http://hl7.org/fhir/StructureDefinition/openEHR-exposureDuration|4.0.1

The amount of time the individual was exposed to the Substance.
typedestination
baseDefinitionhttp://hl7.org/fhir/StructureDefinition/Extension
typehttp://hl7.org/fhir/StructureDefinition/Extension
Extension.value[x].typehttp://hl7.org/fhir/StructureDefinition/Duration