Police were called by the London Ambulance Service at 4.20pm to reports of a man aged in his 60s suffering from burn injuries caused by a chemical reaction at a block of flats in Battersea Park Road.
Officers, the LAS and the London Fire Brigade attended.
The man was arrested on suspicion of criminal damage with intent to endanger life.
He has been taken to a West London hospital.
We are awaiting an update on his condition.
As a precaution, nearby properties have been evacuated and road closures are in place while the area is made safe.
Nine Elms Lane is closed in both directions.
Officers remain on scene and enquiries continue.