Something to keep in mind is that an in case humidifier is somewhat static. Yes, certainly better than nothing, but I believe a bigger problem is the environment where the concertina gets played. If you think about it, when you play your concertina in a room or house that is 30% humidity or less what you are in effect doing is "kiln drying" the instrument from the inside out as you pump all that dry air through it.
I try and encourage my customers to use a small room humidifier in a dedicated playing room or area. A minimum 50% humidity is the goal. (70% or better seems to be a tipping point where unwanted things start growing... )
Concertinas apparently can gradually adapt to dryer environments and I've worked on concertinas from Arizona, California and the high plateau of Colorado which have seemed to be healthy and intact. So perhaps the most dangerous situation may be a relatively sudden "shock" to the wood of an instrument when a seasonal change occurs or a prolonged cold spell happens and central heating runs continuously and relative humidity drops drastically.
Corner support blocks which keep the reed pan in place are very vulnerable. As the bellows pan wood dries and changes shape the brittle hide glue which holds the support blocks can give way. The result is bleeding notes or loss of volume usually in a corner area of the concertina shared by the affected notes. Worst case scenario is that the pad board shrinks and suffers a crack between or through several pad holes. (Mahogany pad boards seem more prone than maple/sycamore although I've rarely seen an Edeophone with pad board cracks. 12-sided shape alleviating stress??)
So I'd advise not only using an in case humidifier but paying attention to your home playing environment. Around my house October is when I start the humidification of the project room and workshop so that I stay in front of the winter heating drying curve.
As an illustrative aside I still remember playing a little banjo with a skin head on the University of Florida campus commons one winter's day. Too much humidity is often the problem in Florida and I was always tightening the rim brackets to keep the skin head of the banjo from sagging. On this rare day a Canadian system had rushed in bringing exceptionally clear, blue skies along with a sudden drop in humidity. I was enjoying the rare dry weather and no doubt trying to impress some coeds with my banjo prowess when a distressing "rrriiipping" noise came from my lap. I quickly determined the sound was not from a failure of pants bottom integrity but sadly the tearing of my banjo head. The sudden drop in humidity had self tightened my banjo head beyond its breaking point!
My winter mantra: Humidify. Humidify. Humidify.
Edited by Greg Jowaisas, 30 March 2017 - 09:20 AM.