Guidance · ASHRAE
ANSI/ASHRAE Standard 62.1: ventilation for acceptable indoor air quality
Indoor: ventilation design (USA)
ANSI/ASHRAE Standard 62.1, Ventilation and Acceptable Indoor Air Quality, is the ventilation design standard for commercial and institutional buildings in the United States: it sets minimum outdoor air rates by space type and occupancy, and procedures for designing ventilation systems to deliver them. It does not set a limit for indoor CO₂. ASHRAE's Position Document on Indoor Carbon Dioxide, reaffirmed in February 2025, says so explicitly and notes that misreadings of earlier editions still lead people to attribute a 1,000 ppm limit to ASHRAE.
Who it applies to
Who Uses It
Building designers and engineers, and the building codes that adopt it; classroom ventilation generally follows it. WELL v2 accepts ventilation designed and balanced to ASHRAE 62.1 as one way to meet its ventilation precondition, and employers managing office space often align with it because OSHA has no indoor air quality standard for offices.
Monitoring
How Monitoring Relates to It
Because 62.1 sets ventilation rates rather than concentrations, CO₂ is used as a proxy for how well a space is ventilated for its occupancy, and as the control input for demand-controlled ventilation. A CO₂ trend shows whether the outdoor air the design called for is actually reaching the room. The configurator assembles a monitor for CO₂ with temperature and humidity.
Recommended
best match-
Aethair IAQ built-in sensors
Compact plug-in monitor with every sensor built in, nothing to add. Ideal for straightforward indoor air quality monitoring.
Built-inCarbon Dioxide (CO₂)Also measures 12 more
Formaldehyde (CH₂O)Dew PointHeat IndexRelative HumidityParticle Count (by size)PM1PM10PM2.5Total PM / Mass Conc.Barometric PressureAir TemperatureVOC (Total)
Alternative
Aethair PRO-
Industrial monitor for indoor and outdoor sites. Built-in sensors cover the essentials, and hot-swappable gas sensor cartridges and a differential-pressure option add more.
Gas 1
Aethair CO₂ (dual NDIR)
Carbon Dioxide (CO₂)Dual-thermopile NDIR (non-dispersive infrared) sensing measures CO₂ with no chemical consumables, for…
Also fits: Aethair CO₂ (self-calibrating NDIR)
Gas 2
Free: one more gas sensor cartridge
MultiSense
Free: a MultiSense, stock or built to order
Expansion
Free: differential pressure
Also measures 13 more
Dew PointHeat IndexRelative HumidityIlluminance / LightParticle Count (by size)PM1PM10PM2.5Total PM / Mass Conc.Barometric PressureEquivalent Continuous Level (Leq)Sound Pressure Level (SPL)Air Temperature
Who measures each parameter
| Parameter | Aethair PRO | Aethair IAQ |  External |
|---|---|---|---|
| Carbon Dioxide (CO₂) | CO₂ (dual NDIR), CO₂ (self-calibrating NDIR) cartridges | Built in | 2 instruments via Thiamis |
Devices
Devices That Measure What ASHRAE 62.1 Relies On
How much of this standard one Aethair monitor covers, followed by the third-party instruments in the sensor catalog that measure its parameters. Each connects to Environet through a Thiamis gateway, which adds whatever the monitor leaves out.
Aethair monitors
Covers it on its own
Solutions
Solutions That Rely on ASHRAE 62.1
HVAC & Building Management
Monitor ventilation and filtration, with data for your BMS
Indoor Air Quality
Offices, schools, homes, and public buildings
School Air Monitoring
Classroom CO₂, particulates, and campus IAQ
Article Library
Articles on ASHRAE 62.1
Indoor Air Quality in Schools: Standards & Monitoring 2026
Indoor air quality in schools: which standards apply, what to monitor, and how CO2 and ventilation affect student attendance, health, and test scores.
Commercial Building IAQ Monitoring: ASHRAE 62.1 & WELL
Indoor air quality monitoring for commercial buildings: what to measure, which standards apply, and how property managers build a program tenants trust.
IAQ Monitoring Parameters: PM2.5, CO2, VOCs & Formaldehyde
Indoor air quality monitoring parameters explained: PM2.5, CO2, VOCs, and formaldehyde, plus the sensors, thresholds, and OSHA, ASHRAE 62.1, and WELL limits.
ASHRAE 170 Requirements and Which Edition Applies to You
ASHRAE 170 requirements explained: what the standard sets, which edition your facility is held to, what changed in 2025, and how each value gets verified.
Workplace Air Quality Monitoring for Offices and Employers
How to monitor workplace air quality in offices, what to measure for employee health and focus, and how continuous connected monitoring documents the result.
Types of Air Quality Monitors: Indoor, Outdoor, and Combined
Learn the three types of air quality monitors (indoor, outdoor, and combined), what each one measures, and when to use each one.
Questions
ASHRAE 62.1 FAQ
Does ASHRAE 62.1 set a CO₂ limit?
No. ASHRAE's Position Document on Indoor Carbon Dioxide states that Standard 62.1 does not provide a limit value for indoor CO₂; it sets minimum ventilation rates.
What does ASHRAE 62.1 set?
Minimum outdoor air ventilation rates by space type and occupancy, and procedures for designing ventilation systems that deliver them.
Why monitor CO₂ if ASHRAE 62.1 sets no limit?
CO₂ is a proxy for ventilation per occupant: a rising trend shows a space is getting less outdoor air than its occupancy needs, and it drives demand-controlled ventilation.
Monitor What ASHRAE 62.1 Relies On
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