NMMT Bus are Dust chambers

Haven't travelled in bus route 20 for while so decided to travel on it Started regretting that decision in just 5 mins in travelling in bus Ac vents are completely filled with black soot type stuff aka haven't cleaned ac vents and are splitting out so much dust from vents Had to close ac went close to my seat cuz it was getting to uncomfortable Are all AC buses in NMMT route are like this ? Or its just this one