Bticino HC4511/12 Notice De Montage page 58

WARNING! 57
If there is an alarm or if gas is detected:
1) Extinguish all free flames
2) Turn the gas meter tap off
3) Do not turn lights on or off; do not use electrically powered
equipment or devices
4) Open doors and windows to increase ventilation.
If the alarm stops, you must identify what caused it to turn on
and act accordingly.
If the alarm does not stop and you cannot detect or eliminate
the presence of gas, leave the premises and, once outside, call
the emergency service.