Your monitor jumps to 1,800 ppm and just sits there, and now you're wondering if something's actually wrong with your house or if the little device on your shelf is just being dramatic. Both are possible. Here's how to tell which one you're actually dealing with.

Start with what a normal range even looks like

Outdoor air runs around 420 ppm. A well-ventilated room with a few people in it typically sits somewhere in the 600 to 1,000 ppm range. Above 1,000 ppm, most people start to notice mild effects like drowsiness or trouble concentrating. Above 2,000 ppm, that fogginess tends to get more pronounced. None of these numbers are dangerous in the way carbon monoxide is; CO2 buildup is a sign of stale, under-ventilated air, not a poisoning risk at typical home concentrations. So a reading of 1,400 ppm in a closed bedroom overnight isn't an emergency. It's information.

A closed-house event: the most common explanation by far

If the spike happens at night, in a room with the door and windows shut, with people or pets sleeping in it, this is almost always just people breathing in a sealed space. Every exhale adds CO2, and a bedroom holds that CO2 in without anywhere to go until air actually gets exchanged. This is the simplest explanation and the one to rule out first: did the number climb overnight in a closed room with people in it? If yes, you've probably found your answer, and it's not a problem with your house.

A ventilation problem: when the pattern doesn't resolve on its own

The distinction between a normal closed-room spike and an actual ventilation issue is what happens when you open the door or turn on ventilation. If cracking a window or running your HVAC fan brings the number down within twenty or thirty minutes, your ventilation is working fine, it just needed a nudge. If the number stays elevated even with normal daily airflow, doors opening and closing, HVAC cycling, that points to something more structural: a home that's been sealed tighter than its ventilation system can keep up with.

This shows up more in newer, energy-efficient homes than older ones. Tighter building envelopes are good for energy bills but mean the home doesn't exchange air with the outside as readily unless there's a mechanical system designed to do it. If your home has an ERV or HRV (a system that swaps indoor and outdoor air while recovering heating or cooling energy), check that it's actually running and hasn't been switched off, disconnected, or left in a low setting since move-in. It's common for these systems to be installed but not properly commissioned, meaning they're present but not doing their job.

A one-time event: something specific happened, and it'll pass

Some spikes have a clear, temporary cause rather than an ongoing structural one. A dinner party with ten people in a small dining room. A home gym session in a closed room. A gas stove or oven running for an extended stretch, gas combustion produces CO2 as a byproduct alongside other combustion gases, which is part of why kitchen exhaust matters during cooking, not just for smoke and grease. A fireplace or space heater running without adequate fresh air. These situations produce a real spike that resolves once the activity stops and the room gets a normal amount of airflow. If you can point to a specific thing that happened right before the number climbed, that's usually your answer, and no structural fix is needed.

A sensor problem: when nothing about the pattern makes sense

If your monitor reads high in an empty, well-ventilated room with no one in it and no combustion source running, or if the number seems stuck rather than fluctuating with occupancy the way CO2 naturally does, suspect the sensor itself. Non-dispersive infrared sensors, the accurate kind used in most decent consumer monitors, can drift out of calibration over time, and cheaper sensors are more prone to this than others. A number that never changes regardless of what's happening in the room, or one that reads implausibly high (5,000+ ppm) without an obvious cause, is more likely a device problem than a real air quality event.

A quick way to sort it

• Spike only at night, only with people in a closed room: normal closed-house buildup, not a problem
• Spike resolves fast once you open a window or run the fan: ventilation is fine, just needed airflow
• Spike persists despite normal daily airflow: possible ventilation system issue, check your ERV/HRV
• Spike tied to a specific activity (cooking, a gathering, a workout): a one-time event, nothing to fix
• Spike doesn't track with occupancy or activity at all: suspect the sensor

Where the iAdaptAir fits into this

The iAdaptAir doesn't measure CO2 directly, its particle sensor is built for PM2.5 and general air quality, not gas concentration. But it plays a real role in the broader picture: if you're running it in a closed bedroom overnight, keeping the door shut for containment, you're also concentrating CO2 in that same sealed space. Cracking the door slightly or running the room's ventilation periodically alongside the purifier keeps both particle levels and CO2 in check, rather than trading one problem for another.

A high CO2 reading isn't a verdict. It's a starting point, and the pattern around it tells you which explanation actually fits.

Shop Air Oasis and find the iAdaptAir sized for your space. Breathe Better, Live Better.