Increasing Ventilation to Reduce the Risks

Increasing Ventilation to Reduce the Risks

By Ruth MacEachern

Product Manager

Mark Isles, Sales Director – Build at EnviroVent looks at how ventilation is being addressed in commercial buildings to make workplaces safer and healthier.

“With the government encouraging greater numbers of people to return to work in offices, gyms, dentists and schools the onus is on employers and building owners to ensure they are Covid-19 safe, which includes having effective ventilation in place to minimise the risks of virus transmission.   

HSE guidance has always required employers to ensure an adequate supply of fresh air is available in the workplace – and this has not changed.   However, now with the risk of Coronavirus, HSE guidance is focused on reducing the risk of spreading the virus by improving general ventilation, preferably through fresh air or mechanical ventilation systems. This is backed by organisations including CIBSE, ASHRAE, REHVA and BESA, which are advising that workplaces boost ventilation so indoor air is sufficiently diluted to eliminate the potential for airborne viral transmission

The CIBSE Covid-19 Ventilation Guidance offers specific guidelines for specifiers and building owners focusing on what can be done to reduce the risk of viral infection transmission indoors.  

The case for good ventilation

Evidence from the European Centre for Disease Prevention and Control (ECDPC) states that poor ventilation in confined indoor spaces is associated with the increased transmission of respiratory infections, such as Covid-19.  Studies of 318 outbreaks of Covid-19 demonstrated that transmission in all but one case had occurred in indoor spaces. 

SARS-CoV2, the virus which causes Covid-19, can be spread via very small particles, which are released by an infected person when they cough, sneeze, talk or breathe.  Larger droplets will fall due to gravity and if the 2m distancing is observed, risks should be lower, however smaller particles can remain airborne for several hours.

The CIBSE guidance recommends that building owners increase the ventilation rate to dilute airborne contamination in order to reduce the risk of exposure for building users. This should be carried out in conjunction with other government advice including working from home, social distancing, hand washing and wearing face coverings. 

Key actions from the CIBSE guidance include:

• Understand the ventilation system
• Run ventilation at higher-volume flowrate
• Avoid recirculation/transfer of air from one room to another unless this is the only way of providing adequately high ventilation to all occupied rooms
• Recirculation of air within a single room where this is complemented by an outdoor air supply is acceptable
• If applicable, thermal wheels should be switched off, but the pressure difference between supply and extract will need to be maintained to minimise any leakage flow from the extract to supply side

This ventilation guidance is under constant review and may be updated during the autumn and winter seasons.

To keep risks as low as possible, the guidance recommends that the number of air changes should be as high as reasonably possible. This will ensure dilution and removal of airborne pathogens, exhausting them to the outside air and reducing the chance that they can become deposited on surfaces or inhaled by room users. This is particularly important in poorly ventilated areas.

In rooms and zones where there is no direct supply of outside air then the guidance states that consideration should be given to prohibiting access to these spaces by building users, especially where it is likely that they would be occupying such a space for a considerable length of time (longer than 30 minutes). This may include basement rooms or storage areas which rely on infiltration of air from other spaces.

Assessing carbon dioxide levels

According to the CIBSE Ventilation Guidance, non-dispersive infrared (NDIR) CO2 sensors are useful devices to help assess whether adequate ventilation is being provided to an occupied zone. Indoor ventilation dilutes exhaled CO2 from sedentary occupants and so the carbon dioxide concentration in a space is often used to determine ventilation rates.  For demand-control systems, the CIBSE guidance advises CO2 set points should be set to no less than 400ppm to meet the basic air change provision.  It is also recognised that when sensors detect CO2 concentration of 1000ppm (parts per million) this will translate to an equivalent outdoor air supply of 8-10l/s/person within that application.

It is recognized that some areas of a building may not have natural or mechanical ventilation.  For these, HSE guidance states that building owners and occupiers need to improve the circulation of outside air and prevent pockets of stagnant air appearing in occupied spaces. They suggest this can be done by using ceiling fans or desk fans, provided good ventilation is maintained.

An effective option is EnviroVent’s AirSens range of intelligent indoor air quality sensors, which are being widely adopted throughout offices and other commercial premises, such as small shops, nurseries, schools and health centres.  These can be connected to many of EnviroVent’s ventilation products and systems.

With an AirSens AIR- CO2 indoor air quality sensor and SILENT MV inline fan solution, adequate air changes will be delivered within an application to mitigate risks posed by COVID-19 transmission via droplets or small airborne aerosol particles.

Increase ventilation, reduce risks

Industry experts have concluded that HVAC systems may play an important role in decreasing the transmission of infection in indoor spaces by increasing the rate of air change, which reduces the recirculation of air and increases the use of fresh outdoor air.

COVID-19 has highlighted the need for good ventilation in buildings – something that has already been recognised for decades by many specifiers. Prior to the arrival of Covid-19, there was already compelling evidence presented by the Royal college of Paediatrics and Child Health (RCPCH) and the Royal College of Physicians which demonstrated that respiratory problems among children may be exacerbated by indoor air pollution in homes, schools and nurseries.

Many experts have noted that a badly ventilated building is an ill building and ‘sick building syndrome’ has been widely publicised in recent times. Poorly ventilated buildings are those which will inevitably lead to ill occupants and never has this been truer than today.  Employees deserve the right to be effectively protected in the workplace and it’s here that mechanical ventilation systems can really make a difference.”

For more information on improving the air quality in the  workplace, visit the website www.envirovent.com or to find out more information about EnviroVent’s products call 0345 27 27 810.