Firefighters spent nearly three hours battling a blaze at a car repair workshop in Edgware on Tuesday (17).
Six fire engines were called to Edgware Crash Repairs, in Ballards Mews, High Street, at 5.15pm after several calls from people in the area.
Workers were evacuated from the building after a large oven used to dry paint on cars caught alight.
Firefighters with breathing apparatus entered the building to remove a cylinder, however two aerosol cans exploded at the scene.
Chris Whelpton, a watch manager at Stanmore Fire Station, said: "When we arrived there was smoke all up the road and people waving at us.
"We had to get through quite a lot of traffic to get here, but we responded quickly and there were five or six businesses nearby and we prevented the fire from spreading any further."
Fire investigation teams confirmed the blaze was caused by a fault within the oven. The single-storey shop remains closed after the incident.