If you'd tried a term search on 'ventouse' with 'also search reverse language pair', you ought to have found at least one previous EN > FR entry that might have helped you.

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Note added at 11 minutes (2015-12-03 20:37:23 GMT)
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One of a small number of Ghits:

the complete range of oil and gas fired condensing boilers

http://www.haldane-fisher.com/fs/doc/plumbing-and-heating-bo...

coaxial balanced flue system - Ø 80/125. Description. Code. Equiv Length. Horizontal Terminal. FBF. 1.0m. Vertical Terminal. VBF. 2.0m. 1m Extension. F3. 1.0m.

In fact, 'concentric balanced flue' gets rather more Ghits — but in truth, balanced flues are so commonly concentric / coaxial, it is simply rarely mentioned, as you will see if you research images of 'balanced flues'

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Note added at 12 heures (2015-12-04 09:00:02 GMT)
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In answer to Chris's comment, I was only just the other day studying the installation manual for my own condensing boiler, and was horrified to see there a number of other flue configurations that I had not seen before — and as Chris says, some of them looking horribly fiddly to implement!