Radiation of lantern mantles

Every now and then the question is aksed: how radioactive is my lantern mantle?

In 2019 I could use a radiation measuring set: FAG Kugelfischer PDR 7001 from the Dutch military.
Now the measuring could begin you think. Well yes and no. Biggest issue is calibrating your set. This set is ex-military and not calibrated for many years now.
I haven't searched yet but my guess is that calibrating a set is expensive ;-)
So I could only measure relative but not absolute.
Relative = measurement can be used to compare between each other.

Also keep in mind that most of these mantles are old. I have them beacuse I get them with lanterns i buy. I don't sell mantles nor do I know shop that do. If you are looking for mantles to buy, look around in your neighbourhood, country, who sells pressure lanterns and ask if they sell mantles too.

Used set:
I could use a ex military radiation device, the IM-7001 of Kugelfischer. This device measures in the radiation units Gray.
This device has a build in Gamma detector which makes it easy to keep teh measurements consitent as to distance and place.
On the device there is a mark (yellow dot) which indicates to Gamma detector.

Stralingsmeter PDR 7000 - www.petromax.nl
The used set: FAG Kugelfischer IM-7001 from the Dutch military. Next calibration date july 1994.

What units should be used?
Radiation units are or can be confusing because there is a difference between radiation being emitted and radiation being received.
Since the new standart is Gray (Gy) and my device had these units I did not convert the units.

I did found a conversion site: convert-me.com, if you want to convert or compare your own measurements.
What confused me is that μS (mirco Sievert) and μGy (micro Gray) would be the same unit.
But one is absorbed radiation dose (Gray) and the other
Dose equivalent radiation (Sievert).

How did I measure?

I used the build in Gamma probe of the PDR-7001 device. No signifance distance, mantles where hold against the unit.
Since mantles are packed in multiple amounts I did measure single mantles as well as multiple (see amount of mantles). The mantles where measured in their original packages, paper or plastic. Seperate or as the package amount.
For every reading I waited, depending on a stable reading, 5-10min.

www.petromax.nl - Radiation
View of internal the Gamma probe (DT-7002), removed from the main unit. Note the yellow dot, which marks the center of the probe.

www.petromax.nl - Radiation
An old mantle placed on the units yellow measuring dot.

Table of measurements:

Stralings_metingen - www.petromax.nl
Some observations:
- looks like in generall all mantles show more or les the same result somewhere around 0,50 - 0,65 μGy/h.
- the mantles marked radioactiv (AUER) don't differ much in value.
- I skipped the CPS because of time, every measyrement is 5 - 10min.
- values are not stable, they go up and down over time. 0,1 up/down is normal.
- Used: an IM7001 FAG Kugelfischer with built in DT7002 probe

Besides the old AUER, I have no mantles that state: non radioactive or radioactive !
So I don't have a real comparishment on one or the other.
I thought the Graetz mantles which I got from the Graetz factory in Altena Gemany, must be radioactiv but they don't show very different (higher) values.

Only the "No Name" brand mantles show no radiation at all, the values are as high or not higher then the background "noise".

The old Primus mantles seems to win with 0.8 μGy/h.

So back to the first question and its implication: safety.

Well normal handling of gas mantles of any kind include these "rules" which are shared among lantern collectors and mantle users worldwide:
- handle mantles as if they are radioactive and can cause harm
- used mantles, should be disposed of carefully. Don't blow any remains away, preventing inhaling particles. A good manor is to put a plastic bag around your hand and remove the mantle in such a way that all the remains get in the bag. Close the bag.
- don't eat or drink while handling mantles and wash your hands after working with them.
- store mantles in a dry safe place. Safe would be a metal tin and out of reach of curious people and /or children, anymals etc.

I end with a quote of a fellow lantern collector:

As a rough estimate, its stated that the dangerous dose of radiation is about 100milliSieverts being accumulated in the human body over a period of one year. 100milliSv = 100,000microSv.
Assuming a year has 8760hrs, then its about 100,000microSv/8760hrs = 11.42microSv/hr.
That would be roughly equivalent to strapping a piece of radioactive mantle permanently on your body for a year. I don't think anyone wears a piece of mantle necklace 24hrs a day.
So I'd say, its still quite safe to be using these radioactive mantles, so long as we are aware and take necessary precautions in their handling, storage and disposal.