WHAT’S the problem? With cold weather and increases in seasonal indoor activities, ensuring adequate and effective indoor ventilation remains critically important, along with other virus control measures. Yet it is often neglected with good information lacking and best practice missing.

The Scottish Health Secretary told BBC Scotland on December 5 that when people meet indoors over the Christmas period, they should “try to ensure adequate ventilation”. What is “adequate” and how exactly customers and workers and householders can try to “ensure” ventilation remains unclear. Only Government can “ensure” the standards are applied across the country – not individual workers, residents, or customers.

Walking around large and small stores, shops, cafes, pubs, offices, and workplaces in Scotland at the moment, it is sometimes quickly evident which places appear to be well ventilated and which are not. However, it is not possible to judge accurately without additional information, detailed risk assessments and monitoring and inspections, and these are often missing. Even in some schools and other workplaces, reports are still emerging of poor ventilation risk assessments and limited CO2 monitoring to check ventilation performance.

Further complications have emerged at times with mixed or complacent messages from some Scottish Government expert advisers who have downplayed the Covid threat up to Christmas. Other commentators suggested incorrectly that vaccination alone will protect public health this year. How the public interprets these messages when mixing indoors in places with inadequate ventilation must be a major concern. The Scottish Government websites do provide information on Covid, fresh air and ventilation. These link to other important mitigation measures. The importance of requiring specific ventilation risk assessments is highlighted and more detailed information is provided on particular sectors. However, much of this material is limited in scope, very basic and difficult to apply. Information on household ventilation is also very poor in comparison with several other countries.

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Why is ventilation still a problem? SARS-CoV-2 transmission by aerosols has long been recognised but either all too seldom acted upon or frequently ignored by UK regulators. As Dr Stephanie Dancer and others observed, in the context of global long-term neglect of investment and planning “healthcare, homes, schools, and workplaces should have been encouraged to improve ventilation at the very beginning of the pandemic, but tardy recognition of the airborne route by leading authorities in 2020 stalled any progress that could have been made at that stage”. In Scotland, indoor ventilation generally has been neglected for decades. Now the UK Health and Safety Executive (HSE) maintains airborne SARS-CoV-2 is not a “serious” but only a “significant” risk to workers so no meaningful enforcement action has taken place. HSE remains beyond the control of the Scottish Government.

What should householders and workers do about ventilation? Various professional, non-governmental organisations and trade unions produce useful information on ventilation measures necessary to protect occupants from Covid. The Hazards Campaign, for example, frequently provides detailed but user-friendly practical information on ventilation standards and controls that should be applied. This is often better than many UK Government publications. Much depends on thorough employer and landlord risk assessments being done that take account of building design and structure, relative humidity, room purging, usage, numbers of occupants, and other factors.

Carbon dioxide (CO2) is used as a good ventilation proxy measure. Suitably sited, reasonably priced and accurate indoor monitors taking account of space and occupancy numbers can measure CO2. Indoor air CO2 readings of 600 to 800 parts per million (ppm) indicate good room ventilation. HSE agrees with this figure. Higher levels would be a cause for concern, but HSE considers 1500ppm should trigger employer action on poor ventilation, and that is not precautionary.

HSE regulatory guidance indicates ventilation air flows should not normally fall below five to eight litres per person per second. The Chartered Institution of Building Services Engineers recommends 10 litres of air per person per second in classrooms and offices. The World Health Organization also recommends six air changes per hour and other experts recommend nine or 10 air changes. What is wanted for good ventilation is an air flow of at least 10 litres per person per second with a minimum of six air changes an hour. Covid variants may complicate ventilation risk assessments further because Delta generates more aerosols than Alpha, making good ventilation more important. The Omicron variant currently remains an unknown quantity, but could generate even more aerosols.

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SAGE in October 2021 advocated “scores on doors” to rate room ventilation along with some form of certification. This approach could be applied to workplace, public and hospitality settings and better inform customers, visitors, and workers about building ventilation levels. Scores would cover natural and mechanical ventilation available indoors, monitoring carbon dioxide levels, window and door openings, presence, or absence of high efficiency particulate air filters (HEPA), reduced room occupancy numbers, social distancing capacity, and time spent in indoor spaces.

The US government’s Centre for Disease Control (CDC) provides practical and clear information on improving workplace building ventilation. It has additionally developed an interactive tool to help people improve home ventilation. This includes information on safe door and window opening, fan use and location including in kitchens and bathrooms, air filters with central heating, ventilation, air conditioning systems, and HEPA air filters. CDC also included information and advice on visitor numbers to homes, time to be spent inside, and room size effects.

Scotland has undoubtedly done less badly than England in dealing with certain aspects of ventilation. Nevertheless, the Scottish Government still often falls short on the provision of clear, easily accessible, and sufficiently detailed information on workplaces, schools and colleges, the hospitality sector, and public buildings. The best ventilation standards and controls available are not always adopted and implemented. Monitoring and inspection of premises can be deficient. More action is needed to reassure the public that “adequate” ventilation standards exist and are used across the country.