Specialists in infectious diseases around the world are asking the World Health Organization (WHO) to address the interior air quality of public buildings in order to improve the health and well-being of occupants.
While the WHO currently sets guidance for indoor air quality on issues such as pollution and mould, it offers no recommendations for a minimum humidity level in public buildings.
“I am calling on the World Health Organization to review the scientific evidence on humidity and health and recommend a minimum lower limit of indoor humidity in public buildings to reduce respiratory infections,” says petition co-author Dr. Stephanie Taylor, an infection control consultant at Harvard Medical School. “There is now overwhelming scientific evidence that a mid-range air humidity has significant benefits for human health.”
The petition authors believe that 40 to 60 per cent relative humidity (RH) in public buildings like hospitals, schools and offices should be maintained throughout the year.
They outline three key benefits: performance improvements in the respiratory immune system; a reduced ability for virus droplets to remain airborne; and the enhanced possibility for physiochemical reactions to occur that deactivate the virus.
Maintaining a 40 to 60 per cent humidity level in buildings would also reduce many other airborne respiratory viruses, the petition authors say. The result would be thousands of lives saved each year and a less burdened global health care system.
Air circulation is important too. Erin Bromage, Ph.D., and associate professor of biology at the University of Massachusetts Dartmouth, describes a specific case where air movement within the confined space of a restaurant spread COVID-19 to several patrons via one single carrier.
“The infected person sat at a table and had dinner with nine friends. Dinner took about one to 1.5 hours. During this meal, the asymptomatic carrier released low-levels of virus into the air from their breathing. Airflow (from the restaurant’s various airflow vents) was from right to left. Approximately 50 per cent of the people at the infected person’s table became sick over the next seven days. Seventy-five per cent of the people on the adjacent downwind table became infected. And even two of the seven people on the upwind table were infected (believed to happen by turbulent airflow).”
Virus spread is also possible through simple speech. Researchers at the National Institute of Diabetes and Digestive and Kidney Diseases and the University of Pennsylvania say that small respiratory droplets from speaking linger in the air for at least eight minutes and potentially much longer. Loud speech produces even more droplets.
Going further, Michael Driedger, the co-founder and CEO of property automation system developer Operto Guest Technologies, says improved overall indoor air quality is essential in all aspects of today’s world.
“The average person spends 90 per cent of their time indoors. In many places, the outdoor air is bad enough that it becomes difficult to breathe. Then, being inside a building can become the safest place, where building level HVAC systems containing various filters remove contaminants from the air,” he says.
Driedger points out while carbon monoxide poisoning, chemical or air pollution-induced asthma and acute lower respiratory infections kill thousands of people each year, they can be detected using sensors and mitigated through building design.
Addressing residential and hospitality buildings specifically, Driedger cites a 2015 study of college students’ sleeping patterns. Those who slept with windows open to vent CO2 slept significantly better than those with higher CO2 levels and performed better on next-day cognitive tests.
COVID-19 is providing impetus for scientists to encourage the WHO to use its international leadership position.
“The containment of the COVID-19 pandemic requires a worldwide lockdown,” says petition co-author Adriano Aguzzi, professor and director of the Institute of Neuropathology at the University of Zurich. “While this is extremely effective in reducing outdoor contagion, it does not prevent indoor transmission of SARS-CoV-2.”
Joining his peers, Aguzzi calls on the WHO to “take action to mitigate seasonal illness and improve the health of building occupants across the world.”
It is indeed high time for HVAC professionals to take a closer look at the system that they advocate. Existing HVAC is passed especially with the need to contain the spread of diseases. Conditioning air in an enclosed space needs a new thinking. I would like to propose a system of open space air conditioning with controlled ventilation.