Although the EN13537 standard does not identify a single precise temperature a tested sleeping bag is suitable for, it does provide an industry standardised temperature range that a typical user can refer to as a guide for the conditions their bag will be most comfortable in.
The EN13537 standard provides three temperature levels to guide a consumer in their choice:

• Comfort: The temperature at which a standard woman can expect to sleep comfortably in a relaxed position. If you consider yourself a cold sleeper use this rating to decide the coldest temperature the sleeping bag is suitable for.
• Lower Limit: The temperature at which a standard man can sleep for eight hours in a curled position without waking. If you consider yourself a warm sleeper you can use this rating to decide the coldest temperature the sleeping bag is suitable for.
• Extreme: This is a survival only rating for a standard woman. Between the lower limit and the extreme rating a strong sensation of cold has to be expected and there is a risk of health damage due to hypothermia. This is an extreme survival rating only, we do not recommend you rely on this rating for general use.
  

The EN13537 temperature tests use a thermal manikin with heaters and temperature sensors to measure the insulation value of a sleeping bag. This manikin is wearing one layer of long underwear and is placed inside the sleeping bag on an insulating mat. The test is conducted in a temperature controlled chamber and a range of comfort temperatures are derived from measuring the energy required to maintain homeostasis in the manikin to a set temperature.

All Sea to Summit sleeping bags have been tested to the EN13537 standard. We recommend you use our EN13537 quoted ratings as a guide and a comparative reference to other EN13537 tested bags.