HVAC Mould: WorkSafe QLD Recognises IICRC S520 and AIRAH Best Practice

WorkSafe.qld.gov.au outlines a safety and prevention measure for the management of mould, categorised under Hazardous exposures, it specifies the control measures that can be taken to manage risks and protect workers' health, safety and wellbeing. Managing mould [1] refers to 1 Act and 2 recognised Standards in place for keeping yourself and others safe. They are: WHS Act 2011 [2], ANSI/IICRC Mould Remediation [3], AIRAH HVAC Hygiene Best Practice [4].

The WHS Act relates to the responsibly of an employer, building manager or owner, to provide a safe working environment to occupants, and the other two standards specify the procedures in place for the safe remediation of mould within indoor environments and HVAC systems.


Here's why HVAC Systems are an important consideration in all mould remediation projects and how they are decontaminated.


A poorly maintained HVAC System leads to performance, humidity and temperature control issues, and in turn, health risks.

Heating, Ventilation, Air Conditioning and Refrigeration (HVAC-R) Systems are essential for climate control within commercial buildings or storage facilities and in order to operate safely and efficiently they require scheduled cleaning and mechanical servicing. Poorly maintained HVAC systems lead to performance, humidity and temperature control issues and this results in harmful contaminants being spread throughout the building, presenting a health risk to the people inside.

Unmaintained HVAC systems circulate allergens like dust and mould. Mould accumulates as biofilm on components, this causes excessive condensation in the ductwork and produces mycotoxins which are then distributed within the breathing zone. Inhalation of these toxic mould spores can cause a range of issues, in some people the spores trigger an allergic reaction, whereas others may develop mild to serious lung infections. 

ABOVE Types of Mould Commonly Cultured from HVAC Systems

Learn more from Clean-Air's 'Microbe of the Month' series which outlines health risks associated with types of mould and bacteria cultured from HVAC systems, here

Maintaining safe Indoor Air Quality (IAQ) is most important in critical indoor environments such as Hospitals, Clinics and Aged Care Facilities. In hospitals mould spores along with bacteria and other contaminants contribute to deadly hospital acquired infections (HAI), also referred to as nosocomial infections. The Centers for Disease Control (CDC) estimates that 1.7 million nosocomial infections occur each year, with nearly 100,000 associated deaths [5]. Infants, pregnant women, the elderly, and any persons who have an immune deficiency are most susceptible to mould-related illnesses, but even healthy, young adults can become sick and as outlined by the Queensland Government, mould in the workplace is also a cause of serious concern, requiring immediate attention and action.

Certified remediation professionals can solve mould situations, making issues easier to control, or eliminating them altogether. This may include preventative measures and pre-planned maintenance (PPM) schedules.

If the HVAC system was overlooked during the remediation effort and mould remained in the ductwork, spores would continue to spread and colonise, regardless of the other cleanup strategies, so the air conditioner and ductwork should be a part of every mould inspection and remediation effort.


Tackling Mould Contamination in the HVAC System

Because the HVAC system can spread mould spores, it is best to clean the mould or remove contaminated components after completing remediation in other parts of the building. A remediation expert will be able to isolate the different areas so that mould does not spread to areas that are already clean.

Mould colonies within the system are cleaned using prescribed cleaning products specifically designed to target moulds, this might include anti-fungal or bio-enzymatic cleaners. Ductwork is typically non-porous and therefore easy to decontaminate with an appropriate cleaning agent. Only a professional can perform this task as ensuring every component and area of ductwork is treated correctly is critical.

ABOVE Mostly mould is hidden away inside ducting, unseen. By the time it reaches the vents and grilles, visible to occupants, it's a sure sign the whole system is contaminated.

This gluey matrix growing on HVAC evaporator coils, drain pans and ducts is, in fact, biofilm. Biofilm is an active, complex microbial matrix of mould and bacteria that adheres to HVAC components and protects the organisms from biocides.

While metal ducts will respond well to cleaning agents, other components within the HVAC system may require removal, this includes flexible ducting which generally cannot be cleaned. Typically, any porous elements and components that are difficult to cover with an anti-fungal agent need to be completely replaced. Cooling coils and evaporators are especially difficult to clean because of their shape and multi-layer designs. Other elements, such as fan blades and blowers, are cleanable if they have a smooth surface but need to be replaced if rough or porous.

There are different cleaning methods for removing mould. If you employ a specialist to remove mould from your building or facility, they have the ability to prescribe the appropriate approach to target a specific mould issue.

Vacuuming can remove mould particles. However, this method requires multiple passes over the same area in a cross pattern. A vacuum or other air-based method could be a solution for porous or semi-porous surfaces that are difficult to replace.

Liquid cleaners can include anti-fungal agents that can kill existing mould colonies and potentially limit new growth. An expert can select a cleaner that is safe for use in a ventilation system.

