials into Classes A, B and C using the internal exposure index (IRa) and external exposure index (Iy). Class A products may be produced, sold and used without restriction, including interior finishes of civil buildings. All HENGSHENG MARBLE natural stone is tested to this standard.
The internal exposure index IRa reflects the effect of radon released by radium-226 decay on indoor air; Class A requires IRa at or below 1.0. The external exposure index Iy reflects gamma radiation emitted by the stone itself; Class A requires Iy at or below 1.3. Both must be met for Class A.
Class A may be used anywhere, including residential interiors. Class B may not be used for interior finishes in residential buildings, hospitals or schools, but may be used for external walls and other buildings. Class C is limited to exterior finishes and outdoor uses. Always request a test report when purchasing.
Hong Kong projects and renovations commonly reference GB 6566 or equivalent standards. Interior works in homes, schools, hospitals and offices should specify Class A material, with test reports written into the contract; cladding and external components follow project requirements.
Request a radioactivity test report for the relevant batch with your order. The report should state variety, batch, IRa and Iy values and the testing body. We can also supply complete technical documentation to support estate applications and handover inspection.
Natural stone contains extremely small amounts of natural radionuclides. Products meeting GB 6566 Class A are safe for unrestricted interior use. Requesting a test report is the practical check when buying.
Class A can be used indoors in homes, hospitals and schools. Class B cannot, but may be used on external walls and non-civil buildings. Class C is for exterior and outdoor use only.
Yes. Request a radioactivity test report for the relevant batch with your order; we can also supply technical documents to support estate applications and project handover.