MDF and non-laser ply, anything with glue or resin in it will block the filter faster than you can say Makerspace.
We did a test, on a project early on and the machine became very dirty, much of the brown discolouration is because of that project. The machine was very sticky inside also. This also increases the risk of breaking the lens from residue on the lens that needs cleaning off.
Importantly: The fumes from the MDF go through the filter into the room leaving an acrid smell that I found left me with itchy skin and eyes, sore throat, triggered my asthma and a headache on the several occasions when it was being tested.
I understand the desire to use MDF but normal non-Laser MDF certainly is banned and if you wish we can have a meeting and demo of why this is the case with other interested parties, however we’ve already tested MDF, it was one of the first things we tested.
While most public places will laser MDF, that is at their own risk and doesn’t mean that it is best practice, none of the colleges I’ve worked at or visited including, all 5 colleges of University of the Arts, University for the Creative Arts, and Royal College of Art.
Also FYI: The lens in our laser cutter can’t focus materials greater than 12mm so it is impossible that 18mm be cut.