According to the current evidence, Covid-19 virus is primarily transmitted between people via respiratory droplets and contact routes when an infected person coughs, sneezes, sings, talks, or breathes.
Virus transmission in this outbreak could be explained by droplet transmission and the possibility that persons move around, touch surfaces, go to the restroom or engage in another close contact.
Indoor environments without good ventilation increase this risk, air conditioner prompted transmission of Covid-19; people in the airflow were at high risk for infection with SARS-CoV-2 in the poorly ventilated environment. The biggest problem in a closed environment/ room/ space is potential transmission through the airborne route—especially when the AC is on.
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Ventilation is an important factor in preventing the virus that causes Covid-19 from spreading indoors.
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Below are steps to to improve 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.
For mechanical systems, increase the percentage of outdoor air, using economizer modes of HVAC operations and potentially as high as 100%. - Before increasing outdoor air percentage, verify compatibility with HVAC system capabilities for both temperature and humidity control as well as compatibility with outdoor/indoor air quality considerations.
- Increase 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 minimize filter bypass.
- Consider running the HVAC system at maximum outside airflow for 2 hours before and after spaces are occupied, in accordance with manufactory 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.
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.
