This is the ValueSet that contains all the codes in Acute Care Hospital Encounter Class ValueSet (http://hl7.org/fhir/us/nhsn-dqm/ValueSet/ach-encounter-class) and Acute Care Hospital Encounter Class ValueSet (http://hl7.org/fhir/us/nhsn-dqm/ValueSet/ach-encounter-class). E.g. what you have to deal with if you get resources containing codes in either of them