Two pregnant women, two small children and a man were hospitalised after a carbon monoxide leak in a Dalston block of flats.
The five were found to have elevated readings of the deadly gas after a total of 21 residents forced to leave the four storey block in Kingsland Road were checked over by London Ambulance Service.
Firefighters wearing breathing apparatus swept the building where they discovered a gas leak.
The brigade now wants to encourage everyone to make sure they have a carbon monoxide detector in their home.
Shoreditch watch manager Mark Lanaway, who was at the scene, 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.”
The brigade was called at 10.57pm on Tuesday, September 29 with the incident over by 1.33am on Wednesday, September 30.