How Therm-a-rest Pads Work

Engineers Jim Lea and Neil Anderson were looking to create a mattress pad lightweight enough for hikers to use but also comfortable for any outdoorsman to use. Trying various ideas such as using an old sandwich maker, memory foam and polyurethane sheets, in 1972 they eventually came up with Therm-a-Rest pads, the first ever self-inflating mattress pads. How Therm-a-Rest pads work may seem to be a mystery, but in reality it's just simple engineering.

Outer Material

Therm-a-Rest pads are made using twi polyurethane sheets as the outer coating. The reason the pads are made of this type of material is due to the fact it isn't porous, so air won't leak in. The two sheets are completely sealed off, except for an air valve. Air control is essential for the pad to function properly.

Foam Inside

Inside the two polyurethane sheets is a material called polyurethane foam, which is the same size as the outer sheets. Polyurethane foam is an open-celled material, meaning that if you put pressure on it, it will retain its original form once the pressure is off. It condenses down to a much smaller size when all air is forced out, but once the foam is exposed to air, it will regain its original form and size.

Inflating

Air is the basis for how the mattress inflates on its own. When deflated, there is no air in the mattress, so by opening the valve you allow air to flow into the inner chamber of the mattress -- where the polyurethane foam is. Once the foam is exposed to air, it expands to the same size as the outer sheets of the mattress, providing a fully-shaped and full mattress pad.

Deflating

When you want to continue your camping or hiking adventure, you will need to deflate your Therm-a-Rest pad.To do so, you must force all air out of the mattress by opening the air valve and rolling up the mattress. This will ensure you're removing all air and condensing the pad to its smallest possible form. Once all the air is out, close the valve so air won't get back in, causing the mattress to re-inflate.

Uses

Therm-a-Rest pads are an option for anyone who wants to get a comfortable night's sleep outdoors. They can be ideal for hikers who can't carry large, heavy equipment or machines to blow mattresses up, or those seeking an easy solution to resting comfortably without taking the time to manually blow up a mattress pad.