[gumby]

Actually CH4 is pretty well distributed, especially in the northern hemisphere . The pictures / videos you linked to were emissions pictures. We have some good concentration maps we generated from from the ESA Copernicus Tropomi data. I don't know how to link to those internal pictures, but you can probably find similar images right on an ESA site or one of the university sites that use the data.

As for concentration: that's an excellent question. I'm not sure how much I should say right now (though as soon as some of the scientists appear on our website it'll be obvious from their publication record, if the comms "team" -- really just part of one person -- hasn't already written more by then). I can tell you that the lab work we are scaling up just used outside air -- a pipe stuck out the window -- as its air source, not some special high concentration mixture made in the lab.

I believe you can buy home water filters that extract higher molecular weight contaminants like arsenic in low ppb levels, but I'm not sure how applicable that really is :-)