Egyptian Minister of Health Amr Hilmi said that the expired tear gas used against protesters in Tahrir Square is less dangerous and less effective than unexpired tear gas. Hilmi said that the gas is like expired medicine that does not harm the patient but does not heal him. He also said it is not proven that expired tear gas or nerve agents were used during clashes in Tahrir Square. Tear gas canisters were sent to the chemistry department to be analyzed.