A heat exchanger (1) contains: a bundle of at least two heat exchanger tubes (3), a heat exchanger housing (5) surrounding the bundle of heat exchanger tubes (3), wherein a liquid heat-transfer medium (7) is passed around the bundle of heat exchanger tubes (3) in the heat exchanger housing (5), a heat exchanger cap (9) sealing the top of the heat exchanger housing (5), a heat exchanger bottom (11) sealing the bottom of the heat exchanger housing (5), a feed point (13) for the heat-transfer medium (7), an outlet (15) for the heat-transfer medium (7), an emergency relief port (17) disposed in proximity to the heat exchanger cap (9). The heat exchanger (1) contains a safety device (19) disposed in proximity to the heat exchanger bottom (11).