Air Conditioning Cleaning:

Why it should get done.

air conditioning making you sick?

Can the air conditioning make you sick? Media coverage of Building Sick Syndrome and Legioneairs Desies are extreme examples of illness spread by the air conditioning systems and are the exception rather than the norm. 
While links between low air ventilation rates and increased raspatory disease exist, poor air conditioning hygiene is more likely to impact on the Indoor Air Quality (IAQ). Poor IAQ can cause allergy response in susceptible individuals, stresses to the immune system, and result in higher CO2 rates. Elevated CO2 will cause headaches, loss of concentration and a decline in productivity for the building occupants.
Poor hygiene impacts the performance of Heating, Ventilation, and Air Conditioning (HVAC) equipment. Energy efficiency, the economic service life of assets, cooling and heating capacity, and equipment reliability degrade over time when effective inspection and cleaning methods are missing from regular maintenance. Poor hygiene of air handling equipment in Comercial HVAC may also impede the fire and smoke handling of mechanical services in fire mode.

Air Conditioning Cleaning. Why?

Air conditioning filtration is never 100% efficient if it were air would not be able to flow through the filter.

So, with that in mind, it is understood that some contaminants will bypass the filter and collect within the air conditioning apparatus, particularly the indoor coil. The air conditioning indoor coil can become restricted within a four year ‘fouling time’ (Krafthefter B., 1987). With soiling of the coil, the airflow and the cooling process is compromised, and the equipment will no longer operate efficiently.


HVAC Hygiene

Mould colonisation in buildings has a long association with problematic health for occupants (Institute of Medicine, 2004).

During the warmer months, the air conditioner will condense moisture from the airflow onto its indoor coil. The indoor coil is the heat exchanger between the airflow and the cooling refrigerant that cycles between the indoor and outdoor air conditioning equipment. The moisture and dust then support mould colonisation, biofilms, and bacterial growth. These microorganisms can proliferate to restrict or block the air conditioning condensate drain leading to water spill and damage to the building.

Furthermore, mould spores entrained in the airflow cause allergic reactions and stress occupants’ immune system. Illness from bacteria and viruses in air conditioning are less common but can become life-threatening in unique cases. (The 1976 legionella outbreak at the Pennsylvania Department of the American Legion convention, and naming of legionella disease).

Indoor Air Quality & Dilution.

Excessive build-up from people’s respiratory carbon dioxide (CO2) in an enclosed space will cause loss of mental acuity, as well as headache, nausea, and giddiness.

Interestingly, many Australian classrooms with wall mounted split air conditioning have no outside are dilution when the windows are shut. Yes, these split air conditioners need to be run with the windows open to allow adequate ventilation. (Daily Telegraph, 2019).

With engineered-designed air condition, provision is made for building ventilation and dilution of the indoor air. Outdoor air is drawn through the air conditioning equipment and mixed with indoor return air before being conditioned and supplied to the indoor space. As the air conditioning indoor coil and filters become more soiled, the airflow through the equipment reduces. When outside ‘makeup air’ is fitted to the air conditioner, a reduced airflow will reduce the amount of fresh air dilution for the conditioned space. Reduced dilution will degrade the indoor air quality and increase the particle count of contaminants such as CO2. Reduced fresh air dilution is concerning for the health and wellbeing of occupants of places of business, education, and public amenities. There is also a requirement for Heating and Ventilation and Air Conditioning (HVAC) classified within The Building Code of Australia (BCA) and under the Environmental Planning and Assessment Regulation to meet minimal rates for indoor air dilution and ventilation.

There are other air quality contaminants released by the structure and materials used in the building. The off-gassing of organic compounds such as formaldehyde in insulating foams, carpets, practical board, and clothing will cause eye irritations, headaches, nausea, and respiratory complaints when air changes with outside air dilution are inadequate.

There are strong links between low air ventilation rates and increased raspatory disease (Li, 2007) such as influenza. It’s also been shown that increasing building ventilation reduces the number of short term absences from office staff (Milton, 2000)and elementary school students (Shendell, 2004). So it would appear that inducing more fresh air through the HVAC equipment will help to reduce the occurrence of some airborne diseases.

In general, the CO2 levels in the conditioned space is a good indication of the indoor air quality. In ensuring a healthy indoor environment, the CO2 levels, design airflow rates, and air conditioning hygiene should be inspected and measured regularly.

Energy Efficiency

Heavy soiling of air conditioning equipment can reduce your cooling capacity by 20% while increasing your power consumption by 30% (AIRAH).

Soiling of air conditioning indoor coil builds up over time and will reduce the total airflow through the equipment. With reduced airflow, there is a reduction in the air conditioning capacity to cool with an increased power consumption due to inefficient operation.

Simple modelling can demonstrate that moderate soiling can have a 20% penalty on energy consumption (Coil Clean Services). If left unresolved, there will be an expediential rise in efficiency losses over consecutive years.

With the inefficient operation of the air condition equipment there will be an increase in equipment failure and associated cost due to equipment downtime and repair costs.



AIRAH, n.d. [Online]
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Coil Clean Services, n.d. [Online]
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Daily Telegraph, 2019. School aircon: Sickness link to carbon dioxide. 5 July.


Institute of Medicine, 2004. Damp Indoor Spaces and Health. s.l.:National Academies Press.


Krafthefter B., R. D., 1987. Air-Conditioning and Heat Pump Operating Cost. ASHRAE Transactions, Volume Vol. 93, pp. 1458-1473.


Li, Y., 2007. Role of ventilation in airborne transmission of infectious agents inthe built environment – a multidisciplinary systematic review. Indoor Air, Issue 17, pp. 2-18.


Milton, D., 2000. Risk of sick leave associated with outdoor air supply rate, humidification, and occupant complaints.. Indoor Air, Issue 10, pp. 357-376.


Shendell, D., 2004. Associations between classroom CO2 concentrations and student attendance in Washington and Idaho.. Indoor Air, Issue 14, pp. 333-341.


The author, Daniel, is a mechanical tradesperson with over fifteen years of experience in the air conditioning and refrigeration industry. His role at Coil Clean Services is to create customer value by delivering site-specific and performance-driven maintenance for refrigeration and air conditioning coils and heat exchangers. Coil Clean Services is an air conditioning, and refrigeration contractor based in Sydney Hills District specialising in air conditioning and refrigeration coil cleaning. They are fully licensed for all HVAC&R work and can provide additional maintenance, and repairs on the full extent of heating, ventilation, air conditioning and refrigeration systems.

Coil Clean Services has the equipment and knowledge to successfully clean commercial and residential air conditioning equipment and validate there work.


We can measure and report back on improved airflow and air dilution as well as organise independent laboratory test for air conditioning mould and biofilms.


We are licenced refrigeration and air conditioning contractors and can fully complete repairs and remedial works on all HVAC&R equipment.