The easiest way is to look at a profesional dry filter stack first to learn how a filter stack is usually made. So, let me grab my Dyson vacuum cleaner. On the intake side I get the following stack:
- large particle trap
- foam filter for medium particles
- HEPA filter
Incidentally, that's the same setup as my Shop-Vaccum has (though the foam filter gets replaced by a paper bag)
When I googled other dry filters, I found these filter stacks as common:
- large particle wavy paper filter then combined Carbon-HEPA filter (carbon first)
- 2 x Nylon-Mesh, Carbon, HEPA
The idea is to reduce the particulate grain the deeper you go into the filter. The rough filter is cleanable, the carbon filter traps chemicals and odor that might damage the HEPA filter, the HEPA filter catches any remaining particles.
If you want to know more about various filter types and applications, you might want to read an article on engineering 360.
Carbon dust is not not harmful - it is both flammable to explosive, as well as resulting in Black Lung (Coalworker's pneumoconiosis) if it is thrown into the air like in a mine.
However, commercially produced carbon filters don't usually release any coal dust: after making the activated coal, the product is shaped (as you can see in this manufacturer video) and sorted into various grains, like in the photo below. These granulate are then put into the carbon filter and trapped in a mesh that is small enough to keep them even after having been broken apart some. Very fine grains like the Bead Barbon are usually used in wet applications.
In a kitchen, you have sticks of 3-4 mm diameter, often trapped in a metal mesh. ABC-Mask filters usually use very porous carbon-grains in the half to millimeter grain size, trapped between paper sheets.