Therm-a-Rest
Therm-a-Rest is a trademarked name for a line of self-inflating camping mattresses. They were invented in the early 1970s by two former Boeing engineers and avid backpackers. They named their company Cascade Designs.
A Therm-a-Rest air mattress consists of an airtight nylon fabric envelope filled with a sheet of low density, open-cell polyurethane foam. When a valve is opened the foam expands and draws air into the mattress. When the mattress has fully inflated the user simply closes the valve. To increase firmness a few breaths of air can be blown into the mattress. To pack the mattress the valve is opened and it is rolled up tightly to force the air out, whereupon the valve is closed to prevent re-inflation.
Compared to traditional, closed-cell non-inflatable pads, open-cell inflatable pads weigh more, and provide less efficient insulation from cold surfaces; many backpackers, however, consider the extra weight to be worth the increase in comfort.
Therm-a-Rest also sells a line of less-expensive, non-inflatable pads, as well as mummy bags, sleeping bags, and seating.
Similar self-inflating mattresses are now available from competitors.
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