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 indoor environments. Users input their target air changes per hour through ventilation and information about the room, 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 supersede 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:
Calculated occupant density with 0 occupants is (0 per 1000 sq. ft.).(0 per 100 m2). This exceeds the max guideline used to set ventilation requirements for any building type:
(150 per 1000 sq. ft.).(150 per 100 m2).
If room 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.
Estimated CO2 concentration is based on a steady state. If the CO2 concentration of an indoor environment is increasing more than 50 ppm per 10 minutes, wait until levels reach a steady state before comparing to the results of this calculator.
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:
|Age (y)||Mean body mass (kg)||BMR (MJ/day)||CO2 generation rate (L/s)|
|Level of physical activity (met)|
|1 to <3||12.8||3.05||0.0015||0.0018||0.0021||0.0024||0.0030||0.0044||0.0059|
|3 to <6||18.8||3.90||0.0019||0.0023||0.0026||0.0030||0.0038||0.0057||0.0075|
|6 to < 11||31.9||5.14||0.0025||0.0030||0.0035||0.0040||0.0050||0.0075||0.0100|
|11 to <16||57.6||7.02||0.0034||0.0041||0.0048||0.0054||0.0068||0.0102||0.0136|
|16 to <21||77.3||7.77||0.0037||0.0045||0.0053||0.0060||0.0075||0.0113||0.0150|
|21 to < 30||84.9||8.24||0.0039||0.0048||0.0056||0.0064||0.0080||0.0120||0.0160|
|30 to <40||87.0||7.83||0.0037||0.0046||0.0053||0.0061||0.0076||0.0114||0.0152|
|40 to <50||90.5||8.00||0.0038||0.0046||0.0054||0.0062||0.0077||0.0116||0.0155|
|50 to <60||89.5||7.95||0.0038||0.0046||0.0054||0.0062||0.0077||0.0116||0.0154|
|60 to <70||89.5||6.84||0.0033||0.0040||0.0046||0.0053||0.0066||0.0099||0.0133|
|70 to <80||83.9||6.57||0.0031||0.0038||0.0045||0.0051||0.0064||0.0095||0.0127|
|1 to <3||12.3||2.88||0.0014||0.0017||0.0020||0.0022||0.0028||0.0042||0.0056|
|3 to <6||18.3||3.59||0.0017||0.0021||0.0024||0.0028||0.0035||0.0052||0.0070|
|6 to < 11||31.7||4.73||0.0023||0.0027||0.0032||0.0037||0.0046||0.0069||0.0092|
|11 to < 16||55.9||6.03||0.0029||0.0035||0.0041||0.0047||0.0058||0.0088||0.0117|
|16 to <21||65.9||6.12||0.0029||0.0036||0.0042||0.0047||0.0059||0.0089||0.0119|
|21 to < 30||71.9||6.49||0.0031||0.0038||0.0044||0.0050||0.0063||0.0094||0.0126|
|30 to < 40||74.8||6.08||0.0029||0.0035||0.0041||0.0047||0.0059||0.0088||0.0118|
|40 to <50||77.1||6.16||0.0029||0.0036||0.0042||0.0048||0.0060||0.0090||0.0119|
|50 to <60||77.5||6.17||0.0030||0.0036||0.0042||0.0048||0.0060||0.0090||0.0120|
|60 to <70||76.8||5.67||0.0027||0.0033||0.0038||0.0044||0.0055||0.0082||0.0110|
|70 to <80||70.8||5.45||0.0026||0.0032||0.0037||0.0042||0.0053||0.0079||0.0106|
|Child care||2.0 to 3.0|
|Cleaning, sweeping—moderate effort||3.8|
|Health club exercise classes—general||5.0|
|Kitchen activity—moderate effort||3.3|
|Lying or sitting quietly||1.0 to 1.3|
|Sitting reading, writing, typing||1.3|
|Sitting at sporting event as spectator||1.5|
|Sitting tasks, light effort (e.g, office work)||1.5|
|Sitting quietly in religious service||1.3|
|Standing tasks, light effort (e.g, store clerk, filing)||3.0|
|Walking, less than 2 mph, level surface, very slow||2.0|
|Walking, 2.8 mph to 3.2 mph, level surface, moderate pace||3.5|
The default occupant density was assumed based on ASHRAE Standard 62.1-2019: Ventilation for Acceptable Indoor Air Quality
Persily, A. and de Jonge, L., 2017. Carbon dioxide generation rates for building occupants. Indoor air, 27(5), pp.868-879 (Tables 3 and 4.)