Police said the leaked chemical is believed to be hydrochloric acid and that the building, on the site of Chemtura Manufacturing, had been evacuated.
The cause of the leak was not yet known.
Superintendent Chris Ullah from Greater Manchester Police said:
Emergency services are working at the scene to control the leak and motorists are being asked to avoid the area. We will keep the public updated but would ask people around the Trafford Park area to stay indoors for the time being as a precautionary measure.
More top news
Hazardous Whirlpool tumble dryers has led to at least 750 fires since 2004, a House of Commons report said.
The fast mover in lane eight enjoyed the freedom of one of the world's most famous landmarks and refused to be slowed down by the law.
Inflation has dropped from a near six-year high, as falling clothes and toy prices helped ease pressure on household finances in December.