From Bushwalk Australia
When sleeping in tents (or even in huts) the ground (or floor) is rather unconfortable compared to what most of us are used to. But an even more significant problem is that the body's heat is absorbed into the ground very quickly meaning that not only is there a risk of feeling very cold during the night, but also a serious risk of developing hypothermia, which can be fatal.
Gone are the days when it was acceptable to cut enough fresh vegetation to build your own mattress at each campsite. There are now a variety of sleeping mats available commercially.
Sleeping mats serve two principal purposes: To insulate against the temperature of the ground (or floor), and to provide some level of comfort greater than that of the ground (or floor).
There are several different types of mats available, with some of them listed below. These are all available in various lengths, widths and thicknesses, and in some cases in different shapes. These variations result in different weight, packed size and comfort.
Closed Cell Foam
The popularity of these thin hard rubbery foam mats has waned with the growing popularity of more recent varieties that are better in terms of both comfort and packed size.
The remaining advantages of closed cell foam mats are that they are very cheap, and very durable (not subject to punctures in the middle of a walk).
Close cell mats are a lot less comfortable than other varieties, however, their protection from the cold is still very good.
Open Cell, Self-Inflating
Probably the most common bushwalking mats in use today, these foam mattresses are sealed into a vinyl covering with a valve to let air in/out during inflation/deflation. The springiness (or memory) of the foam causes these mats to self-inflate once the valve is open, and the mat laid out where it has enough room to do so (sometimes requiring a final breath/pump of air to fully inflate).
The mats are quite compact when deflated and rolled up, and therefore do not take up a lot of pack space. However, when not bushwalking, it is recommended to store them inflated/unrolled with the valve open to prevent the foam from becoming compressed permanently and losing the ability to self-inflate. This also allows moisture (from blowing into the mats) to gradually dry out while stored.
A mat of this type is often referred to as a 'Thermarest', after the company that made them well known.
One variation of this mat is that regular large holes in the foam are cut out before assembling. This reduces the weight of the mat even further, leaving just enough foam to partially self-inflate the mattress and provide a limited amount of insulation.
Inflated Tubes, Pump-Up
Similar to a traditional 'lilo' style airbed, but smaller and lighter, and using materials which improve insulation significantly. These mats require pumping up (or blowing up, if the manufacturer recommends it), and may be supplied with a tiny pump, which may also double as a pillow.
Because these mats rely entirely on inflation to achieve their main objectives, they are more vulnerable to puncture than other mat types. Some manufacturers have addressed this by using robust, puncture-resistant materials, but others may puncture easily.
It is a good idea to be particularly careful in protecting any inflatable mat from exposure to damage from sharp or abrasive objects, such as sticks and rocks, or sharp items in your pack. It is also essential to carry a small repair kit should a puncture occur during a walk.
Down Filled, Pump-Up
Similar to inflated tubes mats, down mats include down in the tubes. These mats require pumping up (a tiny pump is generally supplied with the mattress, which in some cases can double as a pillow). Blowing into these mats is not recommended as the moisture can reduce the effectiveness of the down.
These mats look a little like traditional air-beds, but smaller, with several tubes which need to be inflated.
Down filled mats are regarded as being more comfortable than other varieties, and have better insulation, but are also more expensive. They have the same problem as other inflatable mats in that they are easy to puncture.