first issued 1992; most recent is 7th edition 2008.
This standard is produced under the auspices of the International Institute for Building-Biology and Ecology. This originated in Germany but is now based in the USA as a not-for-profit educational organisation.
They are based on the building biology experience and knowledge and focus on achievability. In addition, scientific studies and other recommendations are also consulted.
They are sometimes referred to as the "Salzburg" levels but we have not been able to find what the official basis for this is.