Are your ventilation strategies fit for purpose to protect against coronavirus? Daikin Applied explores how FMs can reduce the risk of COVID-19 transmission inside buildings.

The importance of maintaining heating, ventilation and air conditioning (HVAC) systems to protect human health and wellbeing has been brought sharply into focus this year. Especially now that more workers are returning to their offices and children are heading back to the classroom.

The World Health Organisation (WHO) has acknowledged threat of airborne transmission of the Coronavirus following widespread evidence that showed tiny particles containing the virus could become suspended in the air for some hours.

These findings have important implications. It is now clear that hand washing and face masks alone cannot prevent the spread of Coronavirus in indoor environments with poor ventilation, and that air conditioning systems could play an important role to reduce transmission rates.

However, there were certain adjustments facilities managers could make that would further reduce the risk of transmission. Follow these useful tips on how to run building services during COVID-19 pandemic:

Do 1. Increase air change rates. This will dilute the airborne viral load.

a. Maximise the amount of air being brought into the occupied spaces.

b. Systems that recirculate the air should be switched to ‘full fresh air’.

c. Recirculation dampers can usually be switched off manually or by using electronic controls.

d. Return air from air handling units should be minimised and ‘purging’ carried out.

e. Run systems for longer and at higher speeds than normal.

f. Start running your systems at higher speeds two hours before occupation.

g. Keep systems running at lower speeds overnight and at weekends to purge the building.

h. Exhaust ventilation systems of toilets should be on 24/7.

2. Use more window airing (when mechanical ventilation is not present). It is not advised to rely on window airing alone (see points b and c).

a. It is important to keep windows open in different spaces in order to achieve cross flows through the building.

b. However, it is not a good idea to rely on simply opening windows. If there is little or no wind, this will have little effect, especially if the outside temperature is lower than the inside temperate,


which will cause the air to flow out rather than in, resulting in even less air supply to the occupants.

c. Outside air, if polluted, may create other risks to health. This is especially important to consider in urban areas. Air purification technologies could be used in certain circumstances.

Take into consideration whether new partition walls have been erected, or desks moved, as social distancing measures – this will change the way air moves around in the space and will affect whether ventilation is still fit for purpose.

Regularly check, clean and replace filters (maintenance staff should wear full PPE to carry out this task). Clogged filters are not a contamination source in this context, but they may reduce supply airflow.

To consider 1. Air purifiers can be useful in specific situations.

a. To be effective, air purifiers need to have at least HEPA filter efficiency.

b. Devices that use electrostatic filtration principles (not the same as room ionisers) often work quite well.

2. Introduce HVAC and office interior fogging to your regular maintenance routine. (Fogging is a method of sterilisation, to kill viruses, bacteria and micro- organisms including legionella and fungicides).

3. Introduce duct cleaning to your regular maintenance routine (to ensure they meet cleanliness requirements BS EN 15780 (Ventilation for Buildings. Ductwork. Cleanliness of Ventilation Systems).

a. Duct cleaning removes unwanted substances such as debris and dust from ductwork and sanitising prevents mould building up in the system.

b. Duct and air sampling ensures good quality air is circulated through the HVAC units.

c. Pay particular attention to ensuring grilles on extract vents within toilets are clear.

d. Establish a regular inspection process. Every 12 – 24 months is advised.

4. Humidifiers should be checked to maintain relative humidity levels are in line with recommendations for minimising airborne viruses.

Do Not 1. Do not use recirculated air

2. Increase humidification or indoor air temperatures as these have no practical effect in killing the coronavirus.

It is more important now than ever to ensure that mechanical ventilation and air conditioning systems are working as intended and are well maintained.

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