Indoor Air Quality Monitoring in Office Buildings: What to Measure and How to Share It with Tenants

• The core office readings are carbon dioxide, fine particulate (PM2.5), total volatile organic compounds, temperature and relative humidity.
• There is no single legal limit for office air; programs such as RESET publish practical targets, such as PM2.5 under 12 µg/m³ and TVOC under 400 µg/m³ for high performance.
• CO2 tells you about ventilation, not overall air quality: ASHRAE says it does not give an overall indication of indoor air quality.
• 78% of U.S. workers in a 2025 Fellowes survey said it is important that their employer share air quality data.
• Fixed sensors give the trend in one spot; roaming checks cover the floor and help find where a problem starts.

Employees notice the air, and employers hear about it. In the 2025 Fellowes survey of 1,006 full time U.S. office workers, 94% said clean air helps them do their best work, and 45% of Millennial and Gen Z workers said they would consider leaving an employer over poor indoor air quality (Fellowes and Atomik Research, 2025).

That pressure reaches the lease. In CBRE's 2025 Americas Office Occupier Sentiment Survey, 37% of respondents named indoor air quality as a key amenity, and 43% said sustainable building features influence rent negotiations (CBRE, 2025).

Healthy buildings also show up in rent. An MIT Real Estate Innovation Lab study of offices in ten U.S. cities found Fitwel or WELL certified buildings earned roughly 4.4% to 7.7% more in effective rent per square foot than nearby peers (MIT, 2020).

Most office programs track five readings. Each one tells you something different about the building.

• Carbon dioxide (CO2): a proxy for how well outside air keeps up with the people in a space. It rises in full conference rooms and on floors where ventilation is short.
• Fine particulate (PM2.5): smoke, outdoor pollution that gets past the filters, and dust from construction or cleaning. Filter condition shows up here first.
• Total volatile organic compounds (TVOC): gases from new furniture, carpet, paint, cleaning products and printers. It spikes after fit outs and moves.
• Temperature: the number tenants complain about most, and a sign of zones the system is not serving well.
• Relative humidity: too low dries out people and materials, and too high invites mold.

Some buildings add formaldehyde, carbon monoxide near loading docks and garages, or ozone. For more on how these sensors work, see our guides to particulate sensing and VOC and gas sensing.

Read CO2 for what it is. ASHRAE's position is that indoor CO2 does not give an overall indication of air quality, and that ASHRAE 62.1 sets no CO2 limit based on health (ASHRAE, 2025). A low reading does not prove the air is clean, but a reading far above normal usually means ventilation is not working as designed.

No federal rule sets limits for general office air, so most owners borrow targets from a certification program or guideline. RESET Air is a common reference because it is built around continuous monitoring. Its commercial interior targets are (RESET via Kaiterra):

• PM2.5: under 35 µg/m³ acceptable, under 12 µg/m³ high performance.
• TVOC: under 500 µg/m³ acceptable, under 400 µg/m³ high performance.
• CO2: under 1,000 ppm acceptable, under 600 ppm high performance.

For humidity, the EPA advises keeping commercial buildings below 60% relative humidity, ideally 30 to 50% where possible, to limit mold (EPA). Temperature targets usually come from the lease and the building's design conditions.

ASHRAE 241, published in 2023, adds a different lens for infection risk: clean airflow per person rather than a pollutant reading, with 15 liters per second per person for offices (Kaiterra, 2024). It is a design and operating plan, not a sensor threshold, so treat it separately from day to day monitoring.

Fixed monitors give a continuous trend in one spot. RESET asks for at least one monitor per 5,382 square feet and per regularly occupied space type, mounted in the breathing zone 3 to 6 feet above the floor, with sensors recalibrated or replaced about every 12 months (RESET via Kaiterra).

On a large multi tenant floor, that adds up to many devices to buy, power, network and maintain. The monitors also only see the air around them, which can miss a printer room, a new fit out or a stuffy corner office.

Roaming checks fill the gaps. A reading taken at the same points every round shows how air changes across the floor, and a walk can follow a spike back to its source. Most buildings do best with both: fixed monitors in lobbies and large open areas, and roaming readings for everything between.

Air readings also sit naturally next to HVAC maintenance: a floor that drifts out of range is often a filter, damper or zone problem.

Workers want to see the data. In the Fellowes survey, 78% said it is important that their employer share indoor air quality data, and 36% said visible air quality monitors would build their confidence (Fellowes, 2025). For a landlord, that is a reason to publish rather than wait to be asked.

• Pick a short list: CO2, PM2.5, TVOC, temperature and humidity are enough for most tenants.
• Publish the targets: say which ranges you use and where they come from, so a reading means something.
• Show it where people look: a lobby screen for the building, and a tenant portal or monthly report by floor.
• Explain the exceptions: when a floor goes out of range, say why and what was done, such as a filter change or a damper repair.
• Keep claims modest: report measurements and actions, and avoid health promises the data cannot support.

A monthly summary per floor, with the readings over time and the work orders behind any changes, also fits well on a building digital twin, where tenants and engineers can see the same picture.

What is indoor air quality monitoring?

It is the regular measurement of readings such as CO2, PM2.5, TVOC, temperature and humidity in occupied spaces, so owners can spot problems, fix them and show tenants the results.

What should an office building measure?

Most programs track carbon dioxide, fine particulate (PM2.5), total volatile organic compounds, temperature and relative humidity. Some add formaldehyde, carbon monoxide or ozone.

Is 1,000 ppm of CO2 a legal limit?

No. ASHRAE says its ventilation standard sets no CO2 limit based on health, and that CO2 is not an overall indicator of air quality. Programs such as RESET use 1,000 ppm as an acceptable target.

How many air quality monitors does an office need?

RESET asks for at least one monitor per 5,382 square feet and per regularly occupied space type. Roaming checks can cover the areas between fixed monitors.

Should landlords share air quality data with tenants?

Most workers want it. In a 2025 Fellowes survey, 78% of U.S. workers said it is important that their employer share air quality data, and landlords are often where that data starts.

FacilityOps AI (RoboSkill Inc.) is an autonomous inspection platform that adds roaming air readings to the checks it already runs. A FacilityOps inspection robot walks the route across each floor on schedule and records readings at the same points every round, each with a time and location stamp.

• Floor by floor readings: VOC, particulate, temperature and humidity readings across open areas, conference rooms, corridors and mechanical spaces.
• Added sensors: the sensor hub can carry more sensors, such as CO2, where a program needs them.
• Finding the source: a reading out of range becomes a work order with a photo and location, and the next pass confirms whether it came back down.
• Tenant reporting: readings build a dated history by floor that can feed a monthly tenant summary or the building's digital twin.

Because the robot already walks these floors for other inspections, the air readings come without a separate device in every room, and they sit in the same record as the leak, thermal and fire safety checks from that round.

The robot runs fully autonomously, and technicians can take manual control at any time. The platform is hardware agnostic: robots and sensor hubs are the usual delivery, and drones, fixed monitors, other robots or a technician's handheld meter can feed the same record.

Every floor, every round: the air, measured and on record.

FacilityOps does not replace fixed monitors where a certification requires them, does not certify a building for RESET, WELL or Fitwel, and does not make health claims about the air.

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