Ventilation and air circulation

Prevent the spread of communicable disease

Public health experts advise that moving activities outdoors whenever possible can minimize the spread of communicable disease. For indoor activities, you can improve indoor air quality by supplying outdoor air, which will help remove and dilute contaminants that naturally accumulate in indoor settings, especially in well-sealed buildings.

Frequently asked questions

At this time, there is no evidence that a building’s ventilation system, in good operating condition, contributes to the spread of communicable disease.

Employers must ensure that a place of employment is adequately ventilated by mechanical ventilation that conforms to ASHRAE standard 62-1989, “Ventilation for Acceptable Indoor Air Quality." See section 20(1)(b) of Regulation 91-191.

Make sure preventative maintenance is conducted according to the manufacturer’s requirements (for example, regular filter changes and inspection of critical components).

Make sure the system is properly balanced. Verify that the system meets its design conditions for air flow, temperature, pressure drop, noise and vibration.

If you’re using portable fans or air conditioning units, make sure they’re set up to avoid blowing air directly from one person’s breathing zone to other occupants of a room. Avoid horizontal cross breezes. Instead, set up the devices so air flow moves downward from the ceiling.

Reduce air recirculation and increase the outdoor air intake as much as possible while maintaining a comfortable indoor temperature and humidity. Make sure outdoor air dampers are operating properly.

Do not turn off the ventilation system while the building is occupied. After working hours or on weekends, consider turning the system down, rather than turning it off.

Workers using company vehicles should adjust the vents or air conditioning controls to allow outdoor air to flow in. Do not set the vents to recirculate.

Leave windows partially open to allow as much outdoor air as possible into the vehicle.

If the building has been unoccupied for an extended period of time, make sure your system has a thorough inspection before it’s put back into operation. Refer to the manufacturer specifications for details on inspection requirements. If your building system includes a cooling tower, you must assess the risk of Legionnaire’s Disease contamination and disinfect your system as required by the manufacturer.

HVAC maintenance workers must follow their usual safe work procedures, including the use of personal protective equipment normally worn to conduct maintenance. No special cleaning or disinfecting of the system is necessary when usual safe work procedures are followed.

Employers must ensure that a place of employment is adequately ventilated by natural ventilation, which introduces outside air provided by openings having a combined area equal to at least five per cent of the floor area. See section 20(1)(a) of Regulation 91-191.

When advised by Public Health, post occupancy limits to allow for adequate physical distancing in every room. Don’t allow overcrowding.

Air cleaning devices that have a High Efficiency Particulate Air (HEPA) filter will reduce particles in the air. You can use them in a room with poor circulation.

WorkSafeNB recommends that workplaces increase or maximize their existing ventilation systems as a first step to controlling the spread of COVID-19. Ventilation systems must ensure enough fresh air is brought in to keep air contaminant concentrations low enough to meet ASHRAE Standard 62 “Ventilation for Acceptable Air Quality”. A properly designed, operated, and maintained mechanical ventilation system (when combined with policies that keep symptomatic people from coming to work) is the most effective measure for controlling the risk of COVID-19 transmission.

For workplaces that do not have mechanical ventilation systems, WorkSafeNB requires the use of natural ventilation such as keeping windows or doors open to provide sufficient fresh air to enter the workplace to meet the criteria established in the ASHRAE Standard. We understand open windows and doors may cause additional issues for the workplace, especially during cold weather season and it may not be possible to be maintained throughout the day. However, if you do not allow enough fresh air into the building to reduce air contaminant concentrations, the risk of COVID-19 transmission will be elevated. 

As an alternative, a combination of intermittently opening windows and doors and the use of HEPA filtration units may reduce the risk of exposure. Each workplace needs to perform an assessment to decide how long windows and doors should remain open for each hour, along with how many HEPA units are necessary to remove the air contaminants from the air.

PHAC advises, when properly used, portable air filtration devices with high-efficiency particulate air (HEPA) filters have been shown to reduce the concentration of some viruses from the air. The use of these devices could be considered as an additional protection in situations where enhancing natural or mechanical ventilation is not possible and when physical distancing can be achieved.

It's important to note that the effectiveness of portable air filtration devices in reducing the transmission of the SARS-CoV-2 virus has not yet been demonstrated. As such, they should not be used alone or as replacement for adequate ventilation, physical distancing, and hygienic measures. Whenever possible, consider the use of an alternative space, or preferably gathering outdoors rather than indoors, when interacting with people from outside your household.

To select the right air filtration device, it is important to consult an experienced professional to:

  • help identify ventilation needs
  • explain the steps for proper maintenance
  • ensure the unit has a high enough clean air delivery rate and is installed properly

When in use, ensure the air released by the device is not blown directly at individuals as it can increase the spread of droplets.

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