Learn
What your CO2 readings mean, how to measure fairly, what to try for free, and how to buy ventilation well if you need it. Every guide ends with something to try tonight or this week.
The goal for a bedroom: 800 ppm or less, on average, while you sleep. From a 2025 review of 17 sleep studies for ASHRAE; sleep was measurably more disturbed from about 1,000.
Why 800 · The research · How to get there · Questions and answers
Air basics
What CO2 readings tell you, and what they don’t.
Why is my bedroom stuffy in the morning?
5 minFine at bedtime, close and stale by morning: why a shut bedroom builds up overnight, what else can feel stuffy, and how to tell which one you have.
What a CO2 monitor can (and can't) tell you about your home
4 minA CO2 monitor shows how much outside air reaches an occupied room, but it can't measure every pollutant, test for mold or tell you about your health.
What happens to bedroom air while you sleep
4 minWith the door and window shut, bedroom CO2 usually climbs through the night and levels off near morning, and a few simple things shape that curve.
Why 800 ppm? The bedroom CO2 goal, and where 1,000 comes in
6 minAim for 800 ppm or less, on average, while you sleep. Where that goal comes from, why 1,000 marks the line, and why HouseExhale scores the average.
Bedroom CO2 and sleep: what the research shows, and what it doesn't
7 minThe studies behind the 800 ppm bedroom goal, in plain language: who slept where, what changed, what was measured, and how far the results go.
Bedroom CO2: questions and answers
7 minWhat CO2 level a bedroom should be at night, why the goal is 800 ppm, whether 1,000 is dangerous, average vs. peak, monitors, and how to get there.
Air purifier or fresh air? What each one does for a stuffy bedroom
4 minA purifier cleans the air already in the room. It doesn't bring outside air in, so it can't lower the CO2 that builds up overnight. When you want each.
CO alarm vs CO2 monitor: two gases, two different jobs
4 minCarbon monoxide (CO) is a poison you need an alarm for. Carbon dioxide (CO2) shows how much fresh air a room gets. Neither device does the other's job.
Measuring
Placing a monitor and running a fair check.
Where to put your CO2 monitor in a bedroom
4 minPut your CO2 monitor at head height, away from faces, drafts and sun, in the same spot every night, and check it against outdoor air first.
How to run a fair three-night bedroom air check
4 minMeasure ordinary nights, keep the setup the same, note anything different, and let three nights turn a single clue into a pattern.
Already own an Aranet4 or SwitchBot? Turn the numbers into an answer
4 minHow to turn the chart in your Aranet4, SwitchBot or other true-CO2 monitor's app into a clear answer about your bedroom.
Can I trust my CO2 monitor? Four checks that take one evening
5 minHow accurate home CO2 monitors are, why two of them disagree, and a quick outdoor check that tells you whether yours is close enough for a bedroom.
Free fixes
Changes to try for a night before buying anything.
Free fixes to try before you buy anything
5 minThree one-night experiments to try first: an open door, the fan or ventilation you already have, or a cracked window, and how to read the result.
Sleeping with the door closed: how to keep the air fresh anyway
5 minFire-safety researchers say close the bedroom door. Here's how to get outside air into a closed bedroom anyway, and how to check it worked.
Ventilation systems
HRVs, ERVs and why tight homes need a plan.
Do I need an ERV? How to tell before anyone quotes you
6 minAn ERV fixes one problem: too little outside air reaching rooms with the doors shut. Measure your bedrooms, try what you have, and you'll know in a week.
Getting a bedroom to 800 ppm: how much fresh air it takes
6 minAbout 17 cfm of outdoor air per sleeper keeps a bedroom near the 800 ppm goal. What that means for doors, fans and ventilation systems, and what to ask an installer.
HRV vs ERV: which one fits your home?
5 minAn HRV moves heat between fresh and stale air; an ERV moves heat and some moisture. How your climate and household shape the choice.
Why tight and new homes need a planned way to breathe
4 minAir sealing saves energy but cuts the accidental fresh air older homes got. Why tight homes need planned ventilation, and a simple way to check yours.
Quotes and install
Comparing quotes, the install, and proving it worked.
How to compare HRV and ERV installer quotes
5 minGet two or three written quotes and check each against the same eight items, so you compare the same job, not just the total price.
What drives the cost of an HRV or ERV install
5 minThe ductwork, access, and repairs around an HRV or ERV usually shape the price more than the unit itself. What moves the number, and why.
After the install: proving it worked and keeping it working
5 minWhat to collect on install day, how to recheck your bedroom air after an HRV or ERV goes in, and the simple upkeep that keeps it working.