Which chemical is described as an irritant and corrosive used in the laboratory hood?

• A. Ammonium hydroxide
• B. Formalin
• C. Ethanol
• D. Acetic acid

Answer: (A)

Ammonium hydroxide is a strong base whose vapors and solutions are both irritating and caustic. When concentrated, it can cause chemical burns to skin and eyes and irritate the respiratory tract if inhaled. In the laboratory, it’s commonly handled under a fume hood to control and vent the irritating ammonia vapors, matching the description of an irritant that is also corrosive.

Formalin is a hazardous irritant/toxic fixative, but its primary association is preservation, not described as corrosive to the same degree. Ethanol is flammable and irritating at high concentrations but is not considered corrosive in typical lab exposure. Acetic acid is corrosive, but the combination of being a widespread irritant and specifically serving as a caustic agent in hood use aligns best with ammonium hydroxide.