A new report from the Lancet COVID-19 Commission Task Force on Safe Work, Safe School, and Safe Travel is calling for new non-infectious air delivery rate (NADR) targets to replace the current “bare minimum” standards for ventilation and filtration in buildings in order to promote health and mitigate infection risk.
Since the beginning of COVID-19, many organisations have started focusing on improving indoor air quality also as a means for preventing its spread. The virus, along with many other respiratory pathogens, are often transmitted through inhalation, particularly while indoors or in areas with insufficient filtration and ventilation.
Many building standards, according to the report, are not promoting ventilation and filtration targets that are strong enough to protect against infectious disease transmission.
Results from the study found that enhanced ventilation, filtration, and air disinfection effectively reduce exposure to COVID-19 and other infectious respiratory diseases. Not to mention other positive benefits that include better cognitive function, reduced risk of allergic manifestations and unscheduled asthma visits among children, improvements in subclinical cardiopulmonary health, and quality of life scores.
Amending the current air quality standards
The report reviews three of the most common ventilation metrics – air changes per hour, volumetric flow rate per person, and volumetric rate flow per floor area – and recommends new non-infectious air delivery rate (NADR) targets that are above those of the current standard. These are broken down into seven categories and list pros and cons of each approach.
Approaches include recommendations based on maximum CO2 concentration, equivalent air change rate based for healthcare buildings, floor area, and occupancy. Each approach breaks down its recommended delivery and from which organisation guidance can be followed (WHO, CHC, ASHRAE, etc.)
Recommendations for Reducing Exposure to Airborne Respiratory Infectious Diseases are “feasible and achievable right now with existing and widely available approaches and technologies,” according to the report.
Key findings from the new study
For full details, read the report here.
- Current ASHRAE ventilation rates are too low
- There is a strong agreement between the ACHe approach and the volumetric flow rate per floor area approach
- There is good agreement between the volumetric flow rate per person and the ACHe and volumetric flow rate per floor area approaches
- Volumetric flow rate per person and CO2-based approaches were similar
- Secondary attack rate approaches were in between the occupancy based and ACHe approaches
“The important scientific debates about metrics and targets must continue,” the report says. “However, while there is debate about the ‘best’ metric to use, and there is debate about the specific targets for each, there is no debate that the current targets are too low.”
Now, the Lancet COVID-19 Commission Task Force are calling for change in ventilation and indoor air quality to advance the conversation around health-based ventilation targets for airborne respiratory pathogens.
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