The Meaning of Self-Inflating Sleeping Pads
We get a lot of questions about our self-inflating sleeping pads. How do they work? Do I have to blow them up at all? How should I store a self-inflating sleeping pad?
All great questions, so we've answered them here:
Photo by Lisa Paarvio
1. How it works.
A Therm-a-Rest self-inflating mattress is indeed a layer of open cell foam, enclosed in a sandwich of airtight fabric. The natural tendency for foams to rebound when compressed is what draws air into the mattress for “self-inflation”. Forty-two years ago, Jim Lea, John Burroughs and Neil Anderson mocked this concept up on a wooden press the size of a large book and it worked. The rest is history.
Photo by Lisa Paarvio
2. Getting the Most of It.
We choose our internal foams for, among other things, their light weight and "memory", meaning their tendency to bounce back after being compressed. When you first buy a mattress, it has likely been rolled for some time. To recalibrate the foam in a new mattress, lay it out and open the valve for at least 24 hours prior to your first use, letting it re-expand to its natural resting state. Then, somewhat paradoxically, it will “remember” being fully lofted the next time you roll it for a trip and you’ll get maximum self-inflation when you un-roll it.
Photo by Bard Basberg
3. The “Myth-understanding”
Sorry, but a Therm-a-Rest self-inflating mattress really does need your help sometimes, but just a little. Though it depends greatly on the mattress (based on the type and thickness of the foam we use), once you open the valve, your mattress will begin to inflate - by itself. That’s the “self” part. However, to be completely transparent, you may indeed need to top off your mattress with a few breaths of air to achieve your desired firmness. For a softer sleep on a thicker mattress, you might not, but most people will puff a breath or two to firm things up.
Photo by James Barkman