The heating, ventilation and air conditioning (HVAC) system in my workplace was shut down while COVID-19 restrictions were in place. What are the risks to health and safety once it is restarted?

Restarting HVAC systems that have been temporarily shut down can carry significant risks to the health and safety of workers and other people that enter the building, if they have not been maintained and inspected in accordance with relevant regulations and standards prior to restarting. 

During periods of shutdown, cooling towers and condenser water systems in an HVAC system can build-up corrosion on the surfaces that have not been chemically treated.

When an HVAC system is shut down, the sections of the system that have been altered, abandoned or capped so that water cannot flow through (dead legs) can hold stagnant water. The bacterium Legionella can grow in the corrosion build-up and dead legs. Legionella can cause Legionellosis. This condition includes Legionnaires’ disease, a serious infection in the lungs that can be fatal.

For further information on Legionnaires’ disease, you can also refer to the website of the health department in your jurisdiction. You can find out more about the risk of Legionella in an HVAC system during a period of shutdown at the Australian Institute of Refrigeration, Air-conditioning and Heating (AIRAH) website.

Occupants and other visitors returning to the building may also face health risks from inferior indoor air quality and mould if the hygiene of the HVAC system has deteriorated while shut down. Inadequate ventilation could also increase the risk of COVID-19 transmission at your workplace.  Further information on the role of ventilation to minimise the risks of COVID-19 can be found in at the Improving ventilation in indoor workplaces: COVID-19 webpage.

As an employer, what steps should I take to eliminate or minimise risks arising from restarting an HVAC system?

Before workers and other people enter a building where the HVAC system has been temporarily shut down, you must take all reasonably practicable steps to ensure risks to health and safety are eliminated or minimised. 

Occupants and other visitors returning to the building may face health risks from inferior indoor air quality and mould if the hygiene of the HVAC system has deteriorated while shut down. Inferior indoor air quality could also increase the risk of COVID-19 transmission at your workplace. 

You should ensure that HVAC units have been maintained appropriately to eliminate or minimise these risks before your workers enter the premises. You can consult with a qualified ventilation engineer and arrange an inspection if required. 

If you do not directly control or manage the HVAC unit you will need to liaise with the building owner or facilities manager to ensure that it has been maintained appropriately.  Your building owner or facilities manager should be able to provide a statement from a ventilation engineer that the system has been inspected and maintained.  

Complex HVAC systems, such as those that can transfer heating and cooling to secondary units or are integrated into the Building Automation System, can be more complicated to start up. In these cases, the building owner or facilities manager should consult a mechanical or ventilation engineer to implement the correct start-up procedures, to check control settings and to compare the system’s operation with commissioning baseline data. if your building has a complex HVAC system, you should confirm with the building owner or facilities manager that this has taken place before you allow your workers to enter the premises.
 

Can COVID-19 be transmitted through the HVAC system in my building? 

The Australian Health Protection Principal Committee (AHPPC) advises that COVID-19 can be transmitted via:

• fine respiratory droplets and aerosol particles
• direct physical contact
• fomite / indirect contact transmission routes.

Aerosol transmission of COVID-19 can occur particularly in indoor, crowded and inadequately ventilated spaces, where infected persons may spend time with others. The World Health Organization (WHO) advises that the risk of COVID-19 spreading indoors may be reduced through well-designed, maintained and operational ventilation systems. Proper use of natural ventilation may provide the same benefits. 

The importance of different routes of transmission for COVID-19 is an ongoing area of research, and the specific risk of transmission of COVID-19 through ventilation systems is not clear. However, poor indoor air quality may increase the risk of transmission. 

Currently there is no conclusive evidence that viable virus has been transmitted through an HVAC system resulting in disease transmission to people served by the same system. The US Centers for Disease Control and Prevention report that “viral RNA has reportedly been found on return air grilles, in return air ducts, and on HVAC filters” but that the presence viral RNA does not mean that infectious virus was present.  

Further information on the role of ventilation to minimise the risks of COVID-19 can be found in at the Improving ventilation in indoor workplaces: COVID-19 webpage.

I own an HVAC maintenance business, are there additional safety measures that I should implement to protect my workers when they are working on HVAC systems?

Workers involved in servicing HVAC systems should abide by all industry safety regulations and standards, including wearing all necessary personal protective equipment. 

As an employer, to reduce risks such as COVID-19 in the workplace, you must:

• undertake a risk assessment for your business (more information is available on the risk assessment page and the Model Code of Practice: How to manage work health and safety risks), which should consider the specific workplace setting. For instance, maintaining a hospital HVAC system where COVID-19 patients are being treated may have different risks to maintaining other systems. 
• consider the available control measures and how they will help manage the risks of COVID-19 
• consult with workers and Health and Safety Representatives about COVID-19 and relevant control measures, and
• determine what control measures are reasonably practicable for you to implement for your work and in your workplace.

Employers must also continue to implement all reasonably practicable control measures to minimise the risks of COVID-19, such as:

• encouraging or ensuring vaccination , where applicable
• ensuring your workers do not come to work when unwell
• practising physical distancing and adhering to density limits (check occupancy limits for the type of building and building standards)
• relocating work tasks to different areas of the workplace, off-site or supporting workers to work from home
• practising good hygiene
• increasing cleaning and maintenance
• staggering your workers’ start, finish and break times
• reducing the number of situations where workers come into close contact, for example in lunchrooms and other shared spaces, and
• wearing face masks.

For further guidance on how to help minimise the risk of COVID-19, you can refer to our guidance for the Trades and home maintenance sector or the Energy and utilities sector.