Companies frequently asked us how often they should be testing their crude oil. Deerfoot recommends a best practice of sampling your crude oil at least annually. A new well, formation, or process change can trigger the need for resampling. A production change, well stimulation in the depth of drilling can also trigger the need for sampling. The samples need to be sent to an accredited lab, with experience in the oil and gas industry. TDG regulations are separate from WHMIS classifications and changes in the composition of the crude oil may require updating the TDG classification. Aside from seasonal variations to composition and blending most crude products are retested for TDG purposes on an annual basis; significant changes may warrant SDS reauthoring. A TDG proof of classification document is recommended to provide the result according to the last sample date.