---
title: I Took a Radiation Detector on a Plane. Here's What It Actually Read - Whiskey Alpha Pilot
description: A Radiacode 101 on a commercial flight: 0.05 microsieverts on the ground, 1.02 at FL350. Twenty times more, and why that matters to crew not passengers.
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I like things that go beep. Any gadget that screams like a demented beetle when it finds something interesting was always going to end up in my bag, and that is honestly the whole reason I own a Radiacode 101. The problem with owning a radiation detector is that you run out of things to point it at rather quickly. There are only so many times you can test a smoke detector, particularly as modern ones generally don't contain a radioactive source anymore. So it came with me on a commercial flight, and sat on a tray table at 35,000 feet reading twenty times what my kitchen does.

![radiacode 101 scintillation dosimeter](https://whiskeyalphapilot.com/images/logbook/radiacode/radiacode-101scintillation-dosimeter.png)I originally found the Radiacode through [Radioactive Drew](https://www.youtube.com/@RadioactiveDrew), who has been pointing radiation detectors at things for a while and is therefore partly responsible for my interest.

Before any of the flying, I did try the obvious thing. There is an [atomic testing museum in Las Vegas](https://www.atomicmuseum.vegas/), and I walked round it with a radiation detector in my pocket like a man who had planned this brilliantly. It was a disappointment on two counts. The readings were far less exciting than the subject matter deserved, and they said no filming in the really interesting parts. So I have no footage of the least interesting radiation survey ever conducted.

Which is how a device bought for one purpose ended up doing its actual job on an airliner.

## A note on carrying one onto a commercial aircraft

The Radiacode 101 is small, but it has a screen and flashing LEDs, and when it decides something is worth flagging everything lights up red and the thing starts making a noise. On a kitchen table this is entertaining. In a packed airbus, surrounded by strangers, it is a slightly different proposition.

It also has to get on board, So like all good carry-on bags it went through the X-ray machine at security, still switched on and still recording, which produced results I will come back to.

Once on board I asked the crew before I started waving it about. This got me a couple of odd looks, an introduction to my website, and a fairly long conversation about why I fly a 172 rather than a 737, but they let me get on with it. Nobody called anyone in authority. So my advice is always ask first. It costs nothing and it is a great deal better than the alternative version.

## What the thing actually is

The Radiacode 101 is a pocket scintillation detector. It gives you a live dose rate, can log to an app, and produces enough graphs to keep a curious person occupied for a whole flight or two. It is not aviation kit and does not pretend to be but it is an effective gadget for people like me who are simply curious.

This is not a product review.

## Background first, or none of it means anything

Everybody is being irradiated all the time. That is not a dramatic claim, it is just the world we live in. Rocks, soil, the sky, the food you eat, and to a small extent you all contribute to the background radiation we are living in.

It also varies enormously by where you happen to live. Parts of Cornwall and Aberdeen in the UK sit on granite, and granite contains naturally occurring uranium and thorium, which decay into radon. People in those areas live with background levels well above the UK average and always have, in houses built from the local rock. It is known, it is measured, and nobody is being evacuated.

I mention it because there is no zero when it comes to radiation exposure. There is only more or less than the background you already live in.

For me, at home on the kitchen table, the Radiacode 101 reads 0.05 µSv/h.

## In the air

At cruise, at FL350, it settled at 1.02 µSv/h.

Twenty times the ground reading.

I sat and looked at that for a while. Twenty times is not subtle. There was no spike, no drama, no demented beetle screaming 'we are all going to die' - (I turned the sound off). The levels climbed steadily as we went up, then sat there for the whole cruise, and dropped back down on descent.

Which is exactly what my A Level physics said should happen. There is less atmosphere above you and thus less shielding. It was still oddly satisfying watching it go up and down live on a tray table, particularly on a flight with no seatback screens, where the detector was the only thing on board with a display. The altitude reading came from SkyDemon, because of course I had SkyDemon running as a passenger - don't you?

