Abstract: Laboratory equipment with flammable refrigerant and connected to at least two different electrical potentials for supplying the equipment with electrical energy. An electrical switch arrangement has first and second switches for electrical separation from, respectively, the first and second potentials. A sequence controller switches on the first switch and thereafter the second switch. A monitoring device is connected via a first contact on the equipment side to the first switch and via a second contact on the mains side to an electrical potential other than the first electrical potential for detecting a switched-on state of the first switch and signaling the detection to the sequence controller. When the monitoring device signals a switched-on state, the sequence controller blocks operation of the equipment as a function of the signaled switched-on state and whether the first switch is expected to be switched on or switched off.

Abstract: A method of operating an item of laboratory equipment cooled by means of a flammable refrigerant. The method includes ventilating an interior of the cooled laboratory equipment with the aid of a fan, wherein control of the fan is carried out over a first time period by a first control device; checking, with the aid of a first predefined criterion, whether the ventilation was successful; transferring control of the fan to a second control device if ventilation was successful over the first time period; checking, with the aid of a second predefined criterion, whether the fan is being successfully controlled by the second control device; activating a power supply for at least one further device, which is to be electrically powered, of the cooled laboratory equipment if the fan is being successfully controlled by the second control device. A corresponding item of laboratory equipment is also disclosed.