This is a guidance document on currently known best practice for, heating, ventilation, air conditioning (HVAC) and water systems, in relation to the coronavirus/COVID-19 (named SARS-CoV-2).

SARS-CoV-2 (“the virus”) is most likely to spread from within your building, rather than through supply or fresh air. Therefore, the removal of existing air and the introduction of fresh air into a building is essential in fighting the spread of the virus. This guidance informs, facility managers, maintenance personnel and building owners on how to operate HVAC and water systems, to help prevent the spread of the virus. This is applicable for non-clinical commercial and public buildings, i.e. where only occasional occupancy of infected persons are expected. To minimise risk of the spread of the virus in this context, there are three main practical measures to begin with.

1. Introduce full fresh air from outside.

2. Do not re-circulate existing indoor air.

3. If normal periodic planned preventative maintenance (PPM) has not occurred due business closure, it is recommended that maintenance procedures re-commence immediately.

Contents

Heating

Ventilation

> Non-mechanical ventilation

> Mechanical ventilation

> Toilet ventilation

> Heat recovery systems

> Filters

> Disposable air filters

> Plastic air filters (indoor air conditioning units)

Air conditioning

Water systems – Legionnaires disease

Safety

Novel enveloped virus

Planned preventative maintenance (PPM)

Key guidance source materials


Heating

Heating systems can operate normally and without adjustment, as the virus is tough and resilient, meaning changes to temperatures or humidity in the environment will not make much impact.


Ventilation

Recent studies on the virus have shown that crowded indoor environments with minimal ventilation are ideal places for the virus to spread. By introducing as much fresh air as possible, the risk of the virus spreading can be reduced.

> Non-mechanical ventilation

Buildings that contain no mechanical ventilation must utilise windows.

  • To help remove virus particles from the building environment and from surfaces, supply as much outside air as is reasonable possible.
  • Utilise openable windows, even if it causes thermal discomfort in the surrounding environment.

> Mechanical ventilation

Mechanical ventilation is a strong ally in fighting and limiting the spread of the virus in buildings.

  • To help remove virus particles from the building environment and from surfaces, supply as much outside air as is reasonable possible.
  • Switch air handling units with re-circulation to full fresh air or 100% supply air. Please note, this will lead to increased energy costs, however, this cost must be weighed up against the staff and public health benefits during a pandemic.
  • Supplement mechanical ventilation with the use of openable windows to boost ventilation levels.
  • Extend ventilation hours of operation to:

Before occupation – 2 hours before building usage at nominal speed. After occupation – 2 hours after building usage at low speed.

  • Demand-controlled ventilation systems should be kept on 24/7 and not switched off. However, ventilation rates can be lowered when there is no occupancy.
  • Cleaning of ducted ventilation is not an effective countermeasure, as the virus – when attached to other small particles – will not easily deposit in ducted ventilation systems. It is much more important to increase fresh air supply to 100% and halt the re-circulation of existing air.
  • If ducted ventilation cleaning is required as part of periodic maintenance, it should be carried out.

> Toilet ventilation

Faecal-oral transmission has been recognised by the World Health Organisation (WHO) as a transmission route of the virus, therefore, it is wise to implement the following precautions in toilets.

  • Care and consideration should be exercised around mechanical exhaust air flow from toilets to other rooms.
  • Toilet ventilation systems should operate 24/7.
  • If mechanical ventilation exists within the toilet, the use of openable windows should be avoided.
  • If no mechanical or exhaust ventilation exists, openable windows should be utilised to provide air flow into the toilets. However, it is important to open windows in other rooms in the vicinity of the toilets to get the air moving and achieve air cross flows.
  • With the virus being detected in stool samples, it is crucially important to ensure that it does not spread from toilets. Therefore, as a precaution, all toilet seat lids should be closed when flushing toilets to minimise the escape of virus plumes, aerosols or droplets. Aerosols and droplets containing virus particles are one of the most common ways the virus has spread.

> Heat recovery systems

Heat recovery systems are effective energy savers and work based on using the energy from extracted exhaust air in a building, to filter and condition incoming fresh supply air.

  • In standalone heat recovery units, the bypass function should be utilised to ensure maximum air changes are achieved.
  • In air handling units (AHUs), rotary or thermal wheel heat recovery systems are the most prone to leakages, due to poor design, installation or maintenance. In some cases, 20% of polluted extract air transferred and mixed with incoming supply, thus contaminating the room air.
  • Plate heat recovery systems – also in AHUs – are a much safer, as exhaust and supply air do not mix, however, failures can occur.
  • Therefore, it is recommended that heat recovery systems in AHUs are switched off at this time, due to the possibility of leaks or cross contamination.
  • It is prudent to have heat recovery systems inspected by a HVAC service engineers to prove their correct operation, without leakage.

> Filters

Air filters are an important protection measure in containing contaminants such as microbiological materials – including viable virus particles – and supplying clean air to building occupants.

