On Wednesday 8 October 2025, the white smoke came out from the heating plants at Meyrin and Prévessin sites, meaning that the heating has been turned back on. The heating and feeling of warmth will spread throughout CERN and all buildings will be heated within the next few days. 

The date on which the heating is switched on is determined to optimise energy consumption. Delaying its turning on was one of the measures of the Energy Savings campaign launched in 2022 and included in the measures foreseen by the ISO 50001 certification.

According to these measures, the heating switch-on is no longer defined on the basis of a regular calendar but on the weather forecast, and more specifically on the average overnight temperature. Each day saved through postponing the heating start represents significant energy savings for the Organization.

We therefore thank everyone for their understanding and supportive efforts.