Air ducts are an integral component of your HVAC unit. They need cleaning from time-to-time because they gather dust, dirt, grime, and pollen. Moreover, the foot traffic in the office contains more allergic germs and dust that gets picked up by the HVAC and the circulated air obviously contains those impurities.
Smell emanating from vents, a screeching noise coming out of HVAC when it is on, difficulty in breathing, visible dust at the edges of the vent, symptoms like runny nose, headache, watery eyes sneezing because of the HVAC activation are signs that the ducts need to be cleaned.
