Are Natural Gas Detectors Necessary?

[NeverDie]

I'm not sure what others do, but I try to compare common risks like this to the odds of dying in a car crash (~2% odds, IIRC) as a rough way of calibrating whether a risk warrants mitigation or not. The nice thing about radiation is that it's easy to measure and the odds are easy to quantify.  I'm not sure what the odds are on NG, but I'd be curious to know.

 

[ano]

I'm not sure what others do, but I try to compare common risks like this to the odds of dying in a car crash (~2% odds, IIRC) as a rough way of calibrating whether a risk warrants mitigation or not. The nice thing about radiation is that it's easy to measure and the odds are easy to quantify.  I'm not sure what the odds are on NG, but I'd be curious to know.

You may want to check out this chart. http://www.vdh.virginia.gov/epidemiology/radiologicalhealth/radon/health.htm
 
If your radon level is 4pCi/L, which is the limit specified in the U.S., you will have a 5 times chance of getting cancer from radon than dying in a car crash.  Of course, that 5X rate only applies if your home is AT the allowed level. Your home could be much higher than that, since few states require any testing.

 

[NeverDie]

You may want to check out this chart. http://www.vdh.virginia.gov/epidemiology/radiologicalhealth/radon/health.htm
 
If your radon level is 4pCi/L, which is the limit specified in the U.S., you will have a 5 times chance of getting cancer from radon than dying in a car crash.  Of course, that 5X rate only applies if your home is AT the allowed level. Your home could be much higher than that, since few states require any testing.

Luckily I'm not a smoker, but even so, those are meaningful risks, and I can see why you're taking the steps you are.  I think I'd do the same if I were in your shoes.  On the other hand, I wonder whether the presence of mitigation equipment might unfairly stigmatize a house when it's time to sell, even though it would actually be safer than unmitigated houses in the same general area.
 
The link you referenced says it's hard to get below 2pCi/L indoors.  In your experiments, does increasing air exchanges by, say, turning on bathroom exhaust fans make a significant dent in your measured indoor radon levels?  I wonder how many air exchanges per hour you would need to approach the radon levels found outdoors?  I really haven't thought about it, but I wonder whether even carbon filtration would make a difference.  Since you've got the measurement gear, perhaps you've looked into or tried it already.

 

[ano]

I recently sold my previous house with the equipment installed. I think one person looking at the house asked about it, but the house sold in one day over asking price, and neither of the two people making offers even asked. Its really not a big deal. In fact I think its positive. O.K. this house has it under control, well what about all those other houses we looked at? Could there be a problem here? 
 

The link you referenced says it's hard to get below 2pCi/L indoors.  In your experiments, does increasing air exchanges by, say, turning on bathroom exhaust fans make a significant dent in your measured indoor radon levels?  I wonder how many air exchanges per hour you would need to approach the radon levels found outdoors?  I really haven't thought about it, but I wonder whether even carbon filtration would make a difference.  Since you've got the measurement gear, perhaps you've looked into or tried it already.

Bathroom fans CAUSE the problem actually.  So imagine your home as a box, and in this box your sucking out air and creating a vacuum. But the main leaks in a home are cracks in the foundation and the millions of pipes that come up from the ground. The vacuum sucks the radon into your house. If you leave doors and windows open, the levels will drop, but you can only do that when the weather is nice.
 
A very easy solution is to just dig down to below the foundation where they place several inches of gravel, and vent that out through a 4" pipe.  Even without a fan its pretty effective, because its an easier path for the radon to vent out the pipe then to go through your floors. This also prevents whatever other earth gases are out there and vents them. People seal all the doors and windows of their house, but don't realize builders care very little about sealing holes for pipes and wires from the ground. Plus I've never owned a house that didn't have some foundation cracks.

 

[NeverDie]

I recently sold my previous house with the equipment installed. I think one person looking at the house asked about it, but the house sold in one day over asking price, and neither of the two people making offers even asked. Its really not a big deal. In fact I think its positive. O.K. this house has it under control, well what about all those other houses we looked at? Could there be a problem here? 
 
Bathroom fans CAUSE the problem actually.  So imagine your home as a box, and in this box your sucking out air and creating a vacuum. But the main leaks in a home are cracks in the foundation and the millions of pipes that come up from the ground. The vacuum sucks the radon into your house. If you leave doors and windows open, the levels will drop, but you can only do that when the weather is nice.
 
