carbon filter

Yeah, since the object is to filter as much odour as physically possible from the air that's extracted from your grow-room, you really are better off with a commercial model that's been engineered to do the job.

As far as carbon being a hazardous material, I think it's about as neutral as you can get if you eat it (and it's a good absorber of toxins), but you wouldn't want to breathe micro-particles of it for 8 hours a day, if your job is to construct the filters.

I think all tiny particles can have horrible effects if you breathe them for significant periods of time. Asbestosis is an extreme example, but I think exposure to sawdust, flour, cement and any other airborne dust can kill in the long term.

Possibly, the effect of breathing carbon particles for many years would be like 'black lung' suffered by coal miners.

And don’t get me started on the potential hazards of rockwool dust. Just be sure never to work with it when it’s dry. When wet, you can tear it without creating a cloud of glass-fibres.