I got curious about the air quality sensor and did some digging. In particular I was curious about air flow, since all the AQ sensors I am familiar with (like PurpleAir) have fans, but this one does not.
Turns out the PPD42 uses a resistor that is heated to create air flow. For this to work, the sensor is supposed to be installed vertically, with the connector at the bottom. There are 2 vents. The open area in between the vents is supposed to be covered, opaquely.
I am working on a design for a new enclosure that follows these requirements. The easiest way to do this is to mount the sensor on the side of the box, rather than below, so I am going with that.
Keeping it dry is also one of my concerns. To that end I rethought my placement of the sensor, and have decided to design a box for it that attached to the bottom of the box (like the original housing). This is probably also better for anyone who has already drilled a hole in the bottom of the box for the AQI sensor cable.
Write up a description of your 3d prints and why you chose what you did. Give some installation instructions and a parts list of what you need. I'll get John to publish it both on the product page and in his blog, www.switchdoc.com