Re ECF Project: ECF 2015-89

Project Title: What makes an odorous air conditioning system in Hong Kong?

Applicant: Dr Lai Ka Man, Department of Biology, Hong Kong Baptist University

Total Approved Grant: $496,240 (ECF & WWGF: 50/50)

Duration: 1/5/2016 to 30/4/2018

Project Status/Remarks: Completed

This is a laboratory and field based study focusing on the microbiological aspect of air-cooling units. The project aims to:
(a). identify the odour-causing bacteria and pathway;
(b). determine the inhibitory factors for these bacteria and pathways;
(c). study the formation and inter-relationship of the bacterial communities; and
(d). apply the findings in the field study and test the effectiveness of different control measures.

Summary of the Findings/Outcomes:
Air quality in indoor environments is associated with people’s health and well-being and should be given due attention since many Hong Kong people spend more than 70% of their time indoors. It is commonly believed that odour problems are due to a dirty air-conditioning system. However, this study found that odour was reported from clean air-conditioning systems. Skin squames shed from the human body can provide nutrients to the bacteria and contribute to ammonia (urine-like smell) and volatile fatty acid (body odour) production by bacteria colonising air-cooling units. For effective long-term odour control, it is important to reduce the amount of skin squames from entering the air-cooling units. To do so, the simplest way is to install an appropriate filter to capture the skin squames. This study revealed that Staphylococcus species emitted from the air-conditioning system may hint to a potential odour-causing unit. Installing an appropriate filter to air-cooling units has successfully mitigated odour problems in the field. The Principal Investigator of the project gave a presentation at the Indoor Air Quality Certificate Award Ceremony (2016) organized by the Environmental Protection Department and a press conference was organized at HKBU in January 2018. In practice, the approach to reduce organic loading in the air-cooling unit has solved the odour problem in a government clinic in Ap Lei Chau.