@nshapiro and I are working on a card upon which you can place a colorimetric tube for detecting formaldehyde, and take a photo of it to record data. Nick sent me the above sketch, and I doodled a design idea below. I figured we could prototype this idea out and further develop it in this research note.
Nick - do you have a typed list of all the info we'd want to include? Here's a diagram of the tube itself which is quite nice, from the company which makes it, Kitagawa:
And the PDF where I found the graphic: 710_1.pdf