What an office air quality monitor should track

Office air quality monitoring tracks five readings in the rooms people actually work in: CO₂ in ppm, PM2.5 in µg/m³, VOCs, temperature in °F and relative humidity in %, each checked against the air outside. A monitor that reports just one of those answers just one question.

A phone booth that felt fine at nine in the morning turns thick by the third call of the day, and nobody on the facilities team can say whether that is the HVAC schedule, the room's size, or just a feeling. An open floor with forty desks reads nothing like the glass conference room next to it, even on the same afternoon.

This post covers the five readings an office air quality monitor should track, what each one means, where to put a monitor across different office spaces, and what to try once one of them moves.

Key Takeaways

• Office air quality monitoring covers five readings: CO2 in ppm, PM2.5 in µg/m³, VOCs, temperature in °F and relative humidity in %, each checked against the air outside.
• CO2 above roughly 1,000 to 1,100 ppm in an occupied room is the common sign that outdoor air ventilation hasn't kept up, per ASHRAE's position.
• A good PM2.5 reading stays under 9.0 µg/m³ as a daily average, the top of the EPA's Good band for fine particles.
• VOCs run two to five times higher indoors than outdoors even without an obvious source, per EPA testing, and a newly painted or recarpeted room is worth its own reading.
• A monitor tells a facilities team what a room is doing. It does not adjust a damper or fix a leak by itself.

The five readings an office air quality monitor should track

"Air quality" in an office breaks into five separate readings, each answering a different question:

• CO₂ (ppm): how stale a room is getting, which tracks outdoor air ventilation more than anything burning or off-gassing.
• PM2.5 (µg/m³): fine particles from nearby traffic, a shared kitchen, wildfire smoke or renovation dust.
• VOCs: off-gassing from new paint, carpet, furniture and cleaning products.
• Relative humidity (%): too high and surfaces stay damp long enough for mold; too low and a room gets dry and irritating.
• Temperature (°F): comfort, and a check on whether the HVAC system is keeping pace with the room.

Each of those readings means more once it is checked against the air outside the building that day. A kit that reports all five, room by room, against that outdoor reference, tracks an office floor the way people actually experience it: one room at a time, not as a single average for the whole building.

CO₂: the fastest signal in a packed room

CO₂ rises and falls with occupancy, which makes it the fastest way to tell whether a room's fresh air supply is keeping up. ASHRAE's position sets the indoor ceiling at about 700 ppm over the outdoor level, which runs close to 420 ppm, for a practical limit near 1,100 ppm. A room can read above that and still feel fine on the thermostat, since CO₂ and temperature measure two different things.

Many offices run the outdoor air damper on a schedule built for a nine to five day, so a room that books back to back all morning, or one still full for a seven o'clock call with a different time zone, gets the same fixed amount of outdoor air as an empty one. A line that climbs through a Tuesday and barely moves on a quiet Friday is the pattern that tells a facilities team the schedule needs widening, or that outdoor air should be tied to a sensor instead of a clock.

PM2.5 and VOCs: what gets in from outside and off-gases inside

PM2.5 is judged against the air outside the building that day. A good indoor reading stays under 9.0 µg/m³ as a daily average, the top of the EPA's Good band. On a wildfire smoke day, indoor PM2.5 tracks roughly 55% to 60% of the outdoor level once windows and doors stay shut, so a smoky day outside still moves the office reading, especially near a loading dock or a street-facing entrance that gets propped open all day.

VOCs come from a different source: the building itself. The EPA has measured common VOCs running two to five times higher indoors than outdoors, even with no obvious source in the room. A floor that was just repainted or recarpeted will read higher than that for days afterward, since fresh paint, new carpet and new furniture keep off-gassing after the crew leaves. There is no single VOC number the way there is a PM2.5 scale, but a rising line is a reason to go looking for a source, the same way a stuffy room points toward CO₂.

