ISO 45001 defines the terms “Occupational health and safety OH&S opportunity” as “circumstance or set of circumstances that can lead to improvement of OH&S performance”.
Opportunities are inverse impact of risk where there is ample opportunity for the organization to improve instead of a negative impact, it is a positive vibe for the organization.
Opportunity can be rated in subjective basis and can be converted on corresponding numerics if the criteria is developed in an organization.
See the document for opportunity you have to maintain for ISO 45001 implementation.
The purpose of considering OH&S opportunity in the OH&S management system is the fact that organization should take into account positive prospects in order to maximize them in favor of the organization.