Temperature Ratings
Because manufacturers have no standardized way of registering how warm a sleeping bag is, temperature ratings for sleeping bags remain an inexact science. Some manufacturers give a bag both a comfort rating and a survival rating known as a "season rating". These give some indication as to how manufacturers expect a sleeping bag to perform.

Construction
The principle of all sleeping bags is the same: to trap air and prevent its circulation so that the body heats the trapped air and keeps you warm while you sleep. This can be achieved in a number of ways.

Boxwall Used in cold-weather down bags, the filling is contained within box-like sections to minimize bunching.	Sewn-Through Filling is in separate oval channels, although heat is still lost through the stitching.	Offset Channels The filling is laid out in two layers to prevent bunching and heat loss through the stitching.	Shingle Slanted layers of overlapping fibers that fill with warm air to aid insulation.

Using your Sleeping Bag
Before using your sleeping bag, always check inside for spiders and other dangers, and shake it to make sure the filling is distributed evenly. During use, if the bag is too warm, simply unzip it too cool down, or use the bag as a quilt. If it's too cold, either put on some clothing, or use a silk liner or waterproof bivi bag to increase its performance. Always air your sleeping bag well after using it.

Sleeping Accessories
You'll need to get a sleeping mat as well as a sleeping bag to ensure a comfortable, dry night's sleep. Additional gear, such as bivy sacks, sleeping bag liners, and inflatable pillows, will also increase comfort.

Foam Mats The lightest and simplest type of mat, foam mats are best used on soft surfaces, such as sand or pine needles.	Air Mats They may be heavier and more expensive than foam mats, but air mats provide superior comfort and thermal insulation.	Sleeping Bag Liner Usually made of cotton or silk, sleeping bag liners trap air between your body and the sleeping bag.
A lightweight option, weighing as little as 1.1 lb (0,5 kg) Folds up quickly and easily for simple storage	Shorter mats may suffice in summer Exterior is covered in waterproof non-slip polyester material	Liners can be used on their own in hot climates Sleeping bag liners are easier to wash than sleeping bags
Bivysacks A simple waterproof bag that is used over a sleeping bag to keep it dry or used on its own as a shelter.	Inflatable Pillow An inflatable pillow adds some luxury to expeditions. Alternatively, fill a stuff sack with spare clothing.	Space Blanket A lightweight foil blanket for use in emergencies, space blankets can also be used as a temporary canopy.
in warmer climates, bivy sacks enable you to sleep outside without a tent	Outer layer of pillow is padded for extra comfort	Foil prevent body heat from escaping and deflects it back to the body