According to a paper prepared by the Environmental and Modelling group (EMG) and published by the Scientific Advisory Group on 23 October 2020 titled ‘The Role of Ventilation in Controlling SARS-CoV-2 Transmission’(which can be downloaded here) it is stated that “Ventilation is an important factor in mitigating against the risk of far-field (>2m) aerosol transmission”
Amongst the recommended actions it is recommended that ‘Ventilation should be integral to the COVID-19 risk mitigation strategy for all multi occupant public buildings and workplaces.’
The basic principle is that increasing the amount of fresh air in a workplace, acts to dilute any virus which may be present, thus decreasing the viral load which any occupants are exposed to. This results in a reduced risk of catching the virus, and a reduced severity of infection if you do catch it.
The amount of fresh air required is directly dependant on the amount of people occupying the space.
Prior to the emergence of COVID-19 the recommended fresh air rate in offices specified by Building Regulations was 10 litres per second for each occupant in the space, and we believe this still represents an appropriate amount for conditions where the virus is not prevalent.
At the height of the pandemic, scientific review suggested that fresh air rates should be increased even further to dilute viral load, and a doubling of fresh air rate and 20 litres per second per person was suggested for use whilst high levels of virus were present.
Recommendations For Reducing Virus Transmission
COVID-19 has provided the world with a real wake up call with regards to the possibility of future dangerous and disruptive viral developments, and we need to take these lessons into account when designing our building services, in order to provide safe offices and workplaces for the future.
Employers have a duty of care to ensure, as far as reasonably practical, the health of their employees at work. Providing adequate ventilation is an important component of a healthy work environment, and is prescribed by law in regulation 6 of the Workplace (Health, Safety and Welfare) Regulations 1992 (HMSO, 1992).
As a company we are suggesting that all our clients should consider ensuring that all occupied workplaces are provided with a minimum of 10 litres per second per person – and that where clients wish to continue working during prevalence of a virus – they should consider the implementation of an uprated system which should be capable of being boosted to 20 litres per second per person under conditions where viruses are prevalent – this will mean that the workplace can be operated efficiently at times of no virus and with greater safety when viruses are present.
In the UK, the vast majority of small commercial air conditioned offices have no provision for the introduction of additional fresh air, as they inevitably utilise recirculating split type air conditioning units to both heat and cool the spaces and windows need to be kept closed to maintain security, noise levels and thermal comfort – so most clients will need additional ducted fresh air systems in order to comply with the above requirement.
We believe that the most efficient and effective equipment to add to your existing air conditioning to provide the recommended amount of fresh air is the Mitsubishi Lossnay system which both extracts stale air from the space and brings in fresh air with an efficient heat exchanger which minimises the requirement for additional heating and cooling.
Feel free to call us on 01706 367 500 to discuss your potential project – we would be happy to provide a no obligation written quotation.
Frequently asked questions :
- What is the role of CO2 sensors ? : Carbon dioxide sensors are a useful tool to measure the amount of fresh air in the space as each occupant breathes out CO2. In Europe some counties have set maximum CO2 levels as a way of ensuring compliance with good fresh air levels. It is generally acknowledged that 10 litres per second per person of fresh air will result in CO2 levels of 800-1000 PPM although this will depend on activity type within the space, as well as individual metabolism of persons in the space. We believe the most effective way of implementing good ventilation is to ventilate in accordance with maximum occupancy levels. If clients wish to validate this periodically by measuring actual CO2 levels then this can also be accommodated.
- Should I turn my air conditioning off to prevent the spread of COVID ? : During the early part of the pandemic it was thought that COVID was spread primarily by droplets projected from the mouth of an infected person when they cough or sneeze, and that the draught from an air conditioning unit could carry these droplets further, thus increasing risk of infection. This has now been proven to be incorrect. The virus particles remain suspended in mid air for several hours and behave almost like a gas or smoke, naturally dissipating throughout the space even with air conditioning switched off. The only way to reduce the spread of virus is to dilute the viral load with increased fresh air. It can be argued that for clients who have adequate fresh air levels, operating the air conditioning system spreads the fresh air throughout the space resulting in more even levels of viral load.
- Will my air conditioning be able to cope with these increased fresh air quantities within the space ? : The Lossnay system recovers heat from the exhaust air stream thus minimising the effect of bringing in fresh air. As long as clients existing air conditioning systems are adequately sized then comfort levels should be able to be maintained. However you should expect your air conditioning systems to have to operate that bit harder to maintain temperature, and under extreme ambient temperatures it is possible that internal temperature may fluctuate by a couple of degrees. If this is a problem then supplementary air conditioning should be considered.