Temperature and relative humidity across floors

Relative humidity has a defined range worth tracking: the EPA's guidance keeps it under 60%, with 30% to 50% recommended, to avoid the condensation that lets mold take hold. A roof leak or a door that never sealed right can push a floor above that line for weeks before anyone notices, usually once a musty smell shows up or a stain starts working across a ceiling tile.

Temperature is less a health reading than a comfort and equipment check. A room running several degrees warmer than the setpoint, alongside a climbing CO₂ line, usually points to the same cause: not enough outdoor air is getting in.

Office air quality monitoring across a floor plan

A monitor belongs in the room, not in a hallway meant to stand in for the whole floor. A glass conference room near the elevator bank, a bank of phone booths, an open section of forty desks and a break room next to the kitchen rarely read the same on the same afternoon, so one reading for the whole floor hides whichever of those spaces is actually the problem.

Where it sits inside the room matters too. Set it away from the supply vent and any open door, roughly at head height for someone seated at a desk, not mounted near the ceiling where the air has already mixed with whatever the HVAC system just pushed out. A room that was recently painted or recarpeted is worth a reading on its own, separate from the rest of the floor.

What to try once a reading moves

A reading points at the problem. Somebody still has to act on it, and the fix depends on which number actually moved.

• CO₂ climbing: check the outdoor air damper schedule first. A fixed schedule built for a standard workday will not stretch to cover a room that runs busier, or later, than that day assumes.
• PM2.5 climbing: confirm the windows and doors near that space are actually shut on a smoke day. Past that, a MERV 13 filter in the HVAC system only helps while the fan is moving enough air through it.
• VOCs climbing: look for what changed in the room: new paint, new carpet, a furniture delivery. Ventilating the space directly brings the number down faster than anything else.
• Humidity climbing: find the water source first, a roof leak above a corner office, a loading dock door left open in the rain, a bathroom exhaust fan that stopped pulling air, before reaching for a dehumidifier.

None of it happens on its own. A reading replaces "this room feels off" with a specific number, but someone still has to open a ticket and follow through on it.

FAQ

What should an office air quality monitor track? An office air quality monitor should track CO2, PM2.5, VOCs, temperature and relative humidity in the rooms people occupy, each checked against the air outside that day. Reporting only one of those answers only one of the questions a facilities team actually has.

What is a good CO2 level for an office? A good CO2 level for an office stays under roughly 1,000 to 1,100 ppm, the range ASHRAE treats as a sign that outdoor air ventilation is keeping up with occupancy.

Where should an air quality monitor go in an office? In the specific room in question, not a hallway chosen to speak for the whole floor. A conference room, a bank of phone booths and an open floor section read differently even on the same afternoon, so each deserves its own reading, placed away from vents and doors at roughly head height.

Does an office need to monitor VOCs? Any office that has recently painted, recarpeted or brought in new furniture benefits from tracking VOCs, since those sources run two to five times higher than outdoor air even without an obvious smell, per the EPA. A rising line is a reason to go looking for the source.

How often should office air quality be monitored? Continuously, not on a schedule. A quarterly check might land on a quiet Tuesday and miss the pattern entirely, while a monitor left running catches the afternoon climb in the booked conference room every time it happens.

The next step for a facilities team

Office air quality monitoring is five readings, not one score: CO2 for ventilation, PM2.5 for what blew in from outside, VOCs for what the building itself is off-gassing, and temperature and humidity for comfort and mold risk. A conference room past 1,100 ppm of CO2 needs a damper schedule that matches when people actually book it. A floor letting PM2.5 past 9.0 µg/m³ on a smoke day needs its doors checked and its filter confirmed, not assumed. A freshly painted section worth watching for VOCs needs a window open, not a guess about when the smell will fade.

For the regulatory side of the same question, OSHA indoor air quality standards covers what a facilities team is actually required to do, and workplace air quality testing covers the difference between a one-time test and monitoring that keeps running.

A facilities team that wants that evidence before the next complaint, not after it, can start with a short form on Measured Air's page for commercial buildings. Measured Air replies within a business day.