It consists of salt hydrates which, unlike paraffins, are not combustible. This makes DELTA®-COOL ideal for use even in buildings where fire-prevention requirements are stricter than normal. Under the influence of heat, DELTA®-COOL changes its state of aggregation from solid to liquid as it reaches its melting temperature. The heat thus stored is emitted again as soon as the phase change is reversed. In this way, temperature fluctuations may be mitigated and temperatures peaks prevented without any need to expend energy on cooling.