How Do Self-Inflating Mattresses Work?

Self-inflating mattresses, also known as SIMs, work by using were first invented by Thermarest and have since become a popular choice for campers. They offer a lightweight, comfortable, and durable alternative to air beds, which can be bulky and prone to leaks.

With a variety of sizes, materials, and designs available, self-inflating mats cater to different needs, from compact backpacking mats to luxurious king-sized options. But how do they work? This guide explains the technology behind SIMs, the different fabric types, valve systems, and what to consider when choosing one.

How Do Self-Inflating Mattresses Work?

Every self-inflating mattress is designed with a foam core enclosed in a sealed fabric shell, combined with a valve system that allows air to enter and exit. When you open the valve, the foam expands and pulls in air, inflating the mat without the need for a pump.

The level of inflation depends on the thickness and density of the foam, which typically ranges from 3cm to 16cm. Thicker mats provide greater comfort and insulation, while thinner mats are lighter and easier to pack.

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Material Types: Nylon, Polyester & Polyester Pongee

The outer fabric of a self-inflating mattress affects durability, weight, and comfort. Below are the main fabric types:

Nylon

✔ Found in lightweight, high-end models.
✔ Extremely durable and long-lasting.
✔ Ideal for backpackers and frequent campers.

Polyester

✔ The most common material in self-inflating mats.
✔ Offers a balance of durability and affordability.
✔ Typically features a 75D (Denier) fabric for reliability.

Polyester Pongee

✔ Used in premium models from brands like Vango and Outwell (e.g., Shangri-La and Dreamboat collections).
✔ Brushed surface for a soft, bed-like feel.
✔ Popular among family campers looking for extra comfort.

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The Valve System: Inflation & Deflation Made Easy

One of the most important aspects of a self-inflating mattress is the valve system, which controls inflation and deflation. Modern valves have improved efficiency, making setup and packing away easier.

Brass Valve (Traditional)

• The original self-inflating mattress valve.

• Difficult to fully deflate as air can re-enter when rolling up.

AFC Valve (Air Flow Control)

• Modern valve design that allows for faster inflation and deflation.

• Found in Vango and Outwell SIMs, making setup quick and effortless.

Cyclone Valve

• Works similarly to the AFC valve.

• Features separate inflate and deflate settings to speed up packing away.

Foam Core: The Heart of Every Self-Inflating Mattress

Inside every SIM is a foam mid-core, which expands to draw in air. Some mats feature die-cut foam, where small sections of foam are removed to create air channels. This reduces weight and allows faster inflation, but removing too much foam can decrease insulation.

For cold-weather camping, check the R-value of the mat. A higher R-value provides better insulation, preventing heat loss from the ground.

Choosing the Right Self-Inflating Mattress

When selecting a SIM, consider:
✅ Thickness – Thicker mats provide more comfort but take up more space.
✅ Fabric Type – Nylon for durability, Polyester for affordability, Pongee for luxury.
✅ Valve System – AFC or Cyclone valves make inflation/deflation easier.
✅ Pack Size & Weight – Essential for backpacking or space-conscious campers.
✅ R-Value – The higher the R-value, the better the insulation in colder conditions.

Popular Self-Inflating Mattresses at WM Camping

🔹 Vango Shangri-La 15cm Double – A thick, luxurious option for family camping.
🔹 Outwell Sleepin 10cm Sinlge Mat – Premium comfort with a soft-touch finish.
🔹 Vango Trek 3 Trek Pro Mat – Lightweight and compact for backpacking.

Wrapping Up

Self-inflating mattresses provide the best balance of comfort, insulation, and convenience for campers. Whether you're looking for an ultralight mat for trekking or a luxurious option for family camping, there’s a SIM to suit your needs.

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Would you like recommendations based on your camping style? Contact us for expert advice!