The combination of certain household cleansers and products can have toxic and even fatal results.

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As confirmed cases of the novel coronavirus, or COVID-19, continue to rise, the United States Centers for Disease Control and Prevention recommends daily frequent disinfecting of repeatedly touched surfaces and objects like tables, countertops, light switches, doorknobs, cabinet handles, cellphones, computer keyboards and appliances.

But even in a pandemic situation, more is not better when it comes to cleaning solutions. The CDC recommends cleaning surfaces with plain soap and water. To disinfect surfaces, the recommendation is a simple solution of bleach and water at a ratio of one-third-cup of bleach to a gallon of water; alcohol solutions with at least 70 percent alcohol; or commercial household cleaners and disinfectants.

And while it’s tempting to mix your own batch of cleanser or disinfectant or increase its potency, the results can be dangerous or deadly. Here are five household chemicals and their combinations to avoid at all times:

Bleach and ammonia: This combination forms the toxic vapors chloramine and chlorine gas that burn your eyes and respiratory system. If there is enough ammonia, the combination can produce hydrazine, which is not only toxic, it’s a potential explosive.

Bleach and rubbing alcohol: Bleach reacts with the chemicals in rubbing alcohol to produce chloroform. Breathing enough chloroform can lead to unconsciousness and, in extreme cases, death. The mixture can also burn skin.

Bleach and vinegar: Mixing any weak acetic acid product — vinegar or lemon juice for example — with bleach forms chlorine gas. This gas can harm the skin, mucous membrane and respiratory system. High concentrations can be deadly.

Vinegar and peroxide: Any weak acetic acid mixed with peroxide will produce peracetic acid. The corrosive creation can irritate the eyes and nose and cause chemical burns to the skin.

For now, the safest course is to stick to the CDC recommendations and always use commercial products according to the manufacturer’s instructions and heed all safety precautions printed on the labels.

Julia Bayly is a reporter at the Bangor Daily News with a regular bi-weekly column. Julia has been a freelance travel writer/photographer since 2000.