Monitor Indoor Air Quality with the Ecobee Smart Thermostat Premium

The Ecobee Smart Thermostat Premium includes a built-in indoor air quality sensor that, in addition to temperature and humidity, monitors VOCs (volatile organic compounds) and reports estimated CO2 (eCO2), a CO2-equivalent value derived from the VOC sensor. For New Hampshire homes where tight construction has made ventilation a real consideration, having ongoing visibility into IAQ from the thermostat itself is genuinely useful. It also creates a built-in trigger for fan or ventilation runtime when air quality is poor.

At A.J. LeBlanc Heating, we install Ecobee Premium thermostats across southern New Hampshire. Here is what the sensors actually do and how to act on the data.

What the IAQ sensor measures

The Ecobee Premium's IAQ sensor tracks two main air quality indicators:

VOCs (volatile organic compounds)

VOCs are gaseous chemicals emitted from common household items: cleaning products, new furniture and carpet, paint, building materials, scented candles, cooking, and personal care products. Most are harmless at typical indoor concentrations; some are respiratory irritants or known long-term health hazards (formaldehyde, benzene).

The Ecobee sensor measures total VOCs (TVOC) rather than identifying specific compounds. The reading rises when VOCs are released (a freshly painted room, a new piece of furniture off-gassing, a cleaning session) and falls as ventilation dilutes them.

Estimated CO2 (eCO2)

The Premium does not measure CO2 directly. It estimates CO2-equivalent levels (eCO2) from the VOC sensor, since occupancy tends to raise VOCs and CO2 together. That makes eCO2 a useful ventilation indicator rather than a lab-grade CO2 measurement.

CO2 itself is exhaled by every person and pet in the home. In a well-ventilated space, indoor CO2 stays close to outdoor levels (around 420 parts per million). In a poorly ventilated space with multiple occupants, indoor CO2 can climb above 1,000 ppm within hours.

High indoor CO2 is associated with drowsiness, headaches, and reduced cognitive performance. Once concentrations exceed about 1,000 ppm, most people start to feel it; above 1,500 ppm, the effect is noticeable for almost everyone.

Why this matters more in NH

Modern New Hampshire construction and weatherization have made homes significantly tighter than they were 30 years ago. Tight construction is great for heating bills but reduces the natural air exchange that used to dilute indoor pollutants and CO2. Without intentional ventilation (an HRV, ERV, or even just running bathroom exhaust fans), tight NH homes can build up VOCs and CO2 to levels worth managing.

The Ecobee Premium's sensor gives you ongoing visibility into whether your home actually needs more ventilation, rather than guessing.

How to use the data

What "good" indoor air looks like

eCO2: treat the number as a ventilation indicator, not a precise CO2 measurement. Sustained readings under about 1,000 ppm equivalent suggest adequate ventilation; sustained readings above 1,500 ppm equivalent suggest the space needs more fresh air
VOCs: the sensor reports a relative quality scale (low, medium, high). Persistent "high" readings warrant investigation

What to do when eCO2 is high

Open a window briefly to refresh indoor air
Run a bathroom or kitchen exhaust fan to pull stale air out
For homes with HRV or ERV, increase the ventilation rate
Consider whether bedroom doors should be left ajar at night to allow air exchange
If eCO2 routinely spikes, the home may need a mechanical ventilation upgrade

What to do when VOCs are high

Identify the source if possible (recent cleaning, new furniture, paint, candles)
Increase ventilation until the reading drops
If VOCs are persistently elevated with no obvious source, consider an air quality assessment for the home
Activated carbon filtration can help capture VOCs but is not a substitute for ventilation

Using the thermostat to trigger ventilation

The Ecobee Premium can be configured to run the HVAC fan based on air quality readings. Combined with a fresh-air damper or HRV/ERV, this turns the thermostat into a passive ventilation controller:

Set the fan to run when the eCO2 reading crosses a threshold
For homes with an HRV or ERV, the Ecobee can call for ventilation when air quality drops
Combine with occupancy sensing to ventilate more when the home is occupied

How the Ecobee Premium fits in the lineup

Ecobee currently sells three main thermostat models:

Smart Thermostat Premium: includes the IAQ sensor, built-in voice control (Alexa), and the most advanced features. The right choice for homes where air quality is a priority.
Smart Thermostat Enhanced: same core scheduling, remote sensors, and equipment compatibility, without the IAQ sensor or built-in voice. The best value for most NH households.
Smart Thermostat Essential: entry model that replaced the Lite in 2025. Color touchscreen, works with Alexa, Google Home, and Apple Home, and supports SmartSensors (sold separately), but has no IAQ sensor or built-in voice. Suitable for simple single-zone systems or rentals.

Schedule an installation

If you are interested in adding indoor air quality monitoring to your NH home through an Ecobee Premium thermostat, or you want to discuss broader IAQ solutions (HRV, ERV, filtration), contact A.J. LeBlanc Heating. Serving New Hampshire families since 1928.

Frequently Asked Questions

What does the Ecobee Premium IAQ sensor measure?

It measures VOCs (volatile organic compounds) directly and reports estimated CO2 (eCO2) derived from the VOC reading, in addition to temperature and humidity. The readings are accessible in the Ecobee app and on the thermostat display.

What is a good indoor CO2 level?

For true CO2, below 800 ppm is great and below 1,000 ppm is acceptable. The Ecobee Premium reports estimated CO2 (eCO2) rather than a direct measurement, so treat sustained high readings as a sign the space needs more ventilation (open a window, run an HRV/ERV) rather than as an exact number.

Are VOCs dangerous?

At typical low indoor concentrations, most VOCs are not immediately dangerous. Persistent high VOC readings indicate a source worth identifying and ventilation worth increasing. Some VOCs (formaldehyde, benzene) have long-term health effects at chronic low exposures.

Can the Ecobee actually do anything about high readings?

Yes. The thermostat can be configured to run the HVAC fan or call for ventilation when air quality drops. For homes with an HRV or ERV, this provides automatic ventilation control.

Do I need the Premium model just for the IAQ sensor?

If indoor air quality is a priority (allergies, asthma, tight new construction, work-from-home situations where CO2 buildup matters), yes. For most other NH households, the Enhanced model is the better value.