The AIRAH Guideline DA27
In Australia, the AIRAH (Australian Institute of Refrigeration, Air Conditioning and Heating) publishes DA27, which provides guidance on HVAC hygiene. It recommends visual inspection annually and cleaning when contamination exceeds acceptable levels—typically measured by dust loading per 100cm² of duct surface.
NADCA ACR Standard (International Reference)
The international NADCA standard (ACR) is often cited and suggests cleaning every 3-5 years for general commercial buildings. However, for food processing or healthcare environments, a 2-year cycle or more frequent is common due to higher hygiene requirements.
Signs You're Overdue
- Visible dust or debris on diffuser grilles.
- Musty smell when the system starts up.
- Increased energy consumption without other explanation.
- Staff complaints about "stuffy" air or allergies.
ProSan Australia offers free visual duct inspections with borescope photography to assess your system's condition.