What lurks beyond: Inspecting HVAC systems’ inner cleanliness

by FM Media
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JEREMY STAMKOS from Total Ventilation Hygiene provides insight into internal cleanliness inspections of HVAC systems – why should they be conducted and what is best practice in this regard?

Whether it’s periodical inspections in line with Australian Standards, an inspection to find the source of indoor air pollution or a post cleaning inspection to verify cleanliness, HVAC hygiene inspection and reporting can prove to be an extremely valuable service for all concerned.
More than 50 percent of all indoor air quality (IAQ) issues are directly related to HVAC systems. Conducting regular internal inspections of HVAC systems to verify their cleanliness can help combat this.
Although the majority of these issues are generally related to a lack of ventilation causing a high concentration of indoor airborne pollution, the actual HVAC system itself can be responsible for spreading high levels of contamination into the occupied areas of a building. The deterioration of internal surfaces, such as rusting metal surfaces, and deteriorated internal insulation are common sources of HVAC contamination.
Contamination of HVAC systems can affect the health and comfort of building occupants, and compromise the operational efficiency of the systems.

In order to provide guidance on maintaining HVAC system cleanliness, Australian Standard AS/NZS 3666.2 stipulates regular inspection intervals for specific HVAC system components, while the Australian Institute of Refrigeration, Air-conditioning and Heating’s (AIRAH’s) HVAC Hygiene Best Practice Guidelines provide detailed information on how to conduct inspections and identify when an HVAC system requires cleaning.
Building owners and managers have a duty of care to building occupants to ensure that a building complies with regulations relating to the maintenance of its HVAC systems. Compliance with the relevant Australian Standards, along with industry best practice guidelines, help meet this obligation and help ensure that the health and safety of building occupants is being properly addressed.
Most building owners and managers (rightly or wrongly) rely heavily on their mechanical service contractors to ensure that the HVAC systems in their buildings are maintained at a satisfactory cleanliness level. It is very rare that the specific responsibility of maintaining the cleanliness of a building’s HVAC systems is stipulated in a maintenance contract with a mechanical services company, but it is common for the systems to be maintained in accordance with Australian Standard AS/NZS 3666.2.
Unfortunately, due to a lack of knowledge, and even complacency sometimes, mechanical services contractors may not conduct regular cleanliness inspections in line with the Australian Standard and industry best practice guidelines. Some contractors may also be reluctant to conduct HVAC hygiene inspections for fear of reprimand over the unhygienic state the system may be in. This is generally the case when a mechanical service contractor has been the incumbent service provider for some time and the internal cleanliness (or lack thereof) of HVAC systems may be seen as a reflection of the level of services provided.
By conducting regular hygiene inspections, HVAC system cleanliness is better maintained, as any potential cleanliness issues are identified early and often avoided. Regular maintenance activities, such as coil cleaning, minor cleaning and filter maintenance, all help to maintain HVAC system hygiene. Regular attention to internal HVAC cleanliness and conducting cleaning as required will also help avoid major contamination events within the system and the building as a whole.
Due to HVAC filtration in most buildings being fairly average at best, nearly all HVAC systems will eventually require cleaning. Even a well-maintained HVAC system with regular air filters will most likely need cleaning after 10 to 15 years, while some systems may go for more than 20 years without requiring cleaning.
This is dependent on many factors, including, but not limited to, the design of the HVAC system, the level and placement of the filtration system, the type of areas serviced by the system and even the geographical location of the building.
Some building owners and managers bypass their mechanical services contractor and directly engage HVAC hygiene specialists to conduct the required HVAC cleanliness inspections and reporting. This will generally provide an accurate evaluation of the HVAC systems’ cleanliness levels and allow the planning and scheduling of any required remedial or cleaning works to begin.
The best way to properly manage the cleanliness of a HVAC system is through conducting regular HVAC cleanliness inspections as per Australian Standard AS/NZS 3666.2 and using industry developed guidelines, such as the AIRAH’s HVAC Hygiene Best Practice Guidelines.
If an HVAC cleanliness inspection reveals that certain components of a system require cleaning, a detailed and specific scope of works can be developed based on the findings of the report.

To help address the risk of microorganisms in air-handling systems, a new addition to Australian Standard suite AS/NZS 3666 was released in late 2011. Part four of the 3666 series incorporates performance-based maintenance of air-handling systems (ducts and components) and outlines a performance-based approach to the maintenance of air-handling systems with respect to the control of microorganisms.
It is an alternative to the prescriptive requirements of AS/NSZ 3666.2 (Clause 2.3.5) for the maintenance of air-handling systems other than those incorporating water-supplied devices, for example, humidifiers and evaporator coils. By following AS/NZS 3666.4, you will also be in compliance with AS/NSZ 3666.2 (Clause 2.3.5).
Compliance with the new standard is a four-stage process comprising the following steps:

  1. stage one: on-site assessment – on-site assessment of air-handling systems by a competent person
  2. stage two: evaluation and reporting – evaluation of the risk of growth and spread of microorganisms and completion of a report using risk matrix and classification procedure to form part of the building owner’s facilities management reporting system
  3. stage three: implementation of compliance –rectification works undertaken and the maintenance policy updated, and operating and maintenance manual, and
  4. stage four: verification of rectification – development of a compliance schedule for any required rectification works and verification of completion by the required time-frames.

