Radon in the workplace--a study of occupational exposure in BT underground structures.

During the period August 1993-October 1994 a study was undertaken throughout British Telecommunications plc to assess occupational exposure to radon. This paper is concerned only with that portion of the work concerned with underground structures. The results show that radon can build up to very high concentrations in manholes and implies a significant risk to those who need to work in them. For various reasons, which are explained, exposures are much less than predicted and in all but a very few cases the annual predicted radiation dose due to radon is expected to be below 5 milliSieverts (mSv). A safe system of work is described which seeks to ensure that no BT people receive an annual radiation dose of greater than 5 mSv as a result of occupational exposure to radon.