Thanks, kinda what I suspected.
The lateral-flow tests are not sensitive enough to detect COVID in exhaled fog or droplets. But if you breathe enough of those droplets in, you will likely get infected.
My wife contracted Omicron a week or two ago, and I soon developed it as well, even though we are both fully vaccinated and boosted.
I administered the BinaxNow lateral-flow test to my wife, who had a scratchy cough and needed lots more sleep than normal, and she was strongly positive. (I didn't test myself on the assumption that I already know the answer - I had developed the same cough and sleep demand.)
In this test, one scrubs the inside of both nostrils up to 3/4" (19mm) in with a swab, collecting whatever is right on the mucosal skin that lines the nostril, and becomes a home for COVID. This is far more direct than sampling the droplets emitted while speaking. The scrubbing doesn't really hurt, but is maddeningly ticklish.
She probably got it from her immediate family, many of whom came down with Omicron as well. (There was a lot of travel because there was a death in the family.) In the immediate family, all are vaccinated and none of these infections were serious, none requiring medical attention.
I used the NHS rapid antigen tests kits, I had about 20 so tried various ways including coughed up sputum. Everything showed strongly positive with the exception of the breath condensate effort.
I think it was my daughter that brought it home from work but not sure, my symptoms were loss of smell, constant headache (the worst part for me as it robbed sleep), average cold symptoms. The tests I collected below, the bottom rack taken using the suggested method. From noticing symptoms to testing clear was 7 days.
GF tested positive a couple days after I did and had a similar trip.
The articles I read about testing for Covid in breath using the Gesundheit Machine were varied, which also led me to question. Seems to be a paper out there to suit any view.