Question
Stop treating 1,000 ppm CO2 as an ASHRAE pass/fail line
A widely repeated threshold can still be misattributed.
When it fits
- A dashboard colors 999 ppm green and 1001 ppm red because it claims ASHRAE requires that limit.
When to avoid it
- Other authorities and building codes may use explicit CO2 criteria for specific purposes; follow the applicable local requirement.
A question to ask
Which standard or building requirement actually applies? · Is the number absolute indoor CO2 or a differential above outdoors? · Is the goal ventilation management, cognition research or a regulatory exposure limit?
Why it matters
ASHRAE explicitly states that Standard 62.1 does not provide a universal indoor CO2 limit for acceptable IAQ and that claims of a 1000 ppm ASHRAE requirement are incorrect. Use building-specific ventilation guidance and trends rather than one universal traffic-light threshold.
An example
A home office hitting 1050 ppm is a reason to inspect ventilation, not proof that an ASHRAE safety limit was crossed.
Check your result
CO2 thresholds are cited to the correct standard and purpose rather than folklore.
Keep this limit in mind
- Other authorities and building codes may use explicit CO2 criteria for specific purposes; follow the applicable local requirement.
Evidence and sources
ASHRAE states Standard 62.1 does not set a universal 1000 ppm indoor CO2 limit for acceptable IAQ.
Other authorities and building codes may use explicit CO2 criteria for specific purposes; follow the applicable local requirement.
ASHRAE Position Document on Indoor Carbon Dioxide · See source record