To limit the probability that the cross-sectional area of the ductwork will be reduced by crushing, which could lead to a reduced volume of air distribution in the ductwork, which could lead to:
This is to limit the probability of negative effects on the air quality of indoor spaces, which could lead to harm to persons.
To limit the probability of excessive sagging, movement or vibration, which could lead to:
This is to limit the probability of the generation of pollutants from biological growth, which could lead to negative effects on the air quality of indoor spaces, which could lead to harm to persons.