The e!ects of covering materials on indoor Rn concentrations in o$ces in Hong Kong

The variation of Rn concentrations in 134 o$ces with di!erent covering materials cladded on internal building surfaces, including walls, ceilings and #oors, were measured. The three commonest combinations (87 sites) of covering materials for the walls, ceilings and #oors in Hong Kong are (A): wall paper, "bre board, carpet; (B): paint, paint and plastic tile and (C): paint, "bre board, plastic tile. The average Rn concentrations for combinations (A) and (B) were about the same, while that for combination (C) was signi"cantly lower than those for (A) and (B). A person working in an o$ce with combination (C) can receive an average annual tracheobronchial equivalent dose smaller than one working in an o$ce with combinations (A) and (B) by an amount as large as 0.8 mSv. ( 1999 Elsevier Science Ltd. All rights reserved.