Vinegar and bleach should never be mixed as their chemical interaction produces chlorine gas, which is highly dangerous. This reaction occurs due to the acidity of vinegar (containing acetic acid) and the alkalinity of bleach (sodium hypochlorite). When combined, they create a potentially lethal chemical compound. Inhaling chlorine gas can lead to severe respiratory problems and even be fatal in high concentrations. To ensure safety, always use cleaning products as directed, and never mix bleach with any other substances, particularly vinegar, to prevent the formation of hazardous gases.