ISO 20121:2012  specifies requirements for an event sustainability management system for any type of event or event-related activity, and provides guidance on conforming to those requirements.

ISO 20121:2012 is applicable to any organization that wishes to:

establish, implement, maintain and improve an event sustainability management system;
ensure that it is in conformity with its stated sustainable development policy;
demonstrate voluntary conformity with ISO 20121:2012 by
first party (self-determination and self-declaration),
second party (confirmation of conformance by parties having an interest in the organization, such as clients, or by other persons on their behalf), 
an independent third party (e.g. a certification body).
ISO 20121:2012 has been designed to address the management of improved sustainability throughout the entire event management cycle.