Provided is a trace gas measurement apparatus for electrical equipment that includes at least one sample cell configured to collect an oil sample from the electrical equipment. The sample cell having an oil receiving portion for receiving an oil sample, at least one perforated or porous sheet within a head space thereof for receiving the oil sample from the oil receiving portion, housing the oil sample thereon, and separating a new oil sample received from an existing oil sample within the at least one sample cell. The trace gas measurement apparatus also includes an oil pump for selectively pumping oil into and out of the sample cell, and a control module controlling operation of the oil pump, to adjust an oil level and air pressure within the sample cell, for performing an extraction process of trace gases within the oil sample.