Those are the words SolaTec uses to introduce the AeroVest - an emergency vest made with metallized polyethylene and inflated with a straw, not unlike the popular Flexair pillow, a “one-time use pillow” sold into the hospital trade but rapidly gaining a cult following among ultralight backpackers.
Eighteen air pockets are connected through a common air supply, but separated by seams to prevent significant convection between pockets, and to give shape to the vest.
Warmth is provided by three mechanisms: the metallized inner surface of the fabric may prevent some radiative heat loss, the air between the shell and lining fabrics provides meaningful thermal resistance by entrapping dead air space, and because the vest is inflated with respired air, the initial temperature of the air inside the vest will likely provide a slight bit of temporary warmth.
Because the vest design is prone to heat loss out the neck and arm holes, the vest is probably most effective when layered over other clothing (such as a base layer), and under outerwear (ideally, a hooded shell jacket).
In spite of its apparent applicability for “one-time emergency use only”, keep in mind that the vest weighs only two ounces and, according to manufacturer claims, can be re-used.
For day hike in the winter, I could see the vest finding its way into my emergency overnight kit, especially if I brought little other insulating clothing, as I'm prone to do when I'm expecting a short backcountry hike of only a few hours where I'll keep moving.
For backcountry use, the vest would certainly serve its purpose as emergency kit, but I'm willing to bet that a few ultralight extremists would consider this an integral part of their clothing system. For example, I could see a backcountry hiker's clothing kit for a week-long May trek in the Utah desert composed of a knitted base layer (for hiking, and light warmth), a shell jacket (for rain and wind), and a two-ounce AeroVest for in-camp use, and to boost the temperature rating of a lightweight sleeping quilt on the 15% probability that the temperatures on one or two nights dips below forty degrees Fahrenheit.
Outside our Bountiful, Utah hotel this evening, I took the opportunity to see how much warmth the vest added to my ultra-thin clothing system: a Smartwool Microweight long-sleeve zip-T shirt and a Patagonia Ready Mix jacket.
First, I stood outside until I started shivering. That required all of about ten minutes in the 21 deg F air. Then, I stripped my jacket off, put the vest on, secured the vest around my body with its self-sealing tape strips, and added back my shell jacket. I waited until I started shivering again, then inflated the vest with its straw. (It's critical to inflate the vest once you have it integrated with your clothing system, or you risk overinflating it and not being able to layer over it with your other clothing.) The most difficult part of donning the vest was the inflation of it - aligning the straw into the inflation holes (there are two, near the top front of the vest) while wearing the vest is a trick, and requires a nimble neck.
I immediately felt warm, presumably due to the “warm” (98.6 deg F) air that I blew into the vest. However, I was able to stand around outside for quite some time, staying reasonably comfortable. It was quite obvious that the vest provided a substantial amount of heat loss resistance - at least compared to the shiver-inducing control condition without the vest in a hotel parking lot!
I laid down in the vest and didn't find it terribly uncomfortable - I'm pretty sure I could sleep in it without much duress, especially in an emergency situation.
Now, keep in mind. This is no down parka. It lacks the compressivity that provides down with its comfortable range of motion, nor does it provide that somewhat nebulous feeling of coziness. After all, it's a little crinkly and you do get the feeling that you're wrapped in a splint designed for broken ribs if you overinflate the vest. And, when it comes time to deflate it - good luck - it's no easy chore to get all the air out, so re-packability may be a problem. Admittedly, I didn't try to spend a lot of time perfecting air removal techniques.
I did sacrifice one, popping it with my fingernail. It required a surprising amount of force - certainly more than what's required to rip the typical ultralight mylar emergency blanket. With careful and periodic use, I think the vest could be reused for a few cold nights on a long hike, but don't expect it to provide the comfort - or durability - for daily, or thru-hiking use.
All in all, I like it, and the concept has potential. I could see an application where less “puffiness” might suffice. I'm certainly going to pack one for winter day hiking, and I just may give it a go on an overnight backpacking trek for a fairer evaluation, or at least some unique photo opportunities. Finally (don't try this at home), as long as it's protected under a durable shell, it just might appeal to packrafters looking for some swimming insurance for low-class floats.
Bottom Line: Cheap, lightweight, and effective insurance against hypothermia for winter day hiking and totally fringe occasional-use gear for the ultralight extremist. Weight: 2.0 oz, AeroVest.com, MSRP $14.95.