This tool was developed to support the use of real-time carbon dioxide (CO2) sensors indoors as a way to help evaluate ventilation rates in classrooms. Users input their target air changes per hour through ventilation and information about the classroom, and the calculator returns the estimated CO2 concentration.
Important: sufficient clean air delivery can be achieved through any combination of outdoor air ventilation and filtration, but this tool is only for assessing outdoor air ventilation. It is possible to exceed these target CO2 concentrations and still be meeting targets for clean air through filtration.
This guidance does not supercede state or local guidance or guidance from CDC, WHO, or other bodies. It is provided to support efforts to understand ventilation rates in indoor spaces.
|Ideal (6 ACH)||Excellent (5-6 ACH)||Good (4-5 ACH)||Minimum (3-4 ACH)||Low (< 3 ACH)|
|Ideal (6 ACH)||Excellent (5-6 ACH)||Good (4-5 ACH)|
|Minimum (3-4 ACH)||Low (< 3 ACH)|
Configure the settings and then click the button below to calculate.
Your CO2 concentration estimate:
Note: This occupant density exceeds the default density used to set ventilation requirements for schools.
If classroom CO2 consistently exceeds the above calculation:
This air cleaner calculator can be used to explore portable air cleaner options. Since portable air cleaners increase total effective ACH, but do NOT reduce indoor CO2 concentrations, use the linked portable air cleaner calculator, and NOT indoor CO2 measurements, to assess total effective ACH when using portable air cleaners.
*Strategies two and three increase total effective ACH, but do not change the indoor CO2 concentration. Only strategy one (increasing outdoor air ventilation) reduces the indoor CO2 concentration while also increasing total ACH. Implementing strategy two and/or three will reduce the portion of the total target ACH that will be provided by outdoor air ventilation, which can be helpful if the ventilation system has operational limitations.
This estimate of the steady-state CO2 concentration is based on the number of people, an estimate of their ages and activity level, the room dimensions, and the outdoor air ventilation only. This calculator makes the following necessary assumptions to perform this simplified calculation:
|Elementary School||0.0076279752||0.0128192361||6 to < 11|
|Middle School||0.0100646895||0.016951056||11 to < 16|
|High School||0.0107003541||0.0182223852||16 to < 21|
|Adult||0.0107003541||0.0183283293||30 to < 40|
Source: Table 4 in Persily & de Jonge 2017
|Standing/light effort||3 met|
Source: Table 3 in Persily & de Jonge 2017
|Age bracket||Occupant Density||Note|
|5 to 8 years old||25 people/1000 sq. ft.||Used for elementary school ages in this calculator|
|>= 9 years old||35 people/1000 sq. ft.||Used for students older than elementary school ages in this calculator|