Neutralisation is the term used for counteracting an acid against an alkali (or vice versa) to bring its pH value to pH7 (the centre of the pH scale). The term neutralise implies removing the risk from a chemical. For example, bleach may neutralise the risk from a biohazard, or water may neutralise the risk from an exothermic material.
To neutralise the risk posed by a material it is necessary to know what the initial hazard is and what decontamination additive could be used to counteract its effect. A fire and rescue service may encounter many common materials where an additive will neutralise the effect. In all cases, initial responders will need advice from a hazardous materials adviser (HMA) or scientific adviser.
Some additives may present risks of their own and may only be suitable for use on chemical protective clothing (CPC) and not on the skin. Therefore, the use of an additive will vary depending on who or what is being decontaminated