In Functions that have the return_header=TRUE option set the returned object is an AQSAPI_v2 object, this is a 2 item list where the first object is a tibble with the label $Header the second, a tibble with the label $Data. sampledata functions are limited by the API to one calendar year of data per API call so if the user requests multiple years of data the sampledata call will return multiple AQSAPI_v2 objects, one for each call to the API. The returned result is a list of AQSAPI_v2 objects. In R to access the data in each item in the list the user will need to use the “double bracket operator” (“[[", "]]”) not the single bracket operator (“[", "]”).