Gases can be formed in oil-filled electrical equipment due to natural ageing of oil and, more frequently, as a consequence of faults. In the event of a more severe fault the free gas in the oil rises and is collected in the Buchholz relay.

With the Buchholz gas sampler BGS, these gases can be sampled easily and analyzed directly on site by using the Buchholz gas testers BGT 4.1 & BGT 4.2.