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