The HPD Open Standard is updated periodically. HPD v1 was introduced in 2012, and the current version, HPD v2.1.1, became effective in December 2018. On May 7, 2019, Version 2.2 was released, and is planned to be fully implemented in Q3 2019. Until Version 2.2 is fully implemented, the "current" version of the Standard remains v2.1.1.
There is no need to choose a version of the HPD to create and publish your HPD. HPDC provides an online tool, HPD Builder, that is always kept up-to-date with these requirements.
If you are an architect, designer or a user of an already published HPD, you can find the version designation on the cover page of the HPD report. The HPDC website provides information on all versions of the Standard at this link, should you need reference information.
Manufacturers may choose to update previously published HPDs. When that happens, the new HPD will be published under the current HPD version. The old HPD may at the same time remain valid as long as it is within the expiry date printed on it.