Abrasive cleaning measures may seem like a good solution. However, any method that scrubs the mould may cause the spores to become airborne and spread to other areas of the building. In general, using an abrasive method is not ideal unless you can place the components outside where airborne spores are less of an issue. A professional can clean an area of ductwork sealed off whilst under a negative pressure, removing debris and mould safely.

The best approach is usually a combination of the above. Using each method where appropriate, in some cases robotic cleaners are used to access hard to reach areas. See Muiltibot in action.

Additional Solutions to Mould issues within HVAC Systems

The methods that a remediation expert will suggest will depend on the cause of the mould and the extent of the contamination.

Modifications to the System may be necessary to address the cause of moisture problems. This could mean dealing directly with condensation inside the ductwork, near vents, or on mechanical components. In some cases, a dehumidifier can be used to lower the humidity within the duct system and throughout the building. 

Another factor is to ensure the ductwork is fully sealed and that areas with significant temperature contrasts have sufficient insulation; in addition to stopping condensation, extra layers can increase HVAC efficiency too.

One advanced sealing method that can be used is called Aeroseal. Performing Aeroseal Duct Sealing can seal the ductwork from within the system with minimal disruption, and complies with AS4254.2 2012 which states that rigid ductwork should not leak more than 5% at an airflow of 3000l/s and above, helping solve persistent contamination, mould, mildew and odour issues.

In addition to performing preventive maintenance, building owners can consider upgrading the HVAC filtration system. Better filters can support better IAQ and also prevent future contamination.

HVAC remediation experts may also offer an anti-microbial coating or sealant that can inhibit future mould growth. These products should be approved specifically for this purpose. They should also be non-toxic and safe for use in a ventilation system.

Another proven tool is Germicidal UV-C. The C wavelength of the UV spectrum targets the DNA of microorganisms, destroying their cells and making replication impossible. Directed at a cooling coil or drain pan, UVC energy destroys surface biofilm, a gluey matrix of microorganisms (bacteria, fungi, debris, et al.) that grows in the presence of moisture. UV-C also destroys airborne viruses and bacteria that circulate through an HVAC system.

Likewise, ozone generators can produce high concentrations of ozone (O³) gas within an enclosed space. When the ozone gas reaches a specific concentration for a specific exposure period it kills bacteria, mould spores and fungi, and damages the cell wall and protein spikes of viruses neutralising them on all surfaces, all objects, all equipment and most importantly any micro-particles floating in the air and inside air ducts or air filters.


Measuring Success; Pre and Post Verification Testing Methods

Indoor Air Quality (IAQ) experts use a variety of methods for assessing mould within HVAC systems, they can perform pre and post verification measures to ensure the indoor air is safe. Sampling is carried out in a strategic way and may include, swab sampling, bio-tape lifts or bioaerosol cassette captures. Only a Mycologist, a Micro-biologist that is an expert in fungi and mould, can determine which moulds are harmless and which are a threat. The safest outcome is to minimise the presence of all moulds. Domestic cleaners / mould treatments are often only bleaches, which may change the appearance of mould but not destroy it, that's why understanding the chemistry is vital. Results of sampling determines the correct remediation process where they will use specifically formulated chemicals, multi-enzymatic cleaners and Anti-Bacterial coatings to ensure an effective outcome. Data collected from IAQ Testing allows them to prescribe a specific course of treatment and determine the correct remediation process. Without following a stringent process like this there is no guarantee that the chemicals or treatments being used would be effective in solving an IAQ mould issue.


The Importance of Ongoing Maintenance

Regularly scheduled duct and HVAC cleaning can help lower the risk of future mould infestations. Maintenance can include ensuring the effectiveness of dehumidifier equipment and inspecting for air leaks or loose insulation. As well as protecting against mould growth, regular cleaning and maintenance can limit the spread of other allergens, such as dust, and ensure that the HVAC system operates at peak efficiency.


Choosing an expert protects the health and safety of the people in your building

With the multitude of factors involved, mould remediation for HVAC systems requires that you commission a certified team of experts with the knowledge and skills to deal with mould problems in climate control and ductwork systems. Choosing the correct cleaning agent, identifying components for complete removal, and making mechanical and structural upgrades to prevent further growth in the future can ensure a successful remediation outcome.

[1] https://www.worksafe.qld.gov.au/safety-and-prevention/hazards/hazardous-exposures/biological-hazards/managing-mould [2] Work Health and Safety Act 2011  [3] Standard and Reference Guide for Professional Mold Remediation, ANSI/IICRC S520 [4] HVAC Hygiene Best Practice Guidelines, Australian Institute of Refrigeration, Air Conditioning and Heating (AIRAH) [5] https://www.patientcarelink.org/improving-patient-care/healthcare-acquired-infections

Safe indoor air from a serviced HVAC system means a lower particle count and less breathing difficulties for occupants of the building. Clean-Air are IICRC mould remediation experts with the knowledge and experience to test, treat and eliminate serious mould-related risks within your HVAC system. Here's more information on our Mould Remediation services for HVAC Systems. If you have concerns about the air in your building and would like an HVAC health check, contact our team today.