This document specifies methods to be used for testing of air-to-air heat recovery components (HRC). The main purpose of the HRC is to exchange heat between exhaust air and supply air in order to save energy, which results in preheat or heat, and/or precool or cool supply air in ventilation systems or air conditioning systems. Optionally HRC can exchange air humidity between exhaust and supply air. The HRC contains the heat exchangers and all necessary features and auxiliary devices for the exchange of sensible heat and (if available) air humidity between exhaust air and supply air. The HRC will be installed in casings or ducts. If fans are part of the test unit, the effect of the fan power on the measured values will be corrected. This document specifies procedures and input criteria required for tests to determine the performance of a HRC at one or several test conditions, each of them with continuous and stationary air flows, air temperatures and humidities at both inlet sides. Three different test types are covered: Test type A, Laboratory testing of HRC installed in test casings (A1) or a HRC sections (A2); Test type B, Laboratory testing of HRC installed in non-residential ventilation units1 in design configuration; Test type C, On-site (field) testing of HRC in non-residential ventilation units (C1) or a HRC sections (C2) in operation configuration. This document is applicable to recuperators, regenerators, and HRC with intermediary heat transfer medium. This document prescribes test methods for determining: 1) the temperature and humidity efficiency, 2) the pressure drop of exhaust air and supply air sides, 3) possible internal leakages; exhaust air transfer ratio (EATR) and outdoor air correction factor (OACF), 4) external leakages and 5) auxiliary energy used for the operation of the HRC. HRC using heat pumps are not covered by this document.