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Monitoring & metering


A fresh approach to reducing COVID-19 transmission


Earlier this month, Pfizer and BioNTech announced that their COVID-19 vaccine candidate was 90 per cent effective in protecting people from transmission of the virus. Moderna also announced that their own vaccine candidate showed 95 per cent efficacy, bringing hope that the end of the pandemic may be in sight. But the emergence of two possible vaccines does not mean we can abandon restrictions immediately. With England currently in a second lockdown and the other home nations implementing stricter social distancing measures, many workplaces are searching for ways to operate safely. Could the answer be as simple as opening a window? Fresh air is being touted as the new hand- washing but what is ‘fresh air’ and how do you monitor it? Here, Julian Hayes, CEO of Gas Sensing Solutions, answers these questions


and discusses carbon dioxide (CO2) levels as a proxy indicator for adequate ventilation


is to make sure the space is well ventilated with fresh air. But what exactly is fresh air? Fresh air is typically defined as cool, unpolluted air in natural surroundings. But as there is no agreed parametric definition of what fresh air is, how can you determine if the air indoors is really fresh? Although the World Health Organization


C


(WHO) has not formally confirmed that COVID-19 is spread by airborne transmission, it is probably only a matter of time as other similar viruses such as norovirus and the flu are acknowledged to be spread in this way. In the case of COVID-19, it is believed that ventilation plays an important part in reducing transmission by the dilution and removal of infected particles and droplets. Ventilation is the intentional introduction of


fresh air into a space while the stale air is removed. It is done to maintain the quality of air in that space. According to The American Society of Heating, Refrigerating and Air- Conditioning Engineers (ASHRAE), acceptable


16


OVID-19 is a highly contagious disease and to mitigate the spread of the virus especially indoors, the common refrain


interior air quality is where there are no known harmful contaminants in harmful concentrations. But what constitutes harmful contaminants in harmful concentrations is left to individual States to define, such as the Title 14 California code of regulations, which


stipulates maximum permissible levels of CO2 in a building for example. In the UK, there are guidelines such as the


Building Regulations 2010 for manufacturers, architects and engineers involved with building design and services to assist in the process of reducing poor air quality and ensuring there is enough fresh air ventilation. The Health and Safety at Work etc Act 1974 is the primary piece of legislation covering occupational health and safety. It states that employers have a duty of care to ensure there is a safe and healthy work environment. New and revised workplace exposure limits (WELs) came into force from January 2020 under the auspices of the Health and Safety Executive EH40/2005 guidance containing a updated list of maximum exposure limits and occupational exposure standards for specific gases as required by the Control of Substances


Hazardous to Health (COSHH) Regulations. However, there are currently no regulations


on what constitutes ‘good quality’ indoor air. Although there have been calls on the Government to make measuring and monitoring of indoor air quality a legal requirement in commercial buildings and schools, especially in urban locations, legislation has not yet been forthcoming. The established benchmark test for indoor


air quality is to assess CO2 levels. Ignoring particulate matter, volatile organic compounds


(VOCs) and other contaminants, it is generally


understood that indoor CO2 levels are a good proxy for the amount of pollutant dilution in densely occupied spaces and can therefore be used as a good indicator for fresh air. So how do CO2 levels equate to fresh air?


The amount of carbon dioxide in a building is usually related to how much fresh air is being brought into the building. In general, the higher the concentration of carbon dioxide in the building in comparison to outdoors, the lower the amount of fresh air exchange. The


background level of CO2 outdoors is generally considered to be in the range of 350-450


November 2020 Instrumentation Monthly


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