A sample of a paper or board is conditioned and said to be in equilibrium with the conditioning atmosphere when it has been exposed to the atmosphere long enough for the results of two weighing of a test piece, performed at an interval of at least 1 hour. Temperature 10º to 60º C. Accuracy ± 0.5 ºC, Humidity range 30-90%. Accuracy ± 3%. Temperature below ambient is controlled by hermetically sealed compressor complete with accessories provided below the unit. Two stainless steel water reservoirs heated by immersion heaters are provided to create humidity. Complete with all accessories. Digital Control panel provided with control switches and indicators. Inner chamber size 700 X 450 X 450 mm.