Want to feel like an IDIOT ?? Come here , ask a question, get a reply to shake the bottle better, get instant results on your next test !! Nitrates went from testing zero, to pushing 80 !! Now to get them to head in the other direction !!! The test kit is brand new, and I trusted GLA to make sure my KN03 was actually KN03, so I was lest with the ' shake it up' option, and it worked !!