CALORIMETRY

Microcalorimetry apparatus includes a chamber in which a plurality of samples to be analyzed are supported. The chamber is surrounded by thermal insulation at least a portion of which is porous. Air at an accurately controlled temperature is supplied to the chamber under positive pressure to cause continuous exhausting of air through the porous insulation. A reference sensor is disposed in the chamber and provides a reference signal to accelerate equilibration of the samples in the chamber. The apparatus is particularly useful in detecting bacterial growth by sensing the heat production in the samples under analysis and sensing for a positive derivative of the rate of heat production in the samples.