To limit the probability that inappropriate construction or installation will lead to an inability to flush or drain sumps for air washer and evaporative air cooling sections, which could lead to the accumulation of moisture or dirt in the air stream, which could lead to the growth of mould, mildew or bacteria, which, if circulated in the air stream, could lead to negative effects on the air quality of indoor spaces.
This is to limit the probability of harm to persons.