Gas collecting devices for Buchholz relays can be used for a specific analysis to provide information on the status of the transformer or on-load tap-changer. When installed at a user-friendly working height, the fault gases can be safely and reliably sampled from the Buchholz relay. It is possible to draw reliable and meaningful conclusions regarding sources of error in the transformer or on-load tap-changer from the analysis results (e.g. with MESSKO® Gas Quick Test).