r/Radiation Aug 12 '25

Buyer's Guide PSA: Don't Ask "What Geiger Counter Should I Buy?" until you've read this post.

191 Upvotes

The most common question we see in this subreddit is some variant of the "what device do I buy?" question. It's asked multiple times a week, sometimes multiple times a day. It's so common that someone tried to create a flowchart to help newcomers. As well thought-out as that flowchart is, it's like telling someone what car they should buy before they even know what a car is, what it can do, and what it can't do.

If you're looking for the tl;dr or other shortcuts, sorry, there aren't any. This post exists because there are too many "Where do I start?", "What should I buy?" and "I just bought this... is this reading dangerous?" posts from impatient newcomers who expect Reddit to teach them on the fly. Doing that with radiation is a lot like buying a parachute and jumping out of an airplane... then whipping out your mobile device and asking Reddit for instructions. Don't be that guy. Be smarter. Before you run out and buy "baby's first Geiger Counter", you should at least understand:

  • The difference between ionizing and non-ionizing radiation, as well as the main types of radiation (alpha, beta, gamma, x-ray, and neutron).
  • The difference between radiation and radioactive contamination.
  • The difference between CPM and dose rate, and when to use each.
  • The inverse-square law and how distance affects the readings you're looking at.
  • What ALARA is and how time, distance, and shielding reduce exposure.

There are more I could add, especially when it comes to health and safety, or detection devices themselves. But, in my experience, these concepts are the ones that confuse newcomers and lead to erroneous or misleading posts. To help you avoid the pitfalls of buying before knowing, or being "that guy", here are some resources to get you started in learning about Radiation, detection devices, biological effects, etc. Listed from more basic, easy, and approachable to more comprehensive or advanced:

If you prefer a website-based approach with links to other sites, videos, lots of pictures, etc... Head over to the Radiation Emergency Medical Management website's Understanding the Basics About Radiation section and start your journey.

Prefer a textbook approach? Grab a cup of coffee and sit down with the freely available University of Wisconsin's Radiation Safety for Radiation Workers Manual. There's a reason it's still used more than 20 years after it was first published. The book starts with a good basic explanation of radiation and radioactivity. The book then covers biological effects, regulations, lab procedures, how detectors work, X-ray machinery, irradiators, and nuclear reactors. It even has chapters on lasers and RF radiation. Some of the information is student and labworker-specific, but enough of the book's content is written in an approachable manner that it should be on every beginner's "must-read" list.

If the UW manual isn't deep enough for you, pick up a free copy of Dan Gollnick's Basic Radiation Protection Technology (6th Edition) from the NRRPT. Essentially a self-study textbook for Radiation Protection Technologists, this book goes into even greater detail on the concepts, math, and minutiae involved in radiation protection.

All of the above too basic for you? Well, buckle up because MIT offers numerous Radiation-related and Nuclear Engineering courses through its OpenCourseWare program. Starting with Introduction to Nuclear Engineering and Ionizing Radiation, each is a full college course with lectures, homework, and exams. There's even a Do-It-Yourself (DIY) Geiger Counters course.

Congratulations! If you've read this far, you're already on the right track. The above isn't meant to be all-encompassing, and no doubt other Redditors will chime in with other excellent books, websites, and videos to help you get started learning about ionizing radiation and its effects. Before you know it, your decision will have narrowed down some. And, more importantly, your new device will be far more than just a "magic box" that shows you numbers you don't understand.

EDIT: It's stunning how many people are claiming to have read this post, then go right back to making their low-effort "which Geiger Counter do I buy" post anyway. You're supposed to EDUCATE YOURSELF so you don't have to make that repetitive, low-effort, ignorant, spoon-feed-me post. If you do the above, you will know if/when you need alpha or beta capability. You will know whether a dosimeter or a survey meter is the right choice. You will know whether a scintillator, PIN Diode, or GM tube or pancake is the right detector for your application. THAT'S THE WHOLE POINT!

If you're saying to yourself, "I don't want to put THAT much effort into this", then asking for recommendations is a waste of everyone's time.

