Bathroom exhaust fan (homes) — cleaned and checked per service (per fan)
Added to an annual package (ready, custom or institution); not sold on its own.
Cleaning the bathroom exhaust fan and checking that it works.
Unit: per fan. The price is per service; quantity = number of fans × times a year.
Carried out during your annual subscription visits; the engineer confirms the numbers at the first visit: any excess is charged and any shortfall refunded. The price is fixed for the subscription year.