Indoor Air Quality and Ventilation

Measuring and evaluating air quality is an important activity to reduce potential health risks to the people of Saskatchewan.

Airborne viruses, including COVID-19, spread between people easier indoors than outdoors. The use of ventilation mitigation strategies can reduce the spread of airborne viruses indoors.

In addition to providing air circulation and thermal comfort for occupants in indoor spaces, a properly installed and maintained heating, ventilation, and air conditioning (HVAC) system can reduce the amount of infectious particles in the air and help reduce communicable disease transmission.

To achieve optimal performance, an HVAC system must be configured to meet the specific dimensions and uses of the ventilated space. Maintenance of the HVAC system should be performed according to the manufacturer's operation manual. Consult with an HVAC professional, if necessary.

Ways to Improve your Indoor Ventilation

• Increase airflow by opening doors and windows. Ensure windows are properly screened.
• Be mindful of sensitivities to outdoor allergens. Allergens can trigger respiratory reactions, including asthma attacks, and result in the onset of allergy symptoms.
• Reduce or eliminate the HVAC system's closed-circuit air recirculation (recirculation mode) if outdoor air quality is good.
• Use fans to increase the effectiveness of open windows. Run fans at lower speeds, directing the output towards the outdoors (opened window) or towards an unoccupied space.
• Improve ventilation system filtration. A filter's ability to capture particles is measured by its Minimum Efficiency Reporting Value (MERV). Small particles, including viruses, can be trapped by filters rated
  MERV-13 or higher.
• Ensure filters are properly sized and are changed regularly. HVAC units should use the highest-rated filters that the system can accommodate.
• Maintain an optimal indoor humidity level between 30 and 50 per cent.
  • Lower humidity levels can cause aerosol sizes to shrink, resulting in the aerosols staying suspended in the air for longer. Higher humidity levels can create condensation on surfaces, which can lead to mould growth.

Ventilation Additions and Enhancements

Portable high-efficiency particulate air (HEPA) purifiers

• Where there is insufficient ventilation and filtration, the use of portable HEPA purifiers (a.k.a. air scrubbers or air cleaners) may be considered. Unit filters should be sized and changed according to manufacturer’s instructions to effectively reduce indoor respiratory particles.
• As described by the National Collaborating Centre for Environmental Health (NCCEH), portable air cleaners can be used to reduce particulate matter exposure in several different contexts, such as:
  • Reducing the presence of respiratory pathogens.
  • Removing smoke that gets indoors during wildfire events.
  • Reducing indoor exposure to pollen during allergy season.
  • Preventing exposure to everyday pollutants and allergens (e.g. mould, animal dander, traffic exhaust, dust).

• Portable air cleaners should run continuously and be positioned so they do not obstruct airflow (do not place too close to furniture or walls). Like fans, air cleaners should not be positioned in a manner that will increase the person-to-person exchange of airborne particles.

Do-It-Yourself (DIY) air cleaners

• A recent study conducted by the NCCEH found that DIY air cleaners appear to be a valuable, low-cost tool to reduce hazardous particulate matter exposure.
• The best DIY design will depend on multiple factors, including available space, activities carried out and noise disruption. The Clean Air Delivery Rate (CADR) can vary substantially depending on material quality; it may be useful to evaluate DIY air cleaner effectiveness post-construction using low-cost particulate matter sensors.

Carbon Dioxide Indoor Sensors

• Carbon Dioxide (CO₂) sensors may be useful detecting ventilation issues in indoor spaces. When occupants remain in enclosed spaces for extended periods, their expired CO₂ accumulates if the air within the space is not exchanged with fresher outdoor air.
• Immediate corrective actions may include increasing the mechanical ventilation rate, increasing the fresh air exchange rate, reducing occupancy or opening windows and doors.

CO₂ levels in an occupied space do not directly correlate with the transmission risk of airborne viruses, including COVID-19. For accurate CO₂ measurements, monitors must be strategically located. Ideally, sensors should be installed between 0.5 m and 2 m above the floor.

Do not place sensors:

• at or near a window
• near an air supply intake for a mechanical ventilation system
• within two meters of any human occupant
• within two meters of an open flame

Digital CO₂ sensors are easy to read, but they are also easy to misinterpret. Expertise may be required to interpret the CO₂ concentrations and provide advice on occupant health. Even when CO₂ monitoring results are acceptable, the HVAC system should be maintained and assessed periodically to ensure that it is performing as designed. Consultation with a professional is recommended at regular intervals

Complaints

Public health inspectors ensure safe air quality by responding to complaints about indoor air quality in public buildings and rental units.

Complaints may be related to health effects associated with:

• Carbon monoxide
• Mould
• Nitrogen dioxide
• Carbon dioxide
• Formaldehyde

Depending on the type of concern, public health inspectors also provide advice on indoor air quality issues related to private residences.

Public health inspectors also monitor air quality in ice arenas where air quality may be a health concern.

• Ice resurfacing equipment can produce exhaust gases and combustion products (e.g. carbon monoxide and nitrogen oxide).
• Improperly operated or poorly maintained ice resurfacing equipment and facility ventilation systems may allow exhaust gases to accumulate indoors which may make people sick.

The Air Quality Health Index is a tool developed by Environment Canada to help you understand what the air quality means to your health.

Complaints about air quality, except those related to a workplace environment, may be directed to the Saskatchewan Health Authority.

For more information related to the workplace environment, visit Safety in the Workplace.

Additional information and resources on indoor ventilation in public and private spaces:

• Health Canada Video - COVID-19: Ways to improve ventilation and air filtration in your home
• Health Canada Poster - Ventilation helps protect against the spread of COVID-19
• Government of Canada – COVID-19 and ventilation
• NCCEH – COVID-19 ventilation and transmission risk
• NCCEH indoor CO2 sensors.
• NCCEH CO2 sensors in schools.
• The Lancet. Respiratory Medicine. US CDC announces indoor air guidance for COVID-19 after 3 years