Ventilation system - air distribution box accessible

Hello everyone,

we have a question: Are the air distributors for the supply/exhaust air pipes generally accessible at your place, and do these boxes have an inspection opening?

For example, I have read in the Vallox planning manual that the boxes must have an inspection opening according to DIN 1946-6. That means the air distributor boxes should generally be accessible, right?

Our air distributor boxes for the ground floor and upper floor are housed in a room where the ceiling has been suspended. I can’t easily access them there if something happens or if the pipes need to be cleaned.

We decided back then to install filter bags in every exhaust vent (before balancing) due to structural obstacles, which keeps the piping clean.... Otherwise, there are now certainly several providers with different cleaning approaches (compressed air, ......) From that point of view?