The requirements of this part of IEC 61577 are applicable to instruments for measuring airborne radon volume activity. This part is applicable to instruments used to measure radon in work places, in dwellings, outdoors and in soil. The method of measurement depends on the exact objective but the requirements are for general purpose instruments to be used for radiological protection or research applications. This standard applies to all types of radon measuring instruments that are based on grab sampling, continuous and integrated methods. The activity can be measured continuously by pumping or by diffusing the air containing radon into the detector or at a particular moment by measuring the activity of an air sample (grab sampling). The purpose of this part of IEC 61577 is to specify the main performance characteristics of instruments intended for measurement of airborne radon volume activity, their specific method of testing and documentation requirements. This part is to be used with IEC 61577-1.