It was the second similar incident in successive days in Limerick.
An army bomb disposal unit yesterday carried out a controlled explosion at St Enda’s Community college on the Kilmallock Road.
The previous day a similar incident occurred at Scoil Iosaf secondary school in Kilmallock.
The chemical which caused both scares, dinitrophenylhydrazine, is commonly used in laboratories at schools and universities.
Gina O’Connor, St Enda’s school principal, said: “In line with health and safety regulations and school policy we immediately contacted the emergency services.
“And following that we were advised to contact the services, and following that we were advised to evacuate the building, which we did. Parents were contacted and students, along with staff, were sent home. There was no risk to students.”