A very easy solution is to just dig down to below the foundation where they place several inches of gravel, and vent that out through a 4" pipe.  Even without a fan its pretty effective, because its an easier path for the radon to vent out the pipe then to go through your floors. This also prevents whatever other earth gases are out there and vents them. People seal all the doors and windows of their house, but don't realize builders care very little about sealing holes for pipes and wires from the ground. Plus I've never owned a house that didn't have some foundation cracks.

That's interesting.  When I ran our radon test, I did it when the house was vacant, with no exhaust fans and no HVAC running, because at the time I thought that would be a worst case scenario.  I wonder how much different the results would be now that we're living in it.  I wouldn't be suprised if most HVAC's create some amount of negative pressure, but I don't have any actual data on that.
 
I do have one exhaust vent that's an ERV, but the other six are just regular fans that don't supply their own recovery air.
 
I'm not sure what goes into a good radon sensor, but I suppose having a way to datalog it, using an arduino or the like, so it could be plotted would be pretty useful if, as you say, the measured value swings over a meaningfully wide range.  Did you ever try looking automating your collecting of datapoints beyond high, low, and average?

 

[ano]

I'm not really sure that plotting it is valuable. My detector keeps an average.

 

[lleo]

Beside the negative pressure bathroom fans and clothes dryers create, there is the simple stack effect of warm air inside the house, especially if you have leaks to your attic. As warm air raises it pules in cooler air through the cracks in the basement. This is more relevant obviously in winter and cold climate regions.
Radon is a gas, as ano mentioned, but the risk is when you inhale it and the very moment while in your lung the gas molecule emits an alpha particle and decays into a heavy metal radioactive byproduct, radioactive lead actually which has a half-life of 20+ years. This means that whatever gets stuck in your lungs, the radioactivity will decrease to half in about 20+ years. Radon gas itself has a half-life of ~3.5 days, meaning that if infiltration is stopped and ventilation is dismissed, the radioactivity is reduced to half in 3.5 days.
Just before you start thinking is all over... remember that living organisms have encountered this in their evolution and have some defenses against it, such as DNA correction and repair. So if you factor in a variability from being in the basement in the right (or for that matter bad) time combined with inhaling the specific molecule that is decaying next to a replicating cell in your lung and combined with risk factors one has (i.e. smoking or others) results that the effect seems almost random and are best described as relative incremental risk.

 

[NeverDie]

I don't know if it's true or not, but I've read that the mail-in radon tests are still considered the gold standard.  Any recommendations or thoughts on which of the mail-in radon tests is the most accurate?  I think the one I did (about 5 years ago, so I'm now hazy on the details) was probably an activated carbon one.  I just noticed there's one now for gathering long-term test data anywhere from two weeks up  to a year.  With that one when you mail it in, they count the alpha particle tracks on some kind of foil/film.  The advantage of a longer test interval is that will incorporate the seasonal and environmental swings that may not be accounted for in a short-term test.
 
Not surprisingly, one guy already hooked up an arduino to read his Safety Siren 3 and plot the values in real-time to the internet for anyone who wants to see them:  http://www.howmuchsnow.com/arduino/radon/

 

[ano]

I think the mail-in detectors are fine, but a short-term reading doesn't really help you much. Many people buy these things take a 2 day reading, and assume they are good or not, but its just a starting point. You either need a 6 month or year test, or some device where you can see the daily changes so you get an idea of the readings. The devices are not super accurate, but it really doesn't matter. I'd say they are accurate within 25-35%. Look at the thermostat you have outside your house. It the temp reads 80 but its really 83, is that going to change your clothes choice. If it reads 40 but its really 43, I don't think your clothing choice would change much?  And do you need to plot the outdoor temp every hour or minute to know if you need a coat out?

 

[NeverDie]

I think the mail-in detectors are fine, but a short-term reading doesn't really help you much. Many people buy these things take a 2 day reading, and assume they are good or not, but its just a starting point. You either need a 6 month or year test, or some device where you can see the daily changes so you get an idea of the readings. The devices are not super accurate, but it really doesn't matter. I'd say they are accurate within 25-35%. Look at the thermostat you have outside your house. It the temp reads 80 but its really 83, is that going to change your clothes choice. If it reads 40 but its really 43, I don't think your clothing choice would change much?  And do you need to plot the outdoor temp every hour or minute to know if you need a coat out?

