Firefighters wearing breathing apparatus had to ventilate an office building in Notting Hill after a carbon monoxide leak was detected.
They were called to the address in Acklam Road at 9.10pm on April 11 after being contacted by Southern Gas Network, which received elevated readings of carbon monoxide from the five storey office building.
The scare comes after seven people were taken to hospital with carbon monoxide poisoning earlier in the year.
Three people left the building before the arrival of the fire crew and were unharmed. Firefighters from Hammersmith then swept the building and ventilated the premises.
The incident, which was dealt with by 11.20pm, prompted London Fire Brigade to appeal to make sure everyone has a carbon monoxide detector in their home.
A spokesperson said: " Carbon monoxide is a silent killer , with least 50 deaths nationally recorded every year as a result of carbon monoxide poisoning.
"Despite this, the majority of people still do not have a carbon monoxide detector in their home. It is vital that everyone has a carbon monoxide alarm in addition to smoke alarms.”
They should be placed in rooms with fuel burning appliances, such as boilers in kitchens and fires in the lounge.
The spokesperson also offered the following advice:
Ensure your home has enough ventilation and airbricks are not blocked
Keep chimney flues free from blockages
Never use a purpose-built or disposable barbecue indoors
Get a Gas Safe registered engineer to inspect your gas appliances
Two fire engines and 10 firefighters attended the scene.
The incident happened just hours after a block of flats in Wembley was evacuated after a gas 'explosion' turned out to be a leak that left some residents requiring treatment .