This rule extends the laboratory and analytical use exemption for the production and import of class I ozone-depleting substances through December 31, 2021. The Environmental Protection Agency (EPA) is taking this action under the Clean Air Act, consistent with a recent decision of the Parties to the Montreal Protocol on Substances that Deplete the Ozone Layer. The exemption allows the production and import of controlled substances in the United States for laboratory and analytical uses that have not been already identified by EPA as nonessential.