I found instructions for how to make a raspberry pi radon detector.  It uses a geiger tube, and it claims to be accurate to within about 20% for radon.  You calibrate it yourself using some inexpensive uranium ore that has been measured and certified for calibration purposes.  So, I'm guessing the safety siren 3 is a similar design for measuring radon, as I've read it is also accurate to within about plus or minus 20%.  The geiger tubes operate at around 500-600V, which is possibly also why the safety siren plugs in to line voltage.  Anyhow, just idle speculation, as I haven't dug into it any more deeply than that.

 

[ano]

Many years ago I built a Heathkit geiger counter that still works today. (Remember those guys?) I hooked a counter to it so I could keep counts over time. so how do you convert counts per minute to a radon level?

 

[NeverDie]

Many years ago I built a Heathkit geiger counter that still works today. (Remember those guys?) I hooked a counter to it so I could keep counts over time. so how do you convert counts per minute to a radon level?

A rough-and-ready answer to that is given in Chapter 14 of http://84.209.254.175/linux-pdf/RaspberryPi/Raspberry_Pi_Projects_for_the_Evil_Genius_2014.pdf
  

 

[lleo]

The radiation emitted by the radon gas decay is low power alpha, typically not even able to penetrate skin. While you can detect this, the issue is the difficulty to discern it from natural background radiation. There are several technical/engineering solutions for this, but these also increase the price of the detectors. Most require frequent recalibration to be effective and reasonably accurate. Again, the risk is not necessarily the alpha radiation, but the byproducts of the decay chain which are not gaseous under atmospheric conditions and more powerfully emit with a very long half life.
 
For those interested here is a technical review: https://www.aarst.org/proceedings/2005/2005_05_Intercomparison_of_Sensitivity_and_Accuracy_of_Radon_Measuring_Instruments_and_Methods.pdf
 
Low-cost Geiger counter as radon detector is available here, with a lot of technical info to also consider. http://www.aw-el.com/
 
Up until recently I used to travel with my trusted hand-held Geiger counter, and had fun sending it through the screening process at airports, as well as "forget it" in my pocket in the "nude" scanners, but would not advise anyone doing it anymore unless you are ready for a lot of questions and unfriendly looks.

 

[Del91574]

That's interesting.  When I ran our radon test, I did it when the house was vacant, with no exhaust fans and no HVAC running, because at the time I thought that would be a worst case scenario.  I wonder how much different the results would be now that we're living in it.  I wouldn't be suprised if most HVAC's create some amount of negative pressure, but I don't have any actual data on that.

A building with forced air is always going to be positive compared to the outside, which is part of the reason of requiring return air plenums....if you can't return the air to the furnace, you're going to create too high a static and essentially starve the furnace/blower. In the case of a residence, the pressure is going to go out the path of least resistance, but then that will end up dragging in fresh air to replace it via the paths of least resistance.
 
It's very difficult to maintain a space at a negative pressure compared to a higher area. We're commonly doing it in high risk areas or hospital rooms and it's far easier to overpressure than make a space negative.

 

[NeverDie]

Residential filters that utilize activated carbon do exist.  Probably even your local Walmart has some in stock.  As a proof of concept, I suggest plopping one of those simple units down, initially in a closet with your radon detector, and see if it slashes your measured radon level.  If so, then through experimentation, you could figure out how many air exchanges it would take, and from that figure a cost to do your whole house.  Maybe it wouldn't take many air exchanges, and the cost would be low.  Anyone happen to know?
 
By the way, I'm not against the under-the-slab mitigation for those who want to go that route.  I don't see that it's necessarily either-or.  Rather, I'm wondering whether simpler and less expensive might be good enough for those of us whose radon levels aren't especially high by the reckoning common in the US.  I'm wondering because, according to Wikipedia, some other countries appear to have already legislated for lower levels.  Since other countries have decided that a better target is 2pCi/L rather 4pCi/L, is there an easier and cheaper way to reach that level?  In a lot of areas of the US, 2pCi/L is lower than even the regional average: