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