This has to be one of those great hiking myths like whether you need to filter/purify your drinking water. (in most cases, No, but if you want to, consider this post: Trouble With Water Filters).
Folks are convinced that the moisture (nasties?) in their breath will ruin the inside of their hiking mat so they carry an assortment of inflation bags or other devices for blowing them up.
By and large this is just unnecessary weight, like so many other things. See A Lazy Man’s Guide to Hiking and Hunting for some facts and figures on this point.
‘Why Is This So?’ – as Prof Sumner-Miller used to say, so long ago.
Should You Carry an Air Pump? What is the humidity of human breath compared to air? Perhaps 20%-90% for human breath – about what I had guessed.
Indeed (that is) not significantly different from ambient air such that using an air pump to blow up an inflatable mattress doesn’t actually make any sense. Certainly carrying the weight of it does not.
Correct drying procedure of the mat (after use) makes more sense. Dry it in a warm room eg hanging up with the valve open, as you do your sleeping bag – or should.
You can google the question yourself. Here are a couple of answers I came up with: https://www.researchgate.net/publication/337064921_Measurement_of_temperature_and_relative_humidity_in_exhaled_breath & https://www.sciencedirect.com/science/article/abs/pii/S0925400519315709
Just another of the myths of the hiking community – like ‘leave no trace’, dry feet, water filtration and canister stoves.
For comparison, one of the lightest pumps (The Flextail) weighs around 100 grams – ditto inflation sacks etc.
I recently had to cut up one of my much-loved mats (Exped Synmat HL Winter M) because it had developed a ‘pregnancy’ problem, like this:
Probably because I am too heavy for it, or too hard on it. The wonderful folks at Exped (and Tom’s Outdoors where I bought it years’ ago) nonetheless have an excellent warranty scheme, so that it was replaced quickly and at no cost.
It has been out in the bush with me lots and lots of times, as well as on the EBC and the Dusky Track & etc.
Here are some shots of what it looks like inside. You can see how it was made quite clearly:
You can even see one of my Cuben Tape repairs.
But the really important thing to note is how white and clean the inside really is after having been used, inflated (by breath) and deflated hundreds of times. No mould or other discolouration. Like new.
There was absolutely nothing different between the humidity (or other qualities) of my breath as compared to the ambient air, so that there really was absolutely no reason to inflate it in any other way. I rest my case.
Others apart from me have been exploding this myth (eh=g by weighing the pads before/after & etc. See eg: https://backpackinglight.com/forums/topic/does-inflating-a-sleeping-pad-with-your-breath-really-lower-its-r-value/
See Also:
A Lazy Man’s Guide to Hiking and Hunting
Thankyou – this is really interesting and priceless to see actual visuals of the internal construction (not just drawings), and extremely interesting to see first hand evidence of the state of the inside of a heavily used but properly cared for mat. Which still looks pretty good!
There are some US youtube hikers who have shown pictures of their mats held up to the sun to show the mould that has developed inside when inflating by lung. But ! What they fail to say, and given you can see how they are using their mats (weeks or even months with them rolled tight after deflating inside the pack while walking on a major PCT, CDT etc hike), I doubt that they get any chance to leave them hung out to air (and dry out).
You have suggested a really valuable point about the need for hanging and airing of gear.
Thanks Craig. The mould would grow in the presence of water whatever you blew them up with if you made no attempt to dry them out. You should leave the cap off when they are not inflated so that air and water vapour can escape. You can keep them rolled up with a small length of webbing with a buckle on it (on the trail) – which is what I do. I am going to use the ruined mat to make pillows with soon. Stay around to watch. Cheers, Steve.