How ‘fresh’ is your air?

The debate over the air quality inside buildings has taken on new urgency as more buildings re-open after the lockdown making it crucial that facilities managers get their ventilation strategies right, says James Henley*.

The issue of air quality in re-opening buildings has received widespread media coverage including a feature on BBC News. Reports advised workers to refuse to enter “stuffy” offices because these could pose a risk of a second spike in Covid-19 infections.

Opening windows was the main tactic recommended by national media, but anyone who occupies a building in an urban environment should have their doubts about that.

If there is little or no wind, the air will not naturally flow into a building from outside particularly if the temperature outside is colder than inside – so air movement cannot be guaranteed. Another problem – potentially much more serious – is the risk of increasing the amount of polluted air entering the building.

The World Health Organisation (WHO) also remains concerned that outdoor air continues to be frequently used as supply air for ventilation systems despite heavy contamination by particulates and other outdoor pollutants. It has called for much more effective use of air filters and room air purifiers in homes, businesses and buildings with particularly vulnerable occupants like care homes and hospitals.

Balancing one health risk against another

Indoor air is often five times more polluted than outdoor air due to the increased concentration in a confined space and the mixture and combination of pollutants from both internal and external sources.  Therefore, the need to increase air change rates to reduce the virus transmission rate must be balanced with the threat posed by outdoor pollution.

You can’t simply offset one health risk by increasing another.

Therefore, mechanical ventilation systems should be seen as the first line of defence. And these must be correctly set to maximise the amount of air being brought into the occupied spaces and should be regularly maintained to reduce the intake of external contaminants.

It is a good idea to keep systems running for longer and at higher speeds than normal – starting two hours before occupation and kept running at lower speeds overnight and at weekends to purge the building.

Systems that recirculate the air should be switched to ‘full fresh air’ mode to minimise the risk of contaminated air re-entering the building during the ongoing pandemic. Recirculation dampers can usually be switched off manually or by using electronic controls. Return air from air handling units should be minimised and ‘purging’ carried out to avoid air moving from the extract side to the supply side of these units.

Filters should be regularly checked and cleaned or replaced and maintenance staff should wear appropriate PPE when carrying out this work. This will mean the system can continue to refresh the air while reducing the threat from outdoor pollutants.

While physical intervention like this remains important, there is also an increased amount we can do to keep building occupants safe using remote monitoring technology.  Building engineers can now easily assess the condition of equipment from a remote location – making it possible to repair and maintain systems even when physical access is severely restricted.

Even before the crisis, the global market for ‘smart building systems’ was predicted to grow to more than £30bn by 2022. That meant this sector was outstripping any other part of construction by far.

The pattern of economic recovery remains uncertain, but there is clearly a strong case for further investment in this kind of technology; not least because it will allow the building services industry to maintain operating quality and productivity whatever restrictions we face in the future.

Continuous monitoring also allows facilities managers to spot early warnings with important cooling systems, for example. If a chiller or air handling system is not achieving its design capacity or efficiency, it may be because the refrigerant charge is low or operating pressures have become too high – in any case, they will be alerted before the problem becomes serious.

Avoiding costly breakdowns

This allows potential breakdowns to be avoided and any drop in performance to be addressed before it starts to affect the building and its occupants.

Repair work and energy usage account for around 85% of the total lifetime cost of an air handling unit – so it is important to get these things right. Buildings are also responsible for around 40% of global energy consumption with HVAC systems the biggest contributor.

The availability of digital technologies means building services designers are gaining more control over how a building will perform in use and, therefore, how much energy it will consume – as well as how safe and healthy it is for occupants.

*James Henley is Product Development Manager at Daikin Applied UK.