Forgive my ignorance, but are these supposed to replace the ubiquitous ‘orange bag’ that I have been carrying around since the year ‘dot’? (Walking, not biking)
They serve a similar role. They are designed to host a “group” (i.e. 2-10(?) people depending on the size of the bag. They are used sitting up, huddled close, which is a quite effective way to share heat, still be able to have a (moral boosting) conversation, keep the wind and rain off etc. It is amazing how quick they warm up. As placed over, rather than climbed into, an injured casualty can be accommodated without moving them. You can also managed to get a cold wet person changed into dry clothes in one, which is not too easy in the big bag.
Head first in a plastic bag obviously has a risk of suffocation and certainly would be clostrophobic. With the head not covered you’ll know that it is less effective.
You can probably accommodate 3 people in one the size of your folded orange bag (especially if your orange bag has ever been opened and refolded). The original commercial concept was developed by Karimor, and was known as the Karimor Instructor Survival Unit (KISU), and gives a very basic shelter.
Unlike a bag they are sort of breathable so you tend not to become wetter than when you went in!
No use for sledging.