Which thermometers should NEVER be used due to risk of contaminating processing solutions?