To limit the probability that an inappropriate design will lead to an inability to accommodate movement due to shrinkage, settlement, or temperature- or soil-related expansion and contraction of vent pipes in DWV systems, which could lead to the failure of pipes, joints or fixtures, which could lead to leakage, which could lead to the entry of sewer gases into occupied space, which could lead to negative effects on indoor air quality, which could lead to harm to persons.