Air change rate: a vital measurement in the fight against COVID-19
Recommendations from specialist ventilation and air-conditioning bodies all come to the same conclusion: that maintaining indoor air quality is vital in the fight against COVID-19 and other viruses, and that a ventilation system’s air change rate is of paramount importance.
Air flow meter and capture hood: how a measurement instrument helps protect against viruses
Air change rate is the speed at which all the air inside a room is replaced by the ventilation system. It is calculated as the air flow from each ventilation system inlet relative to the total volume of the room in question, and is expressed per hour. Some busy or sensitive rooms, such as hospital wards, open-plan offices and classrooms, require a constant air change rate.
Our DBM 620 air flow meter is the first measurement instrument in its class capable of quickly calculating air change rate. The app automatically combines air flow measurements from each ventilation inlet and works out the rate according to the volume of the room in question.
What air change rate is required to protect against COVID-19?
As this table indicates, the recommended air range change differs across various scenarios. The values were published before the COVID-19 pandemic. Even higher rates are now needed to prevent the virus from spreading indoors. In a hair salon, for instance, the sustained use of aerosols means that the ventilation system needs to complete between 10 and 15 air change cycles each hour.
Since viruses are often compared to aerosols on account of their physical behaviour, it makes sense that a high air change rate is required to reduce contamination risk. As the second table below shows, increasing the number of air changes per hour (ACH) from two to four decontaminates the room twice as quickly. But it still takes at least 69 minutes to remove all viral particles from the air. In order to achieve 99.9% removal efficiency in eight minutes, the air in the room would need to be changed no fewer than 50 times per hour!