Firefighters were called to a suspected chemical incident at a flat on Woodman Road in Chigwell.
Crews investigated a strong smell of chemicals in the property and used detection, identification and monitoring equipment to sweep the building, but no elevated readings of chemical substances were found. A 25-metre cordon was put in place as a precaution. One woman was treated on scene by London Ambulance Service crews.
The Brigade was called at 1750 and the incident was over for firefighters by 2143. Two fire engines from Woodford and Romford fire stations and three fire rescue units from Bethnal Green and Euston fire stations attended the scene.