ISO 11665-1:2012 outlines guidance for measuring radon-222 activity concentration and the potential alpha energy concentration of its short-lived decay products in the air. The measurement methods fall into three categories: spot measurement methods; continuous measurement methods; integrated measurement methods. ISO 11665-1:2012 provides several methods commonly used for measuring radon-222 and its short-lived decay products in air. ISO 11665-1:2012 also provides guidance on the determination of the inherent uncertainty linked to the measurement methods described in its different parts.