COVID-19: Are outdoor patios safer than indoor dining?

As the colder weather sets in, the patios of Kingston normally start to disappear, but, like most things this year, the 2020 patio season will be a little different.

On Tuesday, Nov. 17, 2020, Kingston City Council voted in favour of extending the allowance of sidewalk patios through the winter. This was done to support safe business operation during the continued COVID-19 pandemic. Council heard that restaurants have found customers are more comfortable with dining on patios, as opposed to inside establishments, and extending the patio season allows restaurant owners to continue serving those customers in person.

But, with restaurants scrambling to winterize their patios, using awnings, tent structures, tent walls, and a variety of different ways to provide warmth, a lot of people have questioned just how safe these winterized patios will be in terms of COVID-19 transmission.

According to Kingston, Frontenac, Lennox and Addington (KFL&A) Public Health, there are a number of differences with regard to the probability of COVID-19 transmission when considering outdoor settings versus dining indoors at a restaurant. The following need to be considered:

• Physical distancing between parties continues to be an important part of limiting the spread of COVID-19.
• Whether dining inside or outside, there is an increased likelihood of COVID-19 transmission in these settings as there is often prolonged, unmasked, face-to-face interaction.
• Lack of appropriate ventilation in outdoor dining areas can also increase the risk of COVID-19 transmission in these setting.

KFL&A Public Health also pointed to a study from the National Collaborating Centre for Environmental Health (NCCEH), which was published on Wednesday, Nov. 18, 2020. Outdoor Winter Dining during the COVID-19 Pandemic, written by Angela Eykelbosh,explored how outdoor dining spaces can be adapted for colder weather in a way that to not exacerbate COVID-19 transmission. The study also looked at other safety risks associated with temporary enclosures.

In summary, that study found that dining, regardless of whether it is in- or outdoors, “heightens the risk of COVID-19 transmission.” As pointed out by KFL&A Public Health, this is due to the time spent unmasked with one or more other individuals whose health status is unknown.

“The first and most important means to decrease the risk of dining out is to dine with members of one’s own household or bubble,” the study reads. “Beyond this baseline risk, there are numerous innovative means to mitigate the risks specific to patio dining, which include the risk of COVID-19 transmission from other tables, and the risk of carbon monoxide exposure due to the inappropriate use of fuel-burning patio heaters.”

In consulting with experts within the NCCEH and its partner agencies, the study identified the following risks associated with outdoor winter dining:

• Enclosure, decreased ventilation, and the potential for increased COVID-19 transmission;
• Trying to fit more people into an outdoor space (i.e., non-compliance with physical distancing requirements) and the potential for COVID-19 transmission;
• Increased risk of fire and carbon monoxide (CO) exposure due to the misuse of fuel-burning heaters;
• Structural safety of temporary structures during inclement weather or heavy/wet snow fall;
• Egress in case of an emergency;
• Obstructing other users’ rights of way, particularly people with disabilities.

The study underlined that fuel-burning heaters should not be used within enclosures, and that restaurants should try to communicate the expected forecast to their potential diners, so that those diners can wear heavier clothing or bring their own blankets.

But in terms of possible COVID-19 transmission – both between those dining together and between those dining at other tables – it all comes down to the type of enclosure used protect diners from the elements, and how air is made to flow through those enclosures.

The study notes that, in the warmer weather, outdoor dining was preferable in terms of reducing possible transmission of SARS-CoV-2, the virus that causes COVID-19. This was especially true in patios or courtyards that didn’t employ awnings or any other type of coverage. However, the introduction of partial or full enclosures can present two undesirable conditions that should be avoided:

• Tight enclosures with limited air exchange. These increase the risk of particle accumulation and short-range aerosol transmission between parties.
• Creating drafty conditions. For example, the study looks at the lowering of two opposite walls of a tent (as opposed to two adjacent walls). This can result in funneling wind through the structure, and increases the likelihood that respiratory particles will be transferred among parties.

“The amount of enclosure required to provide thermal comfort varies geographically, and how that enclosure is configured will impact the risk of both droplet and short-range aerosol transmission. One option is to treat the patio space as an indoor space and manage it with a mechanical ventilation system that meets the standards for indoor spaces. However, this option may not be feasible for a variety of reasons (e.g., cost, space available on the public right of way, etc.),” the study reads.

“It is also important to note that temporary outdoor structures are still ventilated, but it is natural or passive ventilation, which is dependent on the velocity of air flows moving against the enclosure, the material of the enclosure, and the gaps/spaces through which air can leak. Thus, ventilation rates will vary with outdoor conditions, and this lack of control is a key issue in being able to provide a safe environment for diners.”

In conclusion, the study found that there are a variety of creative options that can be used to help patrons have a comfortable dining experience outdoors, even in the winter months. It noted that single-party enclosures have become a popular option that prevents between-party transmission, however, they do not mitigate – and may accentuate – the risk between those seated at the same table within them. It also noted that tents or enclosures should be designed with passive ventilation in mind, and should allow for rapid reconfiguration to modulate airflow as weather conditions change.

“Dining out heightens COVID-19 transmission risk because it requires unmasked, face-to-face interaction, and this risk exists both indoors and outdoors,” the study concludes.

“Thus, the most effective way to reduce transmission risk while visiting any public space is to avoid close contact with those outside one’s own ‘bubble’; in this case, restricting dining parties to members of one’s own household.”

KFL&A Public Health does inspect patios when a business first opens one, but not every time they open their patio or make adaptations. A patio (if open) would be inspected as part of regular, routine inspections, and currently those inspections would include specifications from the Re-opening Ontario Act. The local health unit is not inspecting each patio’s winterization techniques and installations.