[aprssig] APRS to the planet rescue?

KF4LVZ aprssigZbr6 at acarver.net
Mon Apr 3 12:00:57 EDT 2017

On 2017-04-03 07:56, Robert Bruninga wrote:
> Here's a project.  Add a $4 Methane detector to your APRS mobile and help us 
> find the bad methane leaks.  Google is adding it to their maping cars.  Maybe 
> Amateur Radio and APRS could help?
> https://mail.google.com/mail/u/0/#inbox/15b2521854ccaa63
> Apparently the 2:1 advantage of replacing the high carbon emissions of coal with 
> natural gas, overlooks the fact that the methane released with natural gas 
> extraction methods is 84 times worse than carbon as a green house gas and may 
> more than offset any advantages.
> Just one methane leak a few years ago did more damage than about a million cars 
> a day before it was plugged months later
> .http://www.businessinsider.com/methane-gas-leak-porter-ranch-los-angeles-disaster-largest-in-history-2016-1
> Anyway, a $4 sensor and a tiny processor could add a flag to our mobile packets 
> somehow  when levels exceeded some background level
> Though I am not sure if the sensitivity of these $4 sensors is good enough to 
> find the outdoor area low level leaks, or only detects high concentrations...
> I wish I had the time to make one and experiment with the concept.  It would 
> make a great fun project. I used to thing a cheap radiation detector would let 
> APRS contribute to plotting radiation hot spots, but I fear the natural gas 
> leaks and fracking damage is going to kill us first.
> My thoughts on adding this to APRS is to simply have a processor send out a 
> modified STATUS text when a detection is made.  Since APRS was designed around 
> the status being merged-on-receipt with the most recent posit, this is a way of 
> nailing down the location of high methane levels or leaks.
> Status could simply be >CH4=XXX where XXX is the reading.  Format of XXX will be 
> determined to  give reasonable scale over expected detections.  Then the APRS 
> map could selectively plot any detections.
> Anyone have more experience with these sensors and the levels of detections 
> expected?
> Bob, wb4apr

No, the sensor you want to use is a passive unit designed for indoor air
quality monitoring (specifically looking for a hazardous leak that could
result in an explosion).  The unit in the StreetView car is a gas
sampling analyzer (sniffer) and probably costs closer to $1000  as it's
looking for concentrations on the level of single and double digit

More specifically, according to the paper the unit in the StreetView car
is from Picarro.  It's an infrared spectrometer based detector.
Because it's a spectrometer it can measure into the low
parts-per-billion levels which is critical for detecting a leak outdoors
where the atmosphere will dilute the gas quickly.  The cheap sensor you
describe is a chemical cell sensor whcih is only good at concentrations
above 200 parts-per-million, so already five orders of magnitude poorer
sensitivity than the StreetView car.  Again, the $4 sensor would work
for detecting a sudden leak in your kitchen in order to sound an alarm
or turn off a valve in some automated fashion (mainly if the home is

However, even this cheap sensor is worse than your Mark 1 olfactory
sensor (human nose) because the main additive to natural gas for
detecting a leak is t-butyl mercaptan and the nose can pick up the smell
to a level of 0.33 parts-per-billion, equal to the much more expensive
Picarro sensor.

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