New World Health Organization guidance on indoor ventilation for COVID-19

Ventilation has long been recognized as central to indoor air quality.  In older Canadian homes there is often ample ‘natural’ ventilation, because cracks in the walls, poor joints, and thin insulation mean a lot of outside air enters the home.  But in offices and newer or retrofitted homes, ventilation rates are usually mechanically controlled—raising the thorny question of how much is needed. For decades there have been concerns with how ventilation is important for smells (such as body odour) and indoor pollutants (such as formaldehyde and ozone).  Now, we are starting to see that the risk of getting COVID-19 is higher in crowded and inadequately ventilated spaces where infected people gather together.  Alternatively, good air circulation can dilute the amount of droplets in air space, reducing the risk of disease transmission.  Indeed, in some cases workers and management have gotten into considerable conflict over whether to reduce risks by opening windows. In one Abbotsford, British Columbia school, teachers began opening the windows only to have them screwed shut by the school, prompting complaints by the union.

The World Health Organization now has new guidance in the Roadmap to improve and ensure good indoor ventilation in the context of COVID-19. It restates the importance of ventilation for human health. It provides simple steps building maintenance staff can take to ensure safer air, with separate guidance for health care settings, residences and non-residential settings (such as workplaces).  For non-health care settings, it provides minimum ventilation rates of 10 litres per second per person, which is higher than many buildings in Canada now operate.  The roadmap should serve as a helpful guide to the many residences and workplaces who now are concerned with ensuring COVID-19 safety procedures.

In the longer term, the WHO’s Roadmap can also help us rethink our indoor air and the role it plays in ensuring we live in a healthy environment. For too long ventilation has been seen as just a problem of smells, and comfort, without recognizing the ways indoor air is often more polluted than outside air. In the last few decades there has been a lot of research pointing to the need for good ventilation to avoid Sick Building Syndrome or carcinogens such as formaldehyde. Ventilation is particularly important as we make our homes and workplaces more energy efficient. This often means making them ‘tighter’ –reducing the amount of uncontrolled air flows that lead to energy loss. This means that energy efficient homes and workplaces cannot rely on ‘natural ventilation’ but need to have good mechanical ventilation systems in place to ensure proper ventilation rates. While Health Canada has emphasized the importance of ventilation for indoor air quality, we still do not have clear standards in the provinces.

It is unlikely that as COVID-19 dies down people will forgot that crowded indoor spaces can spread disease.  The WHO Roadmap is a useful addition to the many voices calling for better, health based ventilation standards, ranging from academic specialists like Andrew Persily  to the Federation of European, Heating, Ventilation and Air Condition Associations.




Page Last Updated: 14/07/2021