Do rental kitchens and bathrooms need extractor fans?

Yes. Under the ventilation standard, kitchens and bathrooms, the rooms that generate the most moisture, need mechanical extraction venting to the outside of the building. Openable windows alone do not cover these rooms, and newer fan installations also carry minimum performance requirements, specified in the official guidance by duct size or airflow.

The two silent failures

• Venting nowhere: a fan ducted into the roof cavity moves steam into the structure instead of out of the house. Extraction has to reach outdoor air, check the outlet exists and its flap moves when the fan runs.
• Spinning without extracting: age, clogged grilles and collapsed ducting can leave a fan making noise and moving nothing. A square of toilet paper held to the grille should stay pinned there while the fan runs.

Range hoods have their own trap

A recirculating hood filters air and returns it to the kitchen; it does not vent moisture anywhere and generally does not do what the standard is asking. Ducted-to-outside is the arrangement that counts. If you are unsure which yours is, run it and check for airflow at an external outlet.

Keep fan specifications and invoices with the property's records, and test every fan at routine inspections. The current performance details live on tenancy.govt.nz.