We are experimenting with cheap and simple HECA assemblies for colder climate, feel free to critisize and ask questions.
The SDS011 sensor orientation on the photos is wrong, we know it.
Stainless Steel Scourer great!
There are fancier heatsink designs by Viktor Antonóvich and it is an open question which one is better. To my heart they are too complicated.
First of all - Stainless Steel Scourer - very nice idea. However tests should be made because of potential static charge build up. It may attract smaller particles and act as filter.
Also I see no exhaust port in your design. You will build up positive pressure in your enclosure. So your reading will be way too low because of insufficient airflow.