## Twenty times what, though

![Cartoon Chest X-Ray](https://whiskeyalphapilot.com/images/logbook/radiacode/chest-xray.jpg)A chest X-ray is typically about 20 microsieverts. I said typically. they can be considerable more depending on the technique and equipment.

So a local European flight, London to Barcelona, cruise and all, comes to roughly a tenth of a chest X-ray. A transatlantic crossing is about two. That is the entire passenger story. You will not feel it and you should not be thinking about it.

But now run the same numbers for someone who does it for a living. Long-haul aircrew could accumulate somewhere between 100 and 250 chest X-rays a year. One measured flight-attendant career came out at around 1,500. Before you quote flight hours limits at 900 or 1000 hours a year, I would point out that you still accumilate the exposure during rest breaks, or in the jump seat, and the numbers increase the higher and closer to the poles you fly. It's a complex subject which is why cosmic radiation is treated as an occupational matter for aircrew rather than a passenger safety issue. The difference is not the rate, it is the exposure time multiplied by a career in the sky.

## Yes, This is already regulated

UK operators have been legally required to assess crew cosmic radiation exposure since the [Air Navigation (Cosmic Radiation) Order 2019](https://www.legislation.gov.uk/uksi/2019/1115). UK aircrew exposure is assessed, recorded and managed. This is not an unwatched problem that a man with a gadget has just discovered.

I am not going to attempt a summary of the regulations, because I am a PPL with a gadget and a YouTube Channel. If you want them, you can wade through the legal jargon on the link.

## An aside about that trip through security

![Pilot trying not to let the Xray machine explode](https://whiskeyalphapilot.com/images/logbook/radiacode/pilot_xray_machine.jpg)So, back to the airport X-ray machine.

It saturated. Flat top on the graph at 15,000 µSv/h, twice, which means the actual peak was higher than the device could measure. I do not know what the real number was and neither does the Radiacode. I also have no intention of finding out, because searching for the technical specifications of airport security scanners is not something I particularly want sitting in my search history.

Before anyone panics: that is a rate, not a dose. The pulse lasts a fraction of a second, so the total absorbed is small. But it is a genuinely serious piece of equipment doing a genuinely serious thing, and it is worth understanding the difference between the machine your bag goes through and the one you walk through. The scanners passengers walk through are millimetre-wave, which is non-ionising. Different technology entirely.

There is more on this in the video, because watching the graph clip is better than reading about it.

## Where does that leave general aviation

![Cartoon Cessna with a Mk 1v Radiation detector slung underneath ](https://whiskeyalphapilot.com/images/logbook/radiacode/radico_cessna.jpg)Almost entirely out of it, is the honest answer.

I fly a 1977 Cessna at a few thousand feet. Whatever happens at FL350 is not happening to me, KK does not have the legs for it, and my flights are measured in hours rather than careers. Every number here comes from a commercial flight. I have not yet taken the detector up in a light aircraft to see what it reads down where I actually operate.

## A word about the internet

There is a genre of content that will take a number like twenty times and add it to radiation and then run straight at the panic button. Go looking and you will find people selling you protection from all of it, up to and including the lead-lined option that keeps appearing on my feed, especially since I started researching this article.

You do not need to buy more tinfoil just yet.

The numbers are real. The occupational concern for aircrew is real and documented. The idea that a fortnight abroad or two hours in a commercial jet requires personal protective equipment is not, and anyone selling you that is selling you something. Unless it is sunscreen for the beach - you can never have too much sunscreen.

## Was it worth buying

For me, yes, and let us be honest about why. Not because it warned me of anything, because it did not. It satisfied my curiosity, and if I ever get into collecting WW2 aircraft instruments it will come in useful - because they are loaded with radium. But I now know a number I did not know before, and I am the sort of person who wants to know the number.

Lastly no it does not live in my flight bag. I am not quite that geeky, and there is a limit to how much kit I will carry. But I will take it up when I remember, assuming I have charged it, If it ever tells me anything interesting at circuit height, you will hear about it. I suspect it will be the most boring graph I have ever produced.

One last thing, and I mean this. Don't climb into an X-ray machine just to make a video. They will not be pleased.

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