As of 1 January 2005 a CEN criterion came into effect covering the testing and publication of temperature ratings for sleeping bags.
This criterion has significant legal connotations for brands, distributors and retailers selling sleeping bags in Europe.
The criterion was originally published in 2002 and has now been adopted in most European countries, and also used by numerous outdoor companies outside of Europe.
The criterion is used in the following countries: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, the Netherlands, New Zealand, Norway, Poland, Portugal, Romania, Slovakia, Spain, Sweden, Switzerland, and United Kingdom.
These ratings are taken assuming that the subject is using a sleeping pad with an R-value of approximately 5.38, tent and is wearing one base layer of thermal underwear, socks and warm hat.