SCOPE: This standard specifies procedures, minimum requirements and general guidance for measurement of radon and radon decay product concentrations in Multifamily buildings comprised of more than three attached dwellings. THIS DOCUMENT INCLUDES: 1) Introduction to Radon. 2) Introductory Guidance for Residence Managers. 3) Protocol for Conducting Radon and Radon Decay Product Measurements in Multifamily Buildings: Specific testing protocols that include instructions on where to test, strategies for conducting reliable tests, reporting and associated quality control measures.