I tried, I thought I could make it work, it seemed so easy, but alas, in my project to turn a used $3 cigar box into a functional humidor I failed miserably. I never could make the box airtight enough AND allow enough air to circulate through to keep the cigars moist enough with a passive humidifier. The humidity kept falling too low, I kept have to try to seal more edges of the box and eventually I started losing cigars.
I broke down today and bought a $40 humidor and in the space of just a few hours it is already keeping the cigars more moist and humid.
I failed. At least I only lost 3 cigars out of the 15 or so I had in there.
Of course, I bought 14 more today.