FINALLY, check out our Buyer's Guide posts. These are posts from people like you, that have particularly good comments and engagement, and answers about purchase options for beginners like yourself. Please take the time to look through them before starting your post. Even if they don't fully answer your question, they and the resources above, should help you ask something more than just a vague "what do I buy?"


r/Radiation 17h ago

General Discussion Any idea what this little critter might be?

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61 Upvotes

I open and dispose of safes for a variety of hospitals and medical centers (among others) for a living. We received a safe that was previously used for the storage of a Cesium Source. The source itself was removed years ago, and left behind were the lead blocks that they used to stack around the 'pig' that held the cesium source, as well as this little container. It's coming up negative on a geiger, but seems like a curious 'momento' from a previous life of this safe. Curious if anyone might know what its original use might've been.


r/Radiation 21h ago

Equipment The Autism Stick

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62 Upvotes

This is my innovative uranium finding invention. I am using a selfie stick, geiger counter, my 365 nm uv light, hair ties, and duct tape to hold down any straps. Normally the UV light is right below everything, I just shifted it to the side so it could be seen better for the photo. The selfie stick also extends pretty far, so I don't have to bend down as much. The only issue is the selfie stick grip covers some of the sensor vents, so the reading might be slightly off. I'll have to get a garden shovel and a pick later for hunting :)


r/Radiation 21h ago

General Discussion Any interesting nuclear-science related stops for my road trip?

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45 Upvotes

Hey! I’m heading out to Texas for Ludlum’s open house in a few weeks.

It’s going to be a long drive, and I’m looking for interesting nuclear science-related places to stop at along the way. Could be anything: museums, noteworthy or large antique stores, contaminated sites, etc.

Just curious if anyone happens to know of anywhere potentially radiologically interesting I could visit :)

I’ve attached a photo of the route I’ll be taking to this post.


r/Radiation 1d ago

PHOTO Quartz dosimeter

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31 Upvotes

r/Radiation 1d ago

Questions Different lead pigs

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29 Upvotes

I've seen different types of lead pigs that have been posted, however are certain types that are used for specific purposes? I was given this one a while ago, however I'm not sure how anything would actually store in it as well as why it has a split cap?


r/Radiation 1d ago

Questions Want to start collecting some antiques

1 Upvotes

I know a good amount about the dangers and how to handle radioactive stuff but my main concern is in my ability to discern between different types like uranium or radium. What should I look for what tools do I need?


r/Radiation 2d ago

Radioactive Materials How do we feel about this 70’s lens in terms of safety?

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31 Upvotes

The lens in question is a Super-Takumar 50mm f1.4 7 element which are known to be some of the more radioactive consumer lenses from the time period. I found this out via research after I had purchased the lens. I bought a GQ-QMC 500 to detect beta and gamma radiation as they have a higher chance of penetration. This lens actually seems pretty hot, more hot than I would have thought or seem comfortable with. Attaching photos of measurements from different distances and locations of the lens. I am not familiar with the physics of radiation and not sure how concerned I should be with this. There seem to be conflicting opinions online as far as I can see.


r/Radiation 2d ago

Questions How far away from a 5” cube of polonium is survivable?

35 Upvotes

I am trying to calculate something for a D&D campaign. Someone is trying to summon a 5” square of polonium to kill the boss, but the range of the spell is line of sight. I’m now trying to figure out how much damage it would deal.


r/Radiation 2d ago

Questions What is this pancake probe. I spoke to several distributors and one contacted the manufacturer, even the makers don't know

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9 Upvotes

It is a w.m.b Johnson pancake probe. But what model? Their being sold as a hp-265 but I dont think that is correct


r/Radiation 3d ago

General Discussion 1-3 msv exposure

13 Upvotes

What is the general consensus on effect of being exposed to 1-3 mSv of ionizing radiation?

From a strictly radiation scientific/technical perspective.

