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.
Such mattresses weigh more than non-inflatable pads. Therm-a-Rest also sells a line of less-expensive, non-inflatable pads. Closed-cell non-inflatable pads can provide insulation from cold and hard surfaces more efficiently than open-cell inflatable pads, but with less comfort. Most backpackers consider the extra weight to be worth the increase in comfort. Therm-a-Rest also offer mummy bags, sleeping bags, and seating.
Similar mattresses are now available from competitors.
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