> Disposable air filters

  • Upgrading of filters is not recommended during this time as, the naked virus particle is smaller (PM0.1) than the most efficient filter (PM1 rated) in non-clinical buildings.
  • Moreover, small virus particles will settle on filter media and aggregate with larger particles – already contained within the filter media – and halt the virus spread.
  • Also, when thinking about upgrading filters, mechanical seals and other considerations have to be taken into account – to ensure more efficient filters are viable in an existing system.
  • Only in rare cases does the virus enter via outdoor fresh or supply air therefore, standard filters are presumed a reasonable risk prevention measure.
  • If filter replacement is required as part of periodic planned preventative maintenance (PPM), then PPM should be carried out without delay. Clogged or blocked filters will reduce fresh supply air flow – negatively affecting indoor air quality.
  • As is standard practice when replacing filters, the filter should be handled by its cardboard frame – without touching the filter media. Care should also be taken not to shake loose anything collected within the filter media – the filter media should be treated as if it contains active microbiological material.
  • It is also important that filter changes do not exceed operating hours or time limits, as microbiological growth can be supported.

> Plastic air filters (indoor air conditioning units)

  • As is standard practice when cleaning filters, the filter should be handled by its frame – without touching the filter media. Care should also be taken not to shake loose anything collected within the filter media – the filter media should be treated as if it contains active microbiological material.
  • Filters should be immediately bagged and taken to a secure area for cleaning.

Air conditioning

Air conditioning systems can operate normally and without adjustment, as the virus is tough and resilient, meaning changes to temperatures or humidity in the environment won’t make much impact. The Irish governments’, Return to work safely protocol (page 21) states that:

7D. HEATING, VENTILATION AIR CONDITIONING (HVAC) Air conditioning is not generally considered as contributing significantly to the spread of COVID-19. Switching off air conditioning is not required to manage the risk of COVID-19. For organisations without air conditioning adequate ventilation is encouraged, for example, by opening windows where feasible etc.


Water systems – Legionnaires disease

Legionnaires disease and its effects bare some relation to COVID-19/SARS-CoV-2, therefore it should be to the forefront of any risk assessment in re-entering a vacant or little used building.

  • Legionnaires disease is caused by legionella bacteria.
  • Similar to the virus, legionella bacteria is inhaled through aerosols – created by water – that are invisible to the eye. The disease can be fatal, especially to people over the age of 40, due to their weaker immune systems.
  • Buildings are a perfect breathing ground for bacteria growth, owing to their heat, ideal temperatures and the presence of little used water pipework.
  • Legionella bacteria favours temperatures of between 25°C to 45°C, with 37°C an ideal temperature. Coincidentally, 37°C is the temperature we like our water at and is also the normal core temperature for the human body.
  • Hot water should be stored at 60°C and delivered to taps at 50°C.
  • Cold water should be stored below 20°C. Whilst temperatures below 20°C don’t kill legionella bacteria – it remains present but doesn’t proliferate. Indeed, legionella bacteria has been found in ice, therefore cold does not kill legionella bacteria.
  • Little used outlets should be flushed on a weekly basis. Both little used outlets and dead legs pose the greatest risks in a system.
  • Flushing of water outlets is one of the most menial tasks but one of the most important. Therefore, staff performing flushing need to be educated through training, to understand why this menial task is so important.

There is often an increase in cases of Legionnaires disease towards the end of the summer, when people return to their homes, having been on holidays. The stagnant water in vacant homes during warm summer months provides a perfect breathing ground for legionella bacteria growth. These conditions are strikingly similar to recent warm temperatures, combined with the recent period of workplace vacancy – providing an ideal breathing ground. Read our further information on Legionnaires disease: causes; signs and symptoms; those at risk; prevention; treatment; testing; risks, national guidelines and your legal obligation.


Safety

Standard procedures apply when removing filters and as a precaution, when inspecting heat recovery systems.

  • Personal protective equipment (PPE) for dusty work – including, gloves, goggles and respiratory protection – must be worn.
  • Disposable air filters should be disposed of in a sealed bag and left, where possible, in a secure storage area for at least 72 hours, before being destroyed.
  • Standard protection safety procedures should be strictly obeyed by maintenance personnel.
  • Read the technical bulletin from the Air Conditioning and Refrigeration European Association (AREA) and their best practice safety advice.

Novel enveloped virus

SARS-CoV-2 is a novel coronavirus, meaning it is new. Studies, evidence and knowledge are constantly evolving and updating, as new information emerges. SARS-CoV-2 is also an enveloped virus, so it does not survive well with the use of soap and alcohol solutions of at least 70%. Please do not forget to keep washing your hands as a protection measure. The information in this guide was compiled with the help of the Federation of European Heating, Ventilation and Air Conditioning Associations’ (REHVA) guidance document and Thermodial’s expert technical knowledge of HVAC systems and building service engineering.


Planned preventative maintenance (PPM)

Thermodial’s approach to heating, ventilation, air conditioning and water systems is a risk-based PPM approach. PPM is a risk averse measure, ensuring uptime of operation critical systems, providing a safe and secure environment for your staff. Talk to Thermodial about preventative maintenance to support your businesses’ critical needs or explore our full PPM capabilities.


Key guidance source materials

Air Conditioning and Refrigeration European Association (AREA) – COVID-19 technical bulletin for advice on special measures

Federation of European Heating, Ventilation and Air Conditioning Associations (REHVA) – COVID-19 guidance document

Health Protection Surveillance Centre (HPSC) – National Guidelines for the Control of Legionellosis in Ireland 2009

Irish government – return to work safely protocol