Some building materials expel VOC (volatile organic compounds).
Even working during  the  construction like sawing indoor generates dust.
The German monitoring agency Sentinel shows us their concern on the matter of VOC’s. Their approach with spectrum analyses on the spot is in depth but at this moment too expensive for individual costumers.
From experience we know that some people  are allergic even to natural materials, like to citrus components in natural paint products. Fortunelately there are p.e. anti-allergic paint products.

Such sensitivity can be discovered by tests like Vegatest and Quintium.
Tubes of mechanical ventilation neet to be cleaned every year. Professional cleaning will be obliged very soon. On the other hand filters against  pollen can be placed in this system, but in decentralised ventilation systems without these long tubes this is possiible as well.