28 be avoided after exposure. If an individual suffering from the effects of a chemical irritant is restrained, his or her breathing shall be monitored constantly. Any unexpected or long-lasting effects should be referred for relevant specialist assessment and treatment. 7.2.5 The use of chemical irritants can temporarily cause breathing difficulties, nausea, vomiting, irritation of the respiratory tract, tear ducts and eyes, spasms, chest pains, dermatitis or allergies. In large doses, it can cause necrosis of the tissue in the respiratory tract and the digestive system, pulmonary oedema and internal bleeding.84 There is also the possibility of burns or other injury resulting directly from the solvents if they have not evaporated before contact with skin. There is a particular risk of flammability from the solvent, for instance if a subject is smoking. CIRCUMSTANCES OF POTENTIALLY UNLAWFUL USE 7.2.6 Irritants that contain carcinogenic substances or hazardous levels of active agents shall not be used. Repeated or prolonged exposure to chemical irritants should be avoided. Some solvents are toxic or flammable, or may cause corneal erosion.85 7.2.7 Chemical irritants should not be used in situations of purely passive resistance.86 In accordance with the principle of necessity, once a person is already under the control of a law enforcement official, no further use of a chemical irritant will be lawful. Chemical irritants should not be used in closed environments without adequate ventilation or where there is no viable exit, owing to the risk of death or serious injury from asphyxiation. European Court of Human Rights, Abdullah Yaşa and others v. Turkey, Judgment, 16  July 2013, para. 30. 85 See M. Holopainen et al., “Toxic carriers in pepper sprays may cause corneal erosion”, Toxicology and Applied Pharmacology, No. 186 (2003); and P. Rice, D. Jones and D. Stanton, A literature review of the solvents suitable for the police CS spray device (Chemical & Biological Defence Establishment, Salisbury, 1997). 86 US Court of Appeals (Ninth Circuit), Headwaters Forest Defense v. County of Humboldt, 240 F.3d 1185 (2000), pp. 1205–06. 84