What this video covers
The clip covers why mold in an apartment building is rarely confined to one unit.
Units share wall cavities, plumbing runs and often ventilation. Water damage originating in one apartment travels through those shared elements, so neighbouring units can be affected without anything visible appearing in them.
The takeaway
If a neighbouring unit has had water damage, your unit is worth checking regardless of how it looks. Shared construction means shared exposure.
Read the full written guide: Mold in Rental Property and Health.