What is the best indoor air quality monitor?

We do not rank products. For checking ventilation, the feature that matters most is a genuine CO2 sensor, sometimes called NDIR, rather than an estimated CO2 figure. Humidity sensing and a trend display are useful extras.

Do I need a CO2 monitor at home?

Not essential, but useful and inexpensive. A CO2 monitor shows whether fresh air is keeping up with the people in a room, which is otherwise invisible, and is handy in an airtight home or when troubleshooting stuffiness.

What type of CO2 sensor is best?

A genuine CO2 sensor, often described as NDIR, measures CO2 directly. Some cheaper devices estimate it from other readings, which can be inaccurate, so a real sensor is worth having.

Can a monitor tell me if my MVHR is working?

Yes, indirectly. If CO2 stays low in occupied rooms, the ventilation is keeping up. If it climbs and stays high with the system running, that suggests the MVHR is off, set too low or poorly commissioned.

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Indoor air quality monitors, explained

An indoor air quality monitor is a small device that measures things like CO2, humidity and fine particles in your home. For ventilation, the most useful measurement is CO2, which shows whether fresh air is keeping up with the people in a room. This guide explains what monitors measure and whether one is worth having.

By VentRight Editorial · Last updated 2026-07-08 · Impartial · Sourced

What does an indoor air quality monitor measure?

Most home air quality monitors measure some combination of carbon dioxide, humidity, temperature and fine particles, sometimes labelled PM2.5. Better ones also measure volatile organic compounds, or VOCs, from paints, cleaning products and furnishings. For checking ventilation, the CO2 reading is the most useful, because it rises when fresh air is not keeping up with the people in a room.

Different monitors focus on different things, so it is worth knowing what a given device actually measures rather than trusting a single air quality score. CO2 and humidity are the two most relevant to ventilation and condensation; particle and VOC sensing tell you more about outdoor pollution and indoor sources.

Do I need an indoor air quality monitor?

You do not need one, but it is a cheap and useful way to see whether your ventilation is working. A CO2 monitor in a bedroom or living room tells you if fresh air is keeping up, which is otherwise invisible. It is especially handy in an airtight home, or if you are troubleshooting stuffiness, condensation or poor sleep.

A monitor turns an abstract worry into something you can see and act on. If a bedroom feels stuffy in the morning, a monitor shows whether CO2 is climbing overnight and whether opening a vent or adjusting the ventilation fixes it. For most people it is a nice-to-have rather than essential, but an inexpensive one.

What should I look for in an air quality monitor?

For ventilation, choose a monitor that measures CO2 with a genuine sensor, sometimes called an NDIR sensor, rather than an estimated figure worked out from other readings. Humidity is worth having too, as it relates to condensation risk. A clear display, or an app that shows trends over time, makes it far more useful than a single snapshot.

We do not rank or sell products here, but the one feature that matters most for ventilation is a real CO2 sensor, because some cheaper devices estimate CO2 indirectly and can be inaccurate. Beyond that, being able to see how readings change through the day is what turns a monitor into a useful tool rather than a gadget.

How do I use a monitor to check ventilation?

Put the monitor where people spend time, such as a bedroom or living room, and watch the CO2 over a day. If it stays low, ventilation is keeping up; if it climbs high and stays there, fresh air is not reaching the room. Then test a change, opening a vent or checking the mechanical system, and see whether the reading improves.

This before-and-after approach is the most useful thing a monitor does: it shows whether a ventilation change actually works. If CO2 stays high even with a mechanical system running, that points to the system being off, set too low or poorly commissioned. See our guide to CO2 levels for what the numbers mean.

Questions

What is the best indoor air quality monitor?: We do not rank products. For checking ventilation, the feature that matters most is a genuine CO2 sensor, sometimes called NDIR, rather than an estimated CO2 figure. Humidity sensing and a trend display are useful extras.
Do I need a CO2 monitor at home?: Not essential, but useful and inexpensive. A CO2 monitor shows whether fresh air is keeping up with the people in a room, which is otherwise invisible, and is handy in an airtight home or when troubleshooting stuffiness.
What type of CO2 sensor is best?: A genuine CO2 sensor, often described as NDIR, measures CO2 directly. Some cheaper devices estimate it from other readings, which can be inaccurate, so a real sensor is worth having.
Can a monitor tell me if my MVHR is working?: Yes, indirectly. If CO2 stays low in occupied rooms, the ventilation is keeping up. If it climbs and stays high with the system running, that suggests the MVHR is off, set too low or poorly commissioned.