A concise technical characteristic of a new low-background laboratory DULB-4900 of the BNO INR RAS is presented. The technique and the results of background measurements in the Hall, ordinary box and low-background box are presented. Rn-222 contamina
tion in the laboratory air has been measured by direct detection of gamma-radiation of its daughter Bi-214 distributed over the volume of the low-background box. The results of the data analysis are presented.
