We label all of our sleeping bags with a "comfort temperature" which is tested by an independent laboratory (AITEX) in accordance with European standard EN 13537 of 11/04/2002.
The "comfort temperature" is the lower temperature limit at which the user feels comfortable overall - neither hot nor cold - while lying in a relaxed position (temperature determined for an average woman under normal conditions of use).
CHOOSE YOUR SLEEPING BAG ACCORDINGLY
What are the temperature "limits" at which it can be used?
Comfort limit temperature: The minimum temperature at which a user feels comfortable overall - neither hot nor cold - while huddled up in the sleeping bag (as determined for an average male user under normal conditions).
However, here's what you need to know about temperatures:
A sleeping bag does not produce any heat. Rather, it retains the heat produced by the body. If you are tired and cold and you slip inside a cold, damp sleeping bag, you will most likely feel cold no matter how good your bag!
These temperatures depend on a person's ability to withstand cold (build, fatigue, etc.), his equipment (insulating mattress, etc.), the way he is dressed (if he is naked, wearing underwear, etc.), and weather conditions (damp, wind, etc.).
Tips for warming up before getting into your sleeping bag:
Don't overdress (1 layer of clothes is enough)
Keep your extremities warm: use hats, gloves, socks, bed warmers, rubbing, etc.
A flask filled with hot water can be used as a foot or bed warmer (so long as there's no chance of it opening by accident!)
Contract your muscles (70% of the energy your consume is transformed into heat) without making movements that could cause a draught
Tips for storage and maintenance
Machine wash - 30° max - normal
Do not bleach
Tumble dry - low heat
Do not iron
Do not dry-clean
Easily store your sleeping bag by stuffing it into its cover feet first. To keep it fluffed up, which will ensure good thermal performance, remove its cover and store it somewhere dry.