Not trusting my plumber I decided to take the stink investigation into my own hands and dot these around the house.

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Some time ago I had nasty smells in my kitchen and no I didn’t leave an egg salad on the table for a few weeks or a bucket of prawns in the sun... The smell was hydrogen sulfide or commonly know as sewer gas. My first step was to get a plumber in to try and trace the issue, it was intermittent and not constant so it was quite difficult to pinpoint. To me it was an issue with the venting of the outside main sewer link into my house but the plumber assured me that the venting was done fine as he worked on the house originally when it was renovated. About once a day, usually in the mornings we got this horrific stink only for a few minutes or so. Not trusting the plumber after all this I decided to look into Gas Sensors and found the Figaro TGS 2602 sensor which does loads of other gasses apart from hydrogen sulfide see data sheet http://www.figarosensor.com/products/2602pdf.pdf. I bought a bunch of these and hooked them up to Arduino UNOs and placed them all over the house. Well believe it or not the first sensor to go off was not in my kitchen but in my attic and as hydrogen sulfide is a heavy gas I was in a quandary. So I had a look inside the roof to attic cavity and lo and behold the vent pipe did not go out onto the roof. This meant that the gas while heavy was going down the wall cavity three flights and under the kitchen floor to the other side of the room. Problem solved, plumber on end of angry phone call....