HSE explains that mechanical ventilation brings outside air into a building through fans and ducts. Moving or cooling air already inside a room does not by itself demonstrate enough outside-air supply. Check the actual air routes before judging ventilation.
Understand the components
Fans move the air through the unit and ducts. Their condition, settings and operating point affect what reaches the rooms.
Filters collect airborne particles and need maintenance appropriate to their type, condition and replacement arrangements.
Coils exchange heat when the unit includes heating or cooling. The water or refrigerant system serving them also affects the result.
Controls and any heat-recovery parts vary with the installation. Not every unit has the same components; Daikin's AHU configurations illustrate different combinations.
Investigate the whole system
Weak airflow, unexpected noise, poor temperatures or repeated alarms need investigation beyond the unit alone. Ducts, room terminals, controls and connected equipment can change the outcome you notice indoors.
Give the model details, operating hours and past findings. Explain whether the problem affects every room served or only some areas, helping the contractor distinguish equipment, control and distribution issues.
Prepare maintenance access
Make room for the actual work: inspection, changing filters, cleaning, repairs and checks. Discuss roof or plant-room access and any loss of service before arranging attendance.
Keep a report identifying the unit, components, work and findings. It should tell you whether something was replaced, a defect was found or more investigation is needed, with the next steps clear.
Check performance after changes
After parts or controls change, ask for suitable functional checks and updated records or settings. Changes to distribution may need air balancing as well.
FAQs
Is an AHU the same as an air-conditioning unit?
The labels refer to different equipment arrangements. An AHU moves and treats air, and may receive heating or cooling from other plant. Check your system’s design.
Does an AHU always supply fresh air?
Do not assume so. Its air paths and controls determine how much outside air and recirculated air it handles.
What information helps with an AHU fault?
Send the unit details, symptoms, fault messages, hours of operation, affected rooms and any recent maintenance or setting changes.
Related services
See Air-Handling Units, Ductwork or HVAC Maintenance and Servicing. To discuss your equipment, describe the equipment and what has changed in the spaces it serves.
Other information is available through all services, maintenance, projects, sectors, locations and the knowledge centre.