Once HVAC systems are deemed to be compliant, an audit does not have to be repeated for a period of up to five years. This is dependent on the fact that there are no major changes that would affect the HVAC systems.

Many major HVAC cleaning projects are conducted as either part of a building refurbishment project or in response to specific contamination concerns. It is becoming common practice to specify cleaning for any HVAC system or component not being replaced during major refurbishment projects.
Unfortunately, most of these major HVAC cleaning projects are conducted without a detailed HVAC cleanliness inspection being conducted prior to the project. This results in HVAC systems being cleaned unnecessarily. If a thorough HVAC inspection and report is conducted, only cleaning of the HVAC system’s components that actually require cleaning are cleaned, saving a significant amount of money.
While the average HVAC cleaning projects range from $5000 to $20,000, there are many projects in excess of $50,000. Due to this investment being rather significant for an ‘unseen’ result (unlike other products and services, clients rarely see the cleanliness of the systems after a project is complete), it is important to know good value for money is being received.
Due to the internals of the HVAC system being difficult to access and inspect, the credibility of the HVAC cleaning contractor is generally relied upon to ensure that the company accesses and cleans all of the HVAC system’s components as specified or as quoted. However, third-party consultants or contractors can be engaged to undertake post cleaning verification inspections to evaluate if the HVAC cleaning has been done properly. This provides an independent sign-off to verify the right level of service has been provided.

For smaller HVAC cleaning projects (say under $10,000), most HVAC hygiene contractors will conduct a ‘no cost’ HVAC cleanliness inspection as part of their quote. This will generally involve the contractor taking a few digital images of the dirtiest parts of the system they can find to include with their quotation in hope of winning the work.
Although some would argue that this is not the ideal situation, the conditions and sometimes value of the project may not justify conducting a full HVAC cleanliness inspection and report. For example, if the cleaning of an HVAC system is going to cost $2500 and it’s reasonably obvious that the HVAC system requires cleaning, it is unlikely that a full HVAC cleanliness inspection and report will be done.
For projects over $10,000, consideration may be given to engaging an HVAC hygiene contractor or an independent consultant to conduct a pre and post works HVAC cleanliness inspection.
Pricing may vary significantly from one company to the next in regards to conducting such inspections. As an indication, a professional HVAC hygiene inspection and report may cost anywhere from $250 for an air-conditioning system servicing a small office space up to $5000 for an air-conditioning system servicing an entire commercial building.
If an HVAC hygiene contractor is engaged to do the inspection and has a fairly high probability of winning any resultant HVAC cleaning work, the price to conduct the inspection may be significantly lower than that of a contractor or consultant who knows they will only win the inspection and reporting work.
The danger with engaging the same contractor to do the inspection and to do the actual cleaning is that the building owner may not be receiving truly unbiased reporting. It is always recommended that, where possible, a contractor independent from the contractor providing HVAC cleaning works is used to conduct all HVAC hygiene inspection and reporting works to ensure unbiased reporting.

A significant cost of conducting HVAC cleanliness inspections can be the supply and installation of access panels to facilitate the inspection of the internal surfaces of the air ducts. In order to comply with the maintenance standards for air-handling systems, access panels are required in certain sections of the air ducts so that inspections of the internal surfaces can be conducted.
Unfortunately, most HVAC systems do not have these access provisions into the air ducts to conduct the internal cleanliness inspections and compliance with standards such Australian Standards as AS/NSZ 3666.2 and AS 1851:2005 cannot be fully achieved.
Installing access panels into air ducts should only be done by experienced and qualified technicians. Whether access panels, service doors or just plain sheet metal are used to seal inspection access points, it is imperative that the installation of access provisions does not compromise the thermal or acoustic properties of the air ducts or negatively impact the system in any way.

Australian Standards AS/NZS 3666.2 and AS 1851:2005 both stipulate the periodical inspection of certain HVAC system components to help ensure HVAC system cleanliness, efficient operation and that the systems do not pose a threat to occupant health and safety.
Building owners and managers are obligated to meet these requirements and should make sure that their maintenance staff or mechanical services contractors are undertaking the minimum HVAC inspections as per these Australian Standards. HVAC audits in accordance with the Australian Standard AS/NZS 3666.4 and the AIRAH’s HVAC Hygiene Best Practice Guidelines are highly recommended.

Jeremy Stamkos is a director of Total Ventilation Hygiene. Stamkos has more than 20 years of experience in the HVAC hygiene industry and is the convener of the AIRAH’s HVAC Hygiene Best Practice Guideline, which was published in 2009.

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