86 Resource book on the use of force and firearms in law enforcement With respect to the use of horses, the Manual emphasized that, while the use of horses offers unparalleled advantages in monitoring and controlling crowds, a rider does not have full control of the whole body of a horse and is not at all times able to instantly correct the level of force used. It is essential to use horses in the right situations and to make an assessment of how crowds may react. For example, for security reasons, horses should not be used in close proximity to barriers, and when used for the dispersal of crowds, escape routes should be identified and communicated. a OHCHR, Human Rights and Law Enforcement, A Manual on Human Rights Training for Law Enforcement Officials, 2017, chapter 9 (Human Rights and Policing of Public Assemblies and Protests), pp. 220-221. Chemical irritants: pepper spray and tear-gas Description and use There is a wide variety of chemical irritants used in law enforcement, usually for riot control purposes, known as riot control agents or RCAs.183 Different types of chemicals have different effects and therefore their use bears different legal implications. RCAs affect the peripheral senses. Yet, there are other chemical toxicants (e.g. fentanyl derivatives) that affect the nervous system as a form of anaesthetic, which should never be used in ordinary law enforcement due to the risk of death and permanent disability to those exposed.184 The most widely known RCAs are colloquially known as pepper spray and tear gas.185 What are their effects? All RCAs cause intense irritation and pain in the eyes, respiratory tract and skin, which results in crying, coughing, chest tightness, and difficulty breathing. These effects are often accompanied by anxiety and panic. More severe effects such as vomiting and skin blistering can also occur, as well as permanent damage to the eyes, skin and lungs, depending on the degree of exposure. The toxicity of different RCAs varies, and the severity of injuries caused will depend on a combination of factors including the specific chemical agent, its concentration, the exposure duration, the delivery method (liquid, smoke, aerosol, powder), the environment (indoor/outdoor and weather conditions), and the vulnerabilities of the victim (age, health). The concentrations of the active chemical can vary greatly among different weapons and there are no international standards regulating the weapons marketed by manufacturers. Solvents mixed with riot control agents can also be toxic. Exposure to high concentrations of such chemicals, or over a prolonged period, can cause severe injury or even death. Therefore, the use of RCAs must be carefully controlled, and they should not be used in confined or enclosed spaces. Even low concentrations can cause serious injuries to vulnerable groups such as children, the elderly or those with sensitivities or medical conditions, such as asthma. 183  See Chemical Weapons Convention (CWC), article 2: “Riot Control Agent” is defined as “any chemical not listed in a Schedule, which can produce rapidly sensory irritation or disabling physical effects in humans which disappear within a short time following termination of exposure.” 184  See ICRC position on the use of toxic chemicals as weapons for law enforcement, available at: https://www.icrc.org/eng/resources/documents/legal-fact-sheet/2013-02-06-toxic-chemicals-weapons-law-enforcement.htm 185  The most common chemicals used in law enforcement include o-Chlorobenzylidene Malononitrile (CS), Chloroacetophenone (CN), and Dibenz(b,f)-1,4-oxazepine (CR), which are often referred to as “tear gases”, and oleoresin capsicum (OC) and pelargonic acid vanillylamide (PAVA), often referred to as “pepper sprays”.