Two fire engines from Haverhill and one from Bury St Edmunds were called to a report of an incident involving chemicals at Vion Food in Little Wratting just before 2pm today.
Two cleaning agents - sodium hypochloride and phosphoric acid foam - were reported to have mixed together and caused a reaction.
The chemicals were quickly contained and the Fire Service left the site just before 4pm.
A specialist firm has been contacted to clean up.
One worker was taken to Addenbrooke’s Hospital, Cambridge, suffering from breathing difficulties.