In order to ensure a safe and healthy working environment, spaces will need to undergo certain procedures before employees return to work. The government has released an official document prepared by the Department for Business, Energy and Industrial Strategy (BEIS), with guidelines for working safely during COVID-19 in offices and contact centres. An essential part of this practical framework is outlined in section 5.1, entitled ‘Before Re-opening’, which states that ventilation systems must be reviewed to ascertain whether they need to be serviced or adjusted.
The COVID-19 pandemic has prompted concerns over the way in which many heating, ventilation, and air conditioning (HVAC) systems currently operate. The Federation of European Heating, Ventilation and Air Conditioning Associations (REHVA), have also released a guidance document calling for engineers to stop recirculating air in buildings in areas with an outbreak of the virus. This is due to the fact that small particles (up to 5 micrometres), generated by coughing and sneezing, can stay airborne for many hours and travel long distances. A COVID-19 particle is only 0.8 to 0.16 micrometres in diameter, so there could conceivably be multiple virus particles in a 5 micrometre droplet that is floating in the air.
Turning off systems that use local recirculation can therefore avoid resuspension of virus particles within your space, reducing the risk of transmission. As many of these systems are essential for temperature control, it is important to consult an HVAC engineer to see if it is practical to implement this strategy. Not only can the virus be transmitted directly by airborne viral aerosols, but there is also the risk of these aerosols settling on surfaces. A study from The New England Journal of Medicine found that COVID-19 was still detectable on copper for up to 4 hours, on cardboard for up to 24 hours, and on plastic and steel for up to 72 hours. It is therefore paramount to limit surface contamination so that occupant safety is optimised.
Future buildings will undoubtedly need considerably improved ventilation systems to tackle the issues of cross-contamination and air distribution. Risk assessments will need to be updated to consider the risk of spreading infection through air-recirculation. To make current buildings safer, diluting internal air by increasing ventilation is a vital step to reduce the risk of airborne transmission. It is important to supply as much outside air as is reasonably possible, in order to increase the amount of fresh air supplied per person.
The risk posed by the air in a building can be lessened by maintaining a sufficient space between occupants, and it is likely that social-distancing regulations will ensure that this is the case. Where possible, opening windows is another effective way of boosting air exchange rates, although this is not possible in many modern spaces and the quality of air that will be introduced via the open windows needs to be considered.
As well as increasing ventilation, temperature and humidity have a role to play in the survival rate of viruses, by providing more favourable environments for them to survive and spread. Low humidity can cause mucous membranes to dry out, compromising our body’s natural defence. Research indicates that maintaining your space’s relative humidity between 40% and 60% can decrease the bio-burden of infectious particles in your space and decrease the infectivity of many viruses in the air. HVAC systems need to be adjusted accordingly to ensure that temperature and humidity remain at an optimal level.
Building owners are encouraged to improve the efficiency of the filters serving their HVAC systems. The building readiness guidelines released by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) state that recirculation filter efficiency should be at least MERV 13 and preferably MERV 14 or better to help mitigate the transmission of infectious aerosols. Whilst these filters are better at removing particles with a diameter between 0.3 and 1 micrometres, they also require greater air pressures to drive air through the filter. It is therefore essential to ensure that the capacity of the HVAC system is sufficient to accommodate the better filters without adversely affecting the way in which the system functions. Upgrading filters on outdoor air systems may have little practical effect on reducing transmission, although this study suggests that the virus can be present on air pollution particles.
It is clear that a wide range of factors must be carefully considered before employees return to the workplace. At AirRated, we can support you by providing a comprehensive review of your HVAC system. We will then provide recommendations for adjustments to optimise the safety of your space, and to mitigate the potential transmission of COVID-19.
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