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Part# 11-17141
MFR Model# ASCO401


The Aithre Shield 4.0 auto-pairs to your iOS device using the free Aithre Connect app. Readings are collected and graphed in the background and Siri notifies you via your iOS-paired headset when thresholds are crossed. In addition to the app, the Aithre Shield 4.0 itself also has a glowing light indication of the CO levels and an alarm that is triggered at 50 ppm. The Shield 4.0 portable detector is sensitive and responsive at the lowest levels of CO gas between 0 and 255 ppm to detect and manage CO before it becomes an emergency. With no recalibration required for 10 years, youll enjoy many years of safe flying with the Aithre Shield 4.0.


Under 30 second sensor response between 0 - 255 ppm with 1 ppm resolution

iOS: Aithre Connect App integrated, providing trend data plus popup and Siri notifications to your headset (when paired) when threshold CO levels are crossed.
Click Here for the Apple App Store for Aithre Connect

Temperature Independent:
Internal temperature adjustment circuit that compensates for temperature induced errors in the sensor between -10 C to +50 C

Measures just 2 inches tall and weighs about an ounce

No Recalibration:
State-of-the-art sensor requires no recalibration for 10 years under normal operating conditions

Pressure & Altitude Independent:
The detector is not affected by pressure and altitude changes

Includes a custom charger that duals as a mount and that allows charging during use via USB.

Clip Mounted:
Includes 2 custom clips for easy mounting in various locations like your aircraft and hangar

Every Aithre detector is individually calibrated using high precision calibration CO gas and comes with a signed certificate of calibration


  • Dimensions: 2 inches tall
  • Weight: About an ounce
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I was having trouble charging and using my Aithre shield CO detector. I called and spoke to Susanna and Jim and found them to be extremely helpful and knowledgeable. They took a genuine interest in helping me to understand the CO monitor and the app. use. Jim also took time to explain the causes of various CO levels during run up and flight. He was very helpful. Itâs wonderful to see your company with such knowledgeable employees and who backs up their products the way Aithre does.

January 19, 2021

Well worth the cost for the peace of mind provided. The highest rating my PA24-250 had was 20ppm going around in circles on a compass rose setting up my new G5. In flight with the heater on it registered 2ppm. Its surprising how much that knowledge helps. I would definitely recommend this device to anyone that needs a CO detector (and has an Apple iOS device).

Joel W
January 12, 2021

It is simple to use - open the app and turn the unit on, it pairs automatically. The notification it gives through Siri if connected to your headset is vital as you likely wonât be looking at it as carbon monoxide fills your cabin. The app graphs altitude and temperature against the CO level, quite nice. In my plane it registers if the window is open while taxiing, I never knew!

Clint H
March 14, 2020

Great product with superb customer service from Aithre. Portable unit also syncs with your phone/tablet through an app. First CO detector Iâve seen with such a long-term calibration guarantee.

Kris O
March 14, 2019

I ordered the Aithre Sheild back in mid May just to be on the safe side since I had CO problems prior to my engine rebuild last fall. Its now late June and I am just getting around to trying it out. I can say Im disappointed. Most detectors will show you the reading on the devices face. While I was concerned that the Aithre didnt have that ability, I figured I would simply link it to my IPad when I fly, and use the app. The manufacture also claimed the color indication on the large A in the front was easy to see if your not using the app. When I purchased the Aithre I figured using the app with my IPad would be acceptable since I use my IPad with every flight of my C172K for ForeFlight. I traditionally link the Foreflight to my Garmin GTX345 transponder and PMA8000 audio panel for audio alerts during each flight via BlueTooth. This setup has worked excellent since both the audio panel and transponder were installed last year. Unfortunately once I turn on the Aithre and open the app on my IPad, it automatically disconnects my PMA8000 Bluetooth audio connection from my IPad each and every time. This means I either have to give up the audio connection or give up the CO monitoring app and without the Aithre app I cant see any CO data, and the A indicator on the face isnt that great to try and see when it is sunny. Night time it is very visible, but i dont typically fly at night so its no help for me in that aspect. You can get the connection of both to work at first if you connect the Aithre first and then connect the PMA8000 Bluetooth connection, but after a few minutes the Aithre connection wins and the Bluetooth connection to the PMA quits. I also connect my IPhone to my Bose headset to be able to make calls once in a while. While the phone is connected I use it to play music on Pandora. To avoid the mess of the connection on the IPad I gave a shot to connecting my IPhone to the Bose headset via Bluetooth while playing Pandora and the Aithre app. Guess what...the Aithre kicked out any music or phone ability and did its thing. Seems odd the manufactures didnt notice this obvious issue since it happens on so many devices. God forbid you use your phone for anything except the Aithre. The third alternative to make this meet your expectations is to tediously switch back and forth and reconnect each time you want to check the CO levels. To me this means more attention is spent in the cockpit than out, which can have its own set of problems at times. It is probably too late for me to be able to return this, so shame on me for not trying it out when I first got it. Do yourself a favor and spend your $130 on a detector that has a level indicator on the face and avoid this one. It just wont work out the way you think it will.

Gil G
June 25, 2020


Q: Says experimental, but if you own a small GA aircraft, that does not require C02 monitoring, would you net be allowed to install...for say situational awareness? Just trying to upgrade from the little card and not spend a fortune

Yes, this can be utilized in both certified and experimental aircraft as it is a portable unit and not for permanent installation.

Q: Can I print the graph of the CO levels?

Ask of now you can screen capture from the app and print that. They are working on an upgrade to the app that would allow for export to a spreadsheet.

Q: How long does the battery last between charging?

Roughly 12 hours.

Q: Is there a temperature limitation? Only works within a range?

Per the installation manual, this has a range detection of 0-255ppm and normal temperatures for in-use are -14F to 122F.

Q: Is their an Android version? or compatible app?

Per the manufacturer, it is only compatible with the IOS devices.

Q: Will you get an alert sound from the device if youre not using the app?

Yes, without the app the light indicates the levels of CO. Additionally at 50 ppm and above there is an audible alarm. Every 2 minutes for every 50 ppm increment. ie at 100 ppm you will get 2 loud beeps every 2 minutes.

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