Tani waa hordhac kooban oo ku saabsan qolka bandhiga cusub.Alaabooyinka ugu muhiimsan ee la soo bandhigay waxaa ka mid ah hawo ku beddelasha kulaylka hawada, kuwa hawada ka saara, hawo-mareenada ka soo kabashada kulaylka HRV, hawo-mareenada soo kabashada tamarta ERV, unugyada jeermiska hawada, unugyada hawo-mareenka, iwm. Waxaan haynaa noocyo kala duwan oo ah alaabta xalalka hawada si loo buuxiyo shuruudaha codsiga kala duwan.