A mass comparator including a weighing chamber (16); a draft shield (18, 20, 22), which surrounds the weighing chamber; a climate module (34), which is detachably disposed in the weighing chamber; a processor (32), a data input unit, and a data transmission path, over which data is exchanged between the climate module and the processor. The processor is programmed to use the air pressure, the air humidity and the air temperature in the weighing chamber to determine, based on the density of a substance to be weighed, an air buoyancy of at least one test sample and/or a buoyancy correction factor. Also disclosed are a climate module configured to electrically yet detachably couple to a mass comparator, and a method for operating a mass comparator including determining the air buoyancy and/or the buoyancy correction factor.

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