Geiger Plus Personal Carbon Monoxide Monitor

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Part# 10-07477


GEIGER PLUS Personal Carbon Monoxide Monitor

Geiger PLUS is a key fob-sized unit that provides real time aural alarm when carbon monoxide levels are dangerously high. The unit provides a very loud distinctive alarm at ~41 PPM and an even more annoying alarm at 100 PPM.

The product also detects Volatile Organic Compounds, such as gasoline.

In contrast to competitive products, GEIGER PLUS is much smaller, more responsive and rechargeable. It is designed to run off of an internal USB rechargeable battery.

Geiger PLUS is designed to be attached to a keychain, but because of its small size, it can be hung anywhere. According to our market research, this is the smallest, most portable, most usable CO monitor available, and it is reasonably priced.

    This updated version of the predecessor product (Geiger CO) has exciting new and compelling features:
  • It comes to life much more quickly and may be turned on even in poisoned air, without requiring a startup in clean air.
  • The calibration point is digitally aligned with each unit at the factory, for a baseline of zero PPM, and is also calibrated for 100 PPM.
  • The LED scale is engineered to FAA guidelines for strength of CO and color coding thereof. For reference, see Carbon Monoxide, a Deadly Menace (
  • This new design advises of the possible presence of Volatile Organic Compounds (including exhaust and gasoline vapor) via a distinct, blue LED.
  • The aural alarm starts at ~41PPM and changes to a more insistent tone at 100PPM.
  • The rechargeable battery gives ~6 hours of operation along with a 30-minute recharge time from any USB port (to 80% of charge).
California Prop 65 Warning Symbol

WARNING: Cancer and Reproductive Harm -

How To Use

  • Turn the unit on, unit will auto-calibrate every time
  • Unit monitors air
  • When CO levels rise, LEDs show change and alarm sounds
  • Power or charge via USB

Technical Details

  • Engineered with consideration of published FAA CO guidelines
  • Also provides differentiated Volatile Organic Compound detection. VOCs are often found in exhaust gas.
  • Rechargeable via USB, never change a battery.
  • Factory Recalibration is available ($70; recommended annually, includes new battery.)
  • Size is 1.2 x 2.0 x 0.3″ (3 x 5 x 0.75 cm)
  • Runs for ~6 hours on a single charge
  • Aural alarm sounds at approximately ~41 ppm and becomes more insistent at 100 ppm
  • Shows at a glance through easy to read, color coded LED scale green / yellow / red
  • Hangs anywhere using keychain opening
  • Solid aluminum case in brilliant orange


Ive been happy about this device since it was first announced. I got one of the early versions. The documentation, functionality and size all make it great to work with. I was one of the unfortunate ones who had the back fall off, which I then lost before I could glue it back together. I reached out to the company and they took exceptionally good care of me! Outstanding customer service with every interaction is as important to me as product quality. Im a huge fan!

Peter A
October 18, 2022

I bought my unit back early when it was offered only directly from the manufacturer. This detector is nothing short of fabulous. I fly in a rented Piper PA28-161 ( Warrior II) and the classic black bot panel mounted adhesive detector probably for all I know has not been changed since the plane was built in the early Reagan Administration. No one seems to know the installation date of the black dot detector, and the print has faded so badly that if any sort of date was ever marked, its been sun bleached to oblivion. Again, it is a rental at a flight school. I would recommend this unit particularly for renters. People who own their own plane perhaps can install more sophisticated panel mounted detectors. For scrub hobo renters like me, this unit is perfect. I have it on a lanyard along with my laminated checklists. The unit is also handy when at home or in hotels. Its extreme portability means it can be used in many places. The manufacturer of this device also has a lot of expertise in manufacturing light weight avionics for experimental aircraft. This unit is very rugged and well built. Two other posts have reported supposed premature alarms. Perhaps the units are indeed just doing their job and immediately signaling a 50ppm CO level, transient though it may be. Ive had my unit for about a year and it has gone off twice under circumstances that seemed reasonable. Again... highly recommended. especially for renters.

Paul S
October 28, 2021

Okay, I hate giving less than stellar ratings but monitor falls a bit short.. Not by letting the gas get to you, but by freaking out when any CO even thinks about coming around or any volital organic compound. Its just too sensitive. I have worked inthe chemical industry for the past 30 years. If you have an alarm set point set too sensitive, it alarms too frequently and becomes a nuisance alarm. If you let it chrip on you learn to block it out theyou start to tune out other alarms. This sets up a bad normalized deviation where you start blocking out warning signs. Please figure out how to make it not so twitchy and it will be a great unit. Gonna head Back to my yellow 2year unit.

Charles R
January 22, 2022

Case comes apart in your pocket. Nothing holds it together except the snug fit between the case and the cover. 6 months old and no external signs of abuse. The circuit board just falls right out. Not a good sign for an aviation safety device. Also did not come with a charging cord. Bought at the initial price of $99.99. Aviation is expensive...but come on boys, I expect better than that.

Jeffrey A
December 12, 2021

I had same result as another reviewer. Calibrated it in clean air, flew the airplane and then on landing got an aural alert. Re-calibrated in clean air once again, went on another flight with two other CO detectors onboard. Same result, on landing got an aural alarm and LED indicating above 50ppm. Both other detectors meanwhile showed clean air in the cockpit. I cant rely on it and even the documentation it comes with implies that its more of a toy than anything else.

Paul R
October 19, 2021

Purchased the monitor at the same time as I replaced the muffler on my 185. It sounded the alarm on my first flight and after a several hours checking the muffler, I checked the monitor and found that it was defective. Ive seen a few similar stories for this monitor so Im going back to the cards.

Gregory E Verified Purchase


March 28, 2024


Please note, Aircraft Spruce's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Aircraft Spruce assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: Is the alarm sound loud enough to be heard in a flying aircraft for a pilot wearing a noise cancelling headsets?

Per the manufacturer, there is no specific data that tells us yes or no. It will need to be tested in the specific environment.

Q: Does this unit display the level of CO in the cockpit? Are there any markings on LED scale or any digital display?

As the CO rises more LEDs will light up.

Q: Does the Geiger CO Carbon Monoxide detector only come in one color?

Yes, this is now available only in black. We used to ship the units out in orange, but due to supply issues on the orange material it was changed to black casing.

Q: What is the lifespan of the sensor for the Geiger CO monitor?

There is not a specified lifespan for the sensor per the manufacturer.

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