A chemical reaction at Steris Corporation in Millcreek forced the evacuation of the plant this afternoon. The incident created an emergency situation. Authorities advised anyone living or working within a half mile of the plant to close their doors and windows. The Erie County Haz-Mat team responded to the scene. West 23rd St. from Pittsburgh AVe. to Peninsula Drive was closed. The chemical reaction occured within a 700 gallon storage tank inside the plants production area. One worker was taken to the hospital for treatment.