Geiger Counter Question

[worriedsick79]

TL;DR

Possibly contaminated device

Hi,

I’ve recently purchased two geiger counters from Amazon, GQ GMC-800 and GQ GMC-300S, because someone in my life was supposed to receive RAI. Ended up my relative didn’t need the treatment. I’ve heard about granite countertops being potentially radioactive, so decided to open the devices and test things around the house. I opened both on my bed… without thinking anything of it.

One appeared used and didn’t have the protective screen film. I used the GQ GMC-800 to measure things around the house. I got anywhere from 3-31 CPM. I measured an item which showed 11 the first time and went up to 26 later, the second time I measured. I touched the meter directly to items, such as my sofa, countertop, pillow, etc. Then I started worrying that if this product was used maybe it was contaminated with radioactive materials. I also took it outside, and the readings of concrete and a brick were like 14 cpm.

If the device was actually contaminated, would the readings be so low? I am terrified as I have a small child at home. Is there anything I could do now?

 

[.Scott]

According to the GQ GMC-800 Geiger Counter User Guide:

Background Safe Levels Suggested background readings levels: 1. Safe level. Less than 50CPM or 0.25uSv/h. Nothing to worry about 2. Attention level. 51CPM – 99CPM. OR 0.26uSv/h – 0.39uSv/h. Unnaturally high, time to figure out what is wrong 3. Warning level. More than 100CPM or more than 0.40uSv/h. Dangerous to stay in this area for long.

So, all of the reading you have taken are considered by the manufacturer to be "safe background levels".

The other issue is "integration time". "CPM" stands for "counts per minute". If your CPM is less than 30, don't expect "30" to show up every second. The device is integrating over time (apparently, over a rolling 30 second period). So, if you put this on the sidewalk and only wait 5 seconds, you won't get a "sidewalk" reading - you'll get a path-to-the-sidewalk reading.

Here's another excerpt from the manual:

After GMC-800 is turned on, it will show the background radiation reading. The background radiation reading (in CPM) indicates the nature radiation detected at that minute. This reading may change from time to time and location to location. To get an accurate reading, user may need to get an average value over a longer time period.

All that said, if you think that you have soiled your sidewalk with this level of radiation and you want to clean it up, then put your garden hose on it's fast tight stream setting and rinse the area away onto permeable ground.

 

[worriedsick79]

According to the GQ GMC-800 Geiger Counter User Guide:

Background Safe Levels Suggested background readings levels: 1. Safe level. Less than 50CPM or 0.25uSv/h. Nothing to worry about 2. Attention level. 51CPM – 99CPM. OR 0.26uSv/h – 0.39uSv/h. Unnaturally high, time to figure out what is wrong 3. Warning level. More than 100CPM or more than 0.40uSv/h. Dangerous to stay in this area for long.

So, all of the reading you have taken are considered by the manufacturer to be "safe background levels".

The other issue is "integration time". "CPM" stands for "counts per minute". If your CPM is less than 30, don't expect "30" to show up every second. The device is integrating over time (apparently, over a rolling 30 second period). So, if you put this on the sidewalk and only wait 5 seconds, you won't get a "sidewalk" reading - you'll get a path-to-the-sidewalk reading.

Here's another excerpt from the manual:

After GMC-800 is turned on, it will show the background radiation reading. The background radiation reading (in CPM) indicates the nature radiation detected at that minute. This reading may change from time to time and location to location. To get an accurate reading, user may need to get an average value over a longer time period.

All that said, if you think that you have soiled your sidewalk with this level of radiation and you want to clean it up, then put your garden hose on it's fast tight stream setting and rinse the area away onto permeable ground.

Thanks. I’m obviously not worried about the sidewalk, just included that detail since that’s another thing I tested. I’m worried about my house. So if the readings were background level, does that mean the counter itself didn’t arrive contaminated? I’m very new to this.

 

[.Scott]

Thanks. I’m obviously not worried about the sidewalk, just included that detail since that’s another thing I tested. I’m worried about my house. So if the readings were background level, does that mean the counter itself didn’t arrive contaminated? I’m very new to this.

It means that if it was contaminated, the contamination is not being picked up by the counter - so (assuming the counter works) it's not very radioactive.

 

[worriedsick79]

It means that if it was contaminated, the contamination is not being picked up by the counter - so (assuming the counter works) it's not very radioactive.

Ok, thanks!