Do you meet the WHO minimum requirements?
‘Roadmap to improve and ensure good indoor ventilation in the context of COVID-19’
Executive Summary:
The risk of getting COVID-19 is higher in crowded and inadequately ventilated spaces where infected people spend long periods of time together in close proximity. These environments are where the virus appears to spread by respiratory droplets or aerosols more efficiently, so taking precautions is even more important. Understanding and controlling building ventilation can improve the quality of the air we breathe and reduce the risk of indoor health concerns including prevent the virus that causes COVID-19 from spreading indoors. At present this is achieved mainly by diluting pollutants originating in the building with clean air, and by providing an airflow rate to change this air at a given rate thus removing the pollutants. Ventilation is the intentional introduction of clean air into a space while the stale air is removed. Ventilation moves outdoor air into a building or a room and distributes it within the building or room. The general purpose of ventilation in buildings is to ensure that air in the building is healthy for breathing. Ventilation, an appropriate operational tool deployed to enhance indoor ventilation, as an environmental and engineering control for the COVID-19 pandemic and beyond. Note: Indoor ventilation is part of a comprehensive package of prevention and control measures that can limit the spread of certain respiratory & viral diseases, including COVID-19. WHO has published numerous recommendations for measures to prevent spread of COVID-19, among which is ensuring good ventilation in indoor settings, including health care facilities, public spaces and residential areas. A well-designed, maintained and operated system can reduce the risk of COVID-19 spread in indoor spaces by diluting the concentration of potentially infectious aerosols through ventilation with outside air and filtration and disinfection of recirculated air. Proper use of natural ventilation can provide the same benefits. The decision whether to use mechanical or natural ventilation should be based on needs, resource availability and the cost of systems to provide the best control to counteract the risks. SARS-CoV-2 transmission is particularly effective in crowded, confined indoor spaces where there is poor or no ventilation. Therefore, ensuring adequate ventilation may reduce the risk of COVID-19 infection. This roadmap aims to define the key questions users should consider to assess indoor ventilation and the major steps needed to reach recommended ventilation levels or simply improve indoor air quality (IAQ) in order to reduce the risk of spread of COVID-19. It also includes recommendations on how to assess and measure the different parameters, specifically in health care, non-residential and residential settings. It is meant to be a technical document helping users to analyse building HVAC systems in order to implement, if required, the different strategies proposed to improve HVAC’s ability to mitigate and reduce the risk of COVID-19 transmission. Question posed: Does the ventilation rate meet WHO minimum requirements? If the answer retuned is NO then; Healthcare Settings including quarantine facilities: Natural Ventilation Strategy:- Assess the opening locations and opening surfaces considering potential new openings (add/modify window or door dimensions).
- Consider enabling cross ventilation rather than single-sided ventilation. Note: Cross ventilation should not be implemented in these specific cases: • within a room or ward for COVID-19 suspected cases where AGP may take place and when the exhaust air is not properly managed; • when the airflow is moving from a less clean to a clean area.
- If the system does not allow increasing ventilation to the recommended minimum per person requirement, consider reducing the maximum room occupancy to meet the L/s/patient standard.
-
- If no other (short-term) strategy can be adopted, consider using a stand-alone air cleaner with HEPA filters. Pay attention to the airflow direction (from clean to less clean areas) when positioning. The air cleaner should be positioned in the areas used by people and close to people, to provide the maximum possible treatment of the source(s) of infection. Stand-alone air cleaners should be operated continuously and air cleaner capacity should at least cover the gap between the minimum requirement and the measured ventilation rate – compare the device clean air delivery rate (CADR) (m³/hr) with the room ventilation rate. Note: Consider that stand-alone air cleaners do not replace ventilation in any circumstance.
- In consultation with a HVAC professional assess the opportunity to increase the ventilation rate according to system capabilities. Disable demand-control ventilation controls that reduce air supply based on temperature or occupancy (CO2 concentration).
- If the ventilation rate cannot be increased mechanically, consider maximizing ventilation by using natural ventilation through opening windows.
- If the system does not allow increasing the ventilation to the recommended minimum per person requirement, consider reducing the maximum room occupancy to meet the L/s/patient standard.
- If no other (short-term) strategy can be adopted, consider using a standalone air cleaner with HEPA filter. Pay attention to the airflow direction (from clean to less clean areas) when positioning. The air cleaner should be positioned in the areas used by people and close to people, to provide the maximum possible treatment of the source(s) of infection. Stand-alone air cleaners should be operated continuously. Air cleaner capacity should at least cover the gap between the minimum requirement and the measured ventilation rate – compare the device clean air delivery rate (CADR) (m³/hr) with the room ventilation rate. Note: Consider that filtered recirculated air does not replace ventilation in any circumstance
- The use of a pedestal fan placed close to an open window could enable ventilation.
- Installation of air extractors or whirlybirds; building works to improve stack effect of other natural ventilation strategies.
- If no other strategy can be adopted, consider using a stand-alone air cleaner with MERV 14 / ISO ePM1 70-80% filter. The air cleaner should be positioned in the areas used by people and close to people.
- In consultation with a HVAC professional, assess the opportunity to increase the ventilation rate according to system capabilities. Disable demand-control ventilation controls that reduce air supply based on temperature or occupancy.
- If the ventilation rate cannot be increased mechanically, consider maximizing ventilation by using natural ventilation through opening windows.
- If the system does not allow increasing the ventilation up to the recommended minimum per person requirement, consider reducing the maximum room occupancy to meet the L/s/person standard.
- If no other strategy can be adopted, consider using a standalone air cleaner with MERV 14 / ISO ePM1 70-80% filter. The air cleaner should be positioned in the areas used by people and close to people. Stand-alone air cleaners should be operated continuously.
- Assess the opening location and opening surface considering potential new openings (add modify window or door dimensions).
- If available, exhaust fans in bathrooms, toilets and kitchen should be operated continuously within the isolation area.
- Ensure cross ventilation, if not yet present, instead of single-sided ventilation. Keep doors open to allow air movement. Note: Consider step below prior to implementing cross ventilation.
- Window-installable products are available to provide exhaust ventilation.
- The use of a pedestal fan placed close to an open window could enable ventilation. A fan facing towards the window (i.e. facing outside) serves to pull the room and exhaust air to the outside.
- If no other strategy can be adopted, consider using a stand-alone air cleaner with MERV 14 / ISO ePM1 70-80% filter. The air cleaner should be positioned in the areas used by people and close to people, to provide the maximum possible treatment of the source(s) of infection.
- If the ventilation rate cannot be increased mechanically, consider maximizing ventilation by using natural ventilation through opening windows (see natural ventilation section for more strategies).
- If there is a forced air system that would mix the air between the household and the isolation space, return grilles or supply grilles within the isolation area should be sealed.
- In consultation with a HVAC professional, assess the opportunity to increase the ventilation rate according to system capabilities. Disable demand-control ventilation controls that reduce air supply based on temperature or occupancy.
- If no other strategy can be adopted, consider using a stand-alone air cleaner with MERV 14 / ISO ePM1 70-80% filter. The air cleaner should be positioned in areas used by people and close to people, to provide the maximum possible treatment of the source(s) of infection.