COVID-19 vaccines are continuing to be rolled out, meaning that many office workers will likely be returning to their places of work in thenear future. For organisations and their employees, one of the safety considerations will be the air in their buildings.

Ventilation is an important factor in preventing the virus that causes COVID-19 from spreading indoors. Below are steps from the World Health Organisation (WHO) to consider in improving indoor ventilation. These steps should be considered in consultation with a heating, ventilation and air conditioning (HVAC) professional.

• Consider using natural ventilation, opening windows if possible and safe to do so.
• For mechanical systems, increase the percentage of outdoor air, using economiser modes of HVAC operations and potentially as high as 100%. Before increasing outdoor air percentages, verify compatibility with HVAC system capabilities for both temperature and humidity control as well as compatibility with outdoor/indoor air quality considerations.
• Increase the total airflow supply to occupied spaces, if possible.
• Disable demand-control ventilation controls that reduce air supply based on temperature or occupancy.
• Improve central air filtration:
  • • Increase air filtration to as high as possible without significantly diminishing design airflow.
  • • Inspect filter housing and racks to ensure appropriate filter fit and check for ways to minimise filter bypass.
• Consider running the HVAC system at maximum outside airflow for two hours before and after spaces are occupied, in accordance with manufacturers' recommendations.
• Generate clean-to-less-clean air movements by re-evaluating the positioning of supply and exhaust air diffusers and/or dampers and adjusting zone supply and exhaust flow rates to establish measurable pressure differentials. Have staff work in 'clean' ventilation zones that do not include higher-risk areas such as visitor reception or exercise facilities (if open).
• Ensure exhaust fans in restroom facilities are functional and operating at full capacity when the building is occupied.

In all workplaces, schools and tourist accommodation, there should be fresh, clean air. The WHO recommends an increased ventilation rate through natural or mechanical means, preferably without recirculation of the air. In case of air recirculation, filters should be cleaned regularly, especially for jobs that place an individual at a medium or high risk of exposure to COVID-19. Examples of such jobs may include frontline workers in retail, tourist accommodation and domestic workers.