But it clearly is to identify smokers, not people with dodgy heaters - Eilidhbelle was referred, despite not smoking!
Yes, I admit that that is one in a million, and so screws with the stats a lot less than not doing the test.
As for obesity, since I am, I can tell you that they took my word for my weight and height (something that I'm endlessly regretting being truthful over, as they are freaking out in complete disregard for the actual increases in risk), and haven't bothered to even ask to weigh me at all - which seems a bit silly given all the fuss, drugs, and appointments they're trying to foist on me, and how close I am to the magic BMI line they're so upset I've crossed..
If they can take my word for that, and cause a lot more expense than sending me to an 'eating cessation' unit, then I think they should be able to take my word on if I smoke or not.