As gases, each of these is the only member of its family's decay chain
that can percolate from its source in rocks or soil through cracks into a building.
Included in these changes are: new code architecture; incorporation of numerical solvers for the calculation of radioactive decay chains
(including the in-growth of decay products during air transport and ground surface deposition); enhanced error messages; updated online help and a utility for migrating version 3 datasets, wind files and population files to version 4.
In the decay chains
, both a previously unknown alpha-decay pathway in Db-270 (dubnium - element 105) and the new isotope Lr-266 (lawrencium - element 103) were identified.