Hazmat crews were called to a downtown laboratory where a chemical spill took place just after midnight.
It happened on the 11th floor of a building located at Bay and Gerrard streets where an employee was exposed and poisoned.
The man called 911 after the lab experiment went wrong and was taken to hospital where he is now listed in serious condition.
According to police, the area has deemed safe and there is no risk to the public.
The Ministry of Labour has been called in to investigate.