MotteruMini CO2 Detector with Alarm - Air Quality Monitor, Carbon Dioxide Detector Battery Powered with LED Digital Display and Sound Alert, Portable co2 Monitor, Air Quality Tester, CO Detector

So let's get this out of the way: this is not as accurate as an Aranet CO2 meter. But, for a much smaller fraction of the price, I've found it to be consistent as to how much it tracks off of my Aranet, so I have definitely found use for it.I'm one of those people at high-risk for bad results with COVID, so I have had to take it more seriously than most. When public health professionals focusing on air quality noted that CO2 readings are a good proxy for having an environment with lots of fresh air circulating, I bought an Aranet reader. However, at $250, they are pricey. When I brought it places to check out CO2 readings, I was always afraid of losing it or damaging the screen in my bag. But a lot of the smaller meters like this are wildly off, or they come with very noisy alerts that you can't turn off.This meter, however, I've been pleased with. The first week or so I had it, I hung it near my Aranet - the displayed readings were consistently between 100-150 ppm less. I re-calibrated it, and the readings stayed in that same range, so when I look at it, I mentally add 125 ppm. Looking at other reviews, other monitors have had different results, so I would say if you're concerned about absolute precision, you will want to compare it against a more reliable CO2 meter. (The first C02 monitor I ever bought is wildly inconsistent and I basically use it solely as an indoor thermometer and humidity meter at this point.)Also, you can turn off the alert on this machine - once it boots up, a quick double-tap of the button turns it off. But if you choose to keep the alert on, it is definitely loud and sharp enough to get your attention!I now clip this to my bag when I'm running errands, which has been really informative - I now know which particular grocery stores and pharmacies have better air quality in my area, which helps me feel a bit safer when I shop. But I also took it to my State Fair, and to a wedding in a historic house.At the State Fair, there was one location where we wanted to eat in a dining hall - the meter let me know that deep inside the hall, the air quality wasn't as good as near the large open doors, so we sat near them instead and felt safer taking off masks to eat. And there was another display building where there weren't many doors at all, so the CO2 shot up rapidly, letting me know I probably shouldn't hang out there too long.At the wedding - which was held in a historic house - I had no problems discretely checking the meter to confirm that the air wasn't circulating well inside, so we sat outside at the provided tables on the porch, and just put on our masks to go inside for the ceremony, or to go inside get food and drinks. (And this was where being able to turn off the alarm really came in handy!)Another commenter noted the screen turned off after a minute or so - this is true, but that's because unlike an Aranet or other monitor that is fully battery powered, this has a rechargeable battery. The screen won't stay lit the whole time to conserve battery, but I have heard it "ping" at me if the numbers go up and the screen is off. So it's working, it's just not a constantly viewable screen. But all you have to do is tap the button and it comes right up. Also, I've found it to be pretty quick to take a charge, so it's not too difficult to keep it topped up if you keep a charger cord with you.I've found the screen to be nicely legible - when it's on, it's really got very bright readings - and the color code along the bottom is easy enough to read as well. Re-calibrating it is not overly intuitive, so I do recommend keeping your documentation. It's just with a single button, it depends a lot of timing and hitting the button in a certain sequence. So not difficult, just not easy to remember.So bottom line, this isn't my primary CO2 reader when I'm really concerned about precision - that will always be my Aranet. But for travel where you just want solid trends and don't want to worry about losing a more expensive reader? Sure, this is great. I actually ordered a second one because I don't know how long things like this will be on the market, but for someone like me, knowing the CO2 readings is going to be helpful for traveling for many years to come. Essentially, when you see the numbers rocket up to 1,500+, a relatively small ppm difference doesn't matter: you know it's not a great environment and to keep your mask on. This little machine tells you that information clearly in a compact form factor and a decent price point.

It’s hard to tell if it’s on or not. It didn’t come with any instructions.

This device works well when it works, but you can't even get a whole days use from one charge. I have found that very frustrating.

This is great for short trips or an evening out. But the battery life is not good. So if you’re taking a long flight/trip or wanting for kids are school, etc… yeah it lasts maybe 8 hours on a charge. Not that great. But it is nice to spot check say — what’s the air quality in my dentist office while I’m laying there mouth open. It’s cute and pocket sized. But definitely looking for a longer lasting option already.

Nice compact design. Seems to be very accurate, tested in poorly ventilated meeting rooms and measured up to 2600. Also blew some smoke from a burning match over the unit and git an alarm immediately. The alarm is not too loud and can be turned off, which is really nice when in Church or in a meeting room. Unit goes in sleep mode to safe battery life.

I used this at work Incase the air became over loaded with co2.

The detector seems to be accurate enough. I never had to manually calibrate it. It's a bit annoying that you can't control or silence the beeping. But the biggest flaw is the battery life. It lasts at most for a day on a full charge.

Aa Airbnb users and hearing of CO2 issues at Airbnb we wanted to protect ourselves when we stay at an Airbnb.