It is known that buildings are often the protagonists of the spread of infections through the air. The chances of infection depend on the size of the room and the number of people in it.

According to the US Centers for Disease Control and Prevention (CDC). In the U.S., infectious diseases can spread when an infected person coughs, sneezes speak or exhales droplets and tiny particles that contain viruses or bacteria. These droplets and particles can be inhaled by other people or fall into their eyes, noses, or mouth.

In this sense, it is important to know the amount of ventilation needed in an interior space. For this, Standard 62.1 Ventilation for acceptable indoor air quality describes minimum ventilation rates based on the combination of cubic feet per minute (cfm) per person and per square foot of surface, and both are related to the type of occupation.


How do you know how much ventilation is needed?

According to standard 62.1, museums/galleries require a minimum combined outdoor air rate of 9 cfm/person, while animal areas in pet stores or weight rooms in gyms require no less than 26 cfm/person. Office spaces require 17 cfm/person; however, the seating area of an auditorium requires only five cubic feet per minute per person.

Likewise, it is also recommended that households receive 0.35 air changes per hour, but not less than 15 cubic feet of air per minute per person.


Are there alternatives to ventilation?

Another way to reduce the risk of disease transmission is to reduce the capacity in a room. This allows for social distancing, which in turn reduces the risk of transmission by close contact. Also, as an additional benefit, more outdoor air is provided per person, which contributes to better overall air quality.

If we looked at a 1,000-square-foot classroom and reduced the number of people from 35 to 17, the ventilation rate would provide twice as much outdoor air per person. In the 1,000-square-foot living room with a 10-foot ceiling and a ventilation rate of 500 cfm of outdoor air, with 17 people, it allows maintaining 26 cfm/person of outdoor air, and up to three air changes per hour.


How much does it cost to improve air systems to meet the proper ventilation levels?

The increase in air exchange rates implies additional costs, although everything depends on space, so it is not always the case. According to the CDC, these may be the estimated costs:

$0: Open windows, inspect and maintain dedicated exhaust ventilation, disable on-demand controlled ventilation (DCV) controls and reposition outdoor air vents
Less than $100: use of fans to increase the effectiveness of open windows and relocation of diffusers or supply/exhaust fans to create directional airflow
$500 or more: Addition of high-efficiency portable filter/fan systems for particle absorption (HEPA).


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