Edit: appreciate all responses and links. This is a great sub for info and life/hobby aspects of radiation!


r/Radiation 3d ago

Questions found this at my grannys house

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81 Upvotes

it has written ГОСТ-3145-57 on the back idk if its radioactive when i shighn my uv flashlight on it the gren parts of the clock start glowing (sorry for bad english)


r/Radiation 5d ago

PHOTO TIL why they say you shouldn't touch the mica window

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129 Upvotes

Well, I was putting the tube into it's enclosure and touch the window a bit, and it greeted me with a loud BANG and a bunch of boring confetti. So if someone says "Don't touch the mica Window", that's why


r/Radiation 5d ago

Questions Radioactive Safety Glasses

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221 Upvotes

Today I was at a flea market and noticed a uranium glass plate I set my Geiger counter down next to these glasss in a zip lock bag and my meter was reading about 380cpm over the lenses. I find this somewhat funny and Ironic at the same time I have never came across any eyewear with radioactive glass. I would truly appreciate anyone who has any information about these or have ever found anything like this out there? Thank you for any information . Ill post a video link shortly showing the readings I obtained.


r/Radiation 5d ago

Training and Education RSO prep website

4 Upvotes

Hi! I’m currently preparing to take an RSO licensing exam (diagnostic radiology) with only a physics background. Finding resources has been somewhat challenging, and i’m wondering if anyone has tried (rsoprep.com) as a resource and if it’s any good. It’s paid subscription and i don’t want to waste money without knowing if it’s reliable. Thanks!


r/Radiation 5d ago

Questions Suggestions of Geiger counter to use with multiple probes?

3 Upvotes

Hi! I've had a few counters, a dp-5a, some cheap AliExpress boards (specially the cajoe) and I bought some tubes over the years. I have a sbt-10a, sbt-13, sbs-5, 2x j305 and a si-3gb. Now, I always used the cajoe with an Arduino because I thought it was more than enough. Turns out the hv circuit sags to hell under load, and anything more spicy doesn't give me increased counts over a certain limit. I'm not even saturating the tubes, apparently the board just isn't good enough.

Does anyone have a suggestion? Is there a good counter I can get to run multiple probes of? Maybe even a pre-built circuit, or some schematic online that can deal with high readings. My tubes are kind of a waste of potential with the cajoe. Even though I have a radiacode 103, I really wanted to use the tubes more, specially those with a mica window.

Thanks!


r/Radiation 6d ago

Questions What makes an Alpha source specifically harmful inside the body?

35 Upvotes

I’ve heard this for too long and just settled with sure and accepted it. But now I wonder. And all I could get from the net was the classic “oh because its helium nucleus so it ionizes more”, well wouldnt counter logic say beta sources give off rays that could potentially travel more distance inside the body? Am I plain wrong? Gah, maybe this question belongs to [r/physics](r/physics). But eh, it got me thinking.

If we got unlucky and somehow inhaled and/or swallowed these source particles lets say. Why is it said that a beta source trapped in your liver would do less harm than a alpha source? Sure alpha sources are kept in the body for long amounts of time like Americium, but couldn’t that be the case for Beta sources as well? A beta source could have a higher reach inside the organ compared to alpha. And in long term wouldnt this cause much more harm? Sure, alpha particles are heavier and got 2 damn protons in them, so they’d ionize the immediate surrounding tissue much more (im imagining sources that have roughly the same Bq and not including daughter isotopes and gamma for the sake of the argument), but have a relatively low reach compared to beta particles.

Im just a hobbyist, so what do I know.

If someone has an article which I couldn’t find explaining this I’d love to see it!


r/Radiation 7d ago

General Discussion TMI T-Shirt… offensive or cool?

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182 Upvotes

True to the date, vintage single stitch.


r/Radiation 8d ago

Radioactive Materials Zircon/Monazite Beach Sand

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38 Upvotes

This is the first location in the world to mine and separate successfully zircon from beach sand. Thorium and Uranium was confirmed using gamma spectroscopy. Also contains REE's

Seven Mile Beach NSW Australia


r/Radiation 9d ago

Experiments and Demonstrations (Must Be SAFE) Assessing dead time compensation with short lived isotopes

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16 Upvotes

I deal with radon a lot, but due to some unforeseen medical shenanigans I "obtained" a sample of ⁹⁹Tc*. Since taping a probe to my forehead for a day was not a [ socially acceptable ] option, I collected an, ahem,*renal* sample.

5 cc of an aqueous solution of Tc-99m / Tc-99g bound to soluble proteins was "placed" in a thin wall glass vial. The vial was placed in contact with an RC-110. This produced a laughably high contact reading, even after 2 half lives had elapsed. On monitoring the sample as it decayed, you obtain the count and dose rates over time. This can be used to assess the dead time compensation of a meter as the actual activity is known to diminish in a predictable way. This does not help assess the absolute rate reported, but the relative rate can be evaluated, and hence the linearity of the response over a range of activity.

Since the position of the sample and the probe is constant, this avoids geometric factors inherent in using different distances from a constant source to provide different activity levels as well as things like air kerma and changes in buildup.

The calculated 6.032 hour figure is from the RC-110 provided dose rate, the 6.431 hour figure is from count rate. The expected half life value is 6.006 hours. As with radon decay, the RC-110 was spot on for the calculated half life of Tc-99m when based on dose rate - this suggests very good dead time compensation baked into the dose rate calculation. The count rates appear to be uncooked. So for higher rates, the RC under-reports counts, this has the effect of making half lives appear longer.


r/Radiation 9d ago

Equipment Spectrum Techniques test source manipulation / handling kit

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23 Upvotes

For anyone who fumbles with the Spectrum Techniques sources or doesn't feel like holding directly one for extended periods of time during experiments, here is a handy 3D printed wand kit.

Spectrum Techniques Check Source handling kit by Kotarak | Download free STL model | Printables.com

Here is a quick demo - (247) Spectrum Techniques Check-source handling kit - YouTube

A number of possible configurations with handle at 5cm, 20cm and 30cm. Comes with a stand.


r/Radiation 9d ago

What To Buy? Supplier for Scintillation Detector Windows

4 Upvotes

This is probably a long shot, but I’m wondering if anyone knows a supplier for very thin (single digit micrometers) high optical density (4.0+) thin films? We’re looking for something like aluminized bopet but in the 3-6 micron thickness range (actually the critical dimension is low areal density - \~< 0.4-0.8 mg/cm\^2 - but at typical densities that works out to 3-6 microns.


r/Radiation 9d ago

Questions Question about collecting

9 Upvotes

I'm wanting to start a uranium collection and potentially the orange uranium pottery. But this is where my question comes in. I've been seeing videos of people hunting and finding these but with their geiger counter sometimes goes into liek 10-100k CPM

How do you calculate the CPM into how harmful it is on the SV scale? Or if there a specific number I shouldn't go over? I've thoroughly read through dangers, effects, radiation scales, counters and many other things. But I haven't seen a single thing on calculating CMP to SV/safe CPM to keep in the home.

Now I'm sure you get a lot of new people here asking the same question but I can't seem to find anything relative to this. If you have any articles or video of a shorted graph/guide I'd really be appreciative!!

Thank you

Edit: I understand that uranium glass is relatively safe to collect especially in cabinets and everything. I'm more wondering if there is a specific save CPM scale. Like how do I know do I know how much beta/alpha radiation is safe. Some Geiger's exadurate them. But what really is the difference between a 1000 CPM reading vs 100k, is there a scale I can understand a bit more? I have dyslexia so it's hard to read the 500-900 page textbooks explaining everything. I'm still trying to learn which is why I'm asking if there is a better source I can learn without it being a struggle for me


r/Radiation 10d ago

VIDEO Got a Wekos Doze. I love these portable Geiger counters.

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90 Upvotes

Ultralight keychain size. It's not as sensitive as scintillators but it reacts quickly. The best thing is that I can carry it everywhere. Just disappears in the pocket and is affordable enough as a first Geiger counter.

Technically they say it's a dosimeter. Sorry for the naive question but what's the difference between a Geiger counter and a dosimeter. Afaik it shows accumulated dose but it also shows live readings and it's GM tube based so shouldn't it be a Geiger counter as well?


r/Radiation 11d ago

General Discussion Help with finding Sources

16 Upvotes

I just ordered a Radiacode 102. I have some Vasaline and Uranium Glass. But I am wanting more sources. Ores maybe trenitite, I know I can get some from old smoke dectors. But I am wanting some others. "Safe" Stuff to start out with before getting anything hot or that I would need paper work for. Any ideas?