| A sleeping bag is a protective "bag" for a person | | | | synthetic fill cannot be compressed as much as |
| to sleep in, analogous to a bed and blanket. Its | | | | down, causing such bags to take up more space |
| primary purpose is to provide warmth and | | | | when not in use. |
| insulation. It also protects, to some extent, against | | | | Down fill weighs less than synthetic and retains |
| wind, precipitation, and exposure to view, but a | | | | heat better, but usually costs more. Down must |
| tent performs those functions better. The | | | | be kept dry; a soaked down sleeping bag may |
| bottom surface also provides some cushioning, | | | | provide even less insulation than no sleeping bag |
| but a sleeping pad is usually used for that purpose. | | | | at all, leading to hypothermia. Newer, more |
| A bivouac sack (bivy) is a waterproof cover for a | | | | technically advanced sleeping bags often have |
| sleeping bag that may be used in place of a tent | | | | water-resistant shells and can be used in damper |
| for lightweight travelers or as a backup if | | | | conditions. It is also recommended to keep a |
| inclement weather occurs. | | | | sleeping bag in a larger sack (storage sack) as |
| Design types | | | | opposed to the small traveling sack (compression |
| A basic sleeping bag is simply a square blanket, | | | | bag) during long periods of storage. |
| fitted with a zipper on two sides allowing it to be | | | | Other materials, notably cotton and wool, have |
| folded in half and secured in this position. A | | | | also been used for sleeping bags. Wool repels |
| sleeping bag of this type is packed by being | | | | water nicely and also resists compression, but it |
| folded in half or thirds, rolled up, and bound with | | | | weighs much more than any alternative. Cotton |
| straps or cords. The basic design works well for | | | | suffers from high water retention and significant |
| most camping needs but is inadequate under | | | | weight, but its low cost makes it an attractive |
| more demanding circumstances. The second | | | | option for uses like stationary camping where |
| major type of sleeping bag, sometimes called a | | | | these drawbacks are of little consequence. |
| mummy bag because of its shape, is different in | | | | Temperature ratings |
| a number of important ways. | | | | In Europe, the EN 13537 standard normalizes the |
| It tapers from the head end to the foot end, | | | | temperatures at which a sleeping bag can be |
| reducing its volume and surface area, and | | | | used. A test, relying on a heated mannequin, |
| improving its overall heat retention properties. | | | | provides four temperatures: |
| Some bags are designed specially to | | | | the upper limit is the highest temperature at |
| accommodate women's body shapes. | | | | which a 'standard' adult male is able to have a |
| It usually does not unzip all the way to the feet. | | | | comfortable night's sleep without excess sweating. |
| The zipper is a weak point in any sleeping bag's | | | | |
| insulating qualities. Together with the tapered | | | | the comfort rating is based on a 'standard' |
| shape, this design feature helps protect the feet, | | | | woman having a comfortable night's sleep. |
| which are more vulnerable to heat loss than other | | | | the lower limit is based on the lowest |
| parts of the body. | | | | temperature at which a 'standard' adult male is |
| It usually has a drawstring at the head end, to | | | | deemed to be able to have a comfortable night's |
| help prevent the escape of warm air. | | | | sleep. |
| A mummy bag often cannot be rolled like a | | | | the extreme rating is a survival only rating for a |
| rectangular bag. Instead, it is simply stuffed into a | | | | 'standard' adult woman. This is an extreme |
| stuff sack or compression sack. | | | | survival rating only and it is not advisable to rely |
| Fill | | | | on this rating for general use. |
| Many different insulating materials are available for | | | | The transition zone, in between the comfort and |
| sleeping bags. Avid outdoorsmen usually prefer | | | | lower temperatures, is usually considered as the |
| either synthetic fill or down, and they have | | | | best purchase guideline. |
| debated the merits of these materials for years. | | | | Slumber bags |
| Synthetic fill does not readily absorb water, dries | | | | The term slumber bag usually refers to a sleeping |
| easily, and provides some warmth even when | | | | bag for children, designed for indoor rather than |
| thoroughly soaked. These properties may save | | | | outdoor use. These are usually not designed to be |
| the owner's life if, for example, the sleeping bag is | | | | weatherproof, and often feature elaborate, |
| accidentally dropped into water on a cold day. | | | | brightly-colored printed designs, such as images of |
| Synthetic material is also firm and resilient, so it | | | | popular media characters. Slumber bags make |
| insulates well even underneath a person's weight. | | | | floor sleeping more comfortable, and are often |
| Synthetics also have the ability to loft faster than | | | | used for sleepovers, family visits, and other |
| down, allowing the sleeping bag to provide the | | | | situations where there aren't enough beds for |
| insulation faster than a down bag. On the flipside, | | | | everyone. |