BACTOSCOPE (16) H2S STRIP, which is a type of field test kit used to check the microbiological quality of drinking water. It detects the presence of hydrogen sulfide (\(H_{2}S\)) producing bacteria, which can indicate contamination. The test involves adding a water sample to a pre-sterilized bottle with a media-filled strip, waiting 18-48 hours, and observing a color change. An unchanged yellow color suggests safe water, while a black color indicates it is unfit for drinking and needs to be boiled or chlorinated.