A proactive fault detection and diagnosis (FDD) method is proposed for variable-air-volume (VAV) terminals in this study to overcome the problem of diagnostic information poor. The basic idea is to produce additional diagnostic information proactively through introducing specific disturbances to the suspected VAV terminal. The dynamic responses of the VAV terminal, which can be observed from the measurements and control signals, are helpful in isolating faults which are challenging for the conventional passive FDD methods. A list of proactive actions is designed to introduce the smallest disturbances into indoor environment. Therefore, the proposed method can work during office hours. Without loss of generality for practical applications, the proactive actions change the zone air temperature set-point only. The proposed method can be implemented in both building management systems and VAV terminal controllers. Evaluations are made on a simulated VAV system on Dymola platform. Results show that the method can improve FDD performance significantly. (C) 2018 Elsevier B.V. All rights reserved.