A compression sack is a special type of stuff sack with straps which tighten a cloth lid over the bag, compressing the contents. A dry bag is a waterproof bag, often used in watersports, that seals shut to keep the contents dry. A dry compression sack is simply a combination of these two features into one sack.
Whether you’re camping, hiking, rafting, or preparing a bug out bag for emergency use, it’s a good idea to keep your clothes in a dry compression sack to save space and ensure you’ll have dry clothes at all times.
The Airpurge Dry Compression Sack by Outdoor Research is the one I use in my bug out bag. I bought the 30 Liter version, but as you can see in the following video, that is far larger than I need for my clothes — the 15 Liter bag would probably have been large enough. It also comes in 10 and 25 Liters.
In this video we tested the Airpurge by filling it with some clothes and floating the bag in a tub for ten minutes to see if it would keep everything inside dry. I also submerged it for a couple of minutes. Air bubbles floated up from the airpurge strip, but no water leaked into the bag — everything stayed nice and dry.
Not Everything Should be Compressed
Compressing your clothes will reduce their volume, and the space savings will allow you to pack more stuff in a smaller bag. However, some items are not suitable for long term compression. For example, I have a Marmot down jacket and a Marmot Hydrogen sleeping bag. These are fine to compress for a day’s hike, but if they remain compressed too long they lose their loft, and therefore their insulating ability. Accordingly, I don’t store these items compressed.
In sum, the Airpurge Compression Sack worked — even when fully submerged for about two minutes, and after floating in a tub of water for ten minutes, it kept the contents dry. It would certainly protect the contents if you got caught in the rain or if you spilled your kayak into the river.