Ventilation guidelines not included in Sask. back-to-school plan

Some Saskatchewan experts say good ventilation practice and systems could help reduce potential airborne exposure to the novel coronavirus in schools. 

Guidelines for schools released by the federal government on Friday suggest ensuring ventilation systems work properly, increasing air exchanges by adjusting their systems, opening windows and moving outdoors where possible. 

The provincial government's Safe Schools Plan, released on Aug. 4, does not include recommendations or guidelines for ventilation.

Dr. Anne Huang, Saskatchewan's former deputy medical health officer and current public health physician, said the plan should address ventilation. 

"There has been a lot more attention and awareness on the potential of the novel coronavirus being transmitted through the inhalation route, meaning that infectious droplets or micro droplets or aerosols that could remain suspended in the air for minutes to hours," said Huang. 

"That route of transmission hasn't been expressly addressed in this document."

Huang said poor ventilation could potentially increase the amount of time that staff and students are exposed to the virus if it is in the air, particularly if they are not wearing masks. 

The Ministry of Education said in a written statement that guidelines or recommendations on ventilation would be developed in consultation with the Ministry of Health and the office of the chief medical health officer.

"The Ministry of Education will work with school divisions should there be any concerns over ventilation systems in schools as it concerns public health."

Unclear data

Some studies have shown that the virus can travel through the air, but the World Health Organization says more research is "urgently" needed to assess airborne transmission. 

According to the WHO website, aerosol transmission cannot be ruled out when looking at reported outbreaks of COVID-19 in closed settings, for example at restaurants or places of worship, where people may be talking, shouting or singing.

This is particularly the case "in these indoor locations where there are crowded and inadequately ventilated spaces where infected persons spend long periods of time with others," the WHO website states.

Dr. Joseph Blondeau, head of clinical microbiology at Saskatoon's Royal University Hospital and the University of Saskatchewan, said it is theoretically possibile that ventilation systems or air conditioning could disseminate the virus.

"But the data is not very clear," said Blondeau. 

"Most of the studies that have been done have been unable to rule out the possibility that it was person-to-person spread."

The federal COVID-19 guidance for schools points out in a footnote that "increasing ventilation may help to reduce transmission, though the exact parameters are unknown."

Hand washing, physical distancing, cleaning surfaces and proper coughing etiquette are probably more important when it comes to reducing the spread of the virus, Blondeau said. 

HVAC systems can minimize exposure to airborne particles

Humans who are infected with influenza can generate about 2,000 infectious aerosol droplets per hour, according to Carey Simonson, professor of mechanical engineering at the University of Saskatchewan.

Aerosols are very small droplets which can be transported through the air for a long distance as they float with the natural currents or through an air duct, Simonson said. 

"If I am in one room and I have a ventilation system … that takes air from my room and air from another room and mixes it and then sends it back into each respective room, certainly some of those aerosol viruses will make that trip," said Simonson.

"The question is how many, and how many are needed to actually infect someone, and how long would they need to be exposed to be infected."

He recommends HVAC systems — heating, ventilation, air condition systems — as a tool to minimize the exposure to airborne particles which could contain viruses.

Systems that bring fresh air into a building and exhaust air from a room directly outdoors would be the safest, according to Simonson.

Different ventilation systems

Simonson is a member of the American Society of Heating and Air-Conditioning Engineers (ASHRAE).

The organization wrote in a statement that "ventilation and filtration provided by heating, ventilating, and air-conditioning systems can reduce the airborne concentration of SARS-CoV-2 and thus the risk of transmission through the air."

ASHRAE lists recommendations and checklists for schools and universities reopening in the fall on its website. 

School buildings have different systems, ages and ventilation rates, Simonson said, meaning there are different solutions to try to minimize the risk.

Even a ventilation system that provides 100 per cent outdoor air has limits when it comes to increasing the ventilation rate. While there is no simple solution for different types of ventilation systems, Simonson said every system should have good filters.

Another recommendation for schools is to turn on their ventilation systems one week before school starts, Simonson said, and to increase ventilation rates as much as possible.

HEPA filters

So called HEPA (High Efficiency Particle Air) filters are not uncommon in health care buildings such as hospitals.

They are considered to be very efficient and can filter out "99.9 per cent of particles within the air" including viruses, Blondeau said. The laboratory medicine environment in which Blondeau works requires those filters to keep staff save, he said.

Due to their higher costs and energy needs, these filters are not often used in regular places such as schools or offices, Simonson said.

HEPA filters are not the only solution for buildings though, with other filters also being able to do a "reasonable job", the professor said.

Ventilation systems at schools in Regina

CBC asked the Saskatoon Public School District (SPSD) and Regina Catholic School District (RCSD), which have released their back-to-school plans publicly, if they plan to improve their ventilation systems. 

SPSD said it is still building on its plan, although there is no mention of airflow or ventilation to date. 

"We are hoping to share more details with families later this week, which will include pertinent facilities information," said a spokesperson for SPSD in an emailed response to questions. 

The RCSD said it plans to introduce more fresh air to specific classrooms such as those used for automotive, cosmetology and welding classes.

"They are typically more interior classrooms, though not all," said an emailed response from the RCSD. 

"At this time, we've not needed to do anything differently with our ventilation systems." 

Outdoor activities

The federal guidelines for schools also advised moving activities outdoors when possible.

Blondeau said that although the likelihood of transmission is usually less outdoors compared to confined spaces, teaching outside is not a practical solution during Saskatchewan's harsh winters.

The Ministry of Education said in an email that school divisions are responsible for the execution of their return to school plans, including the opening of windows and outside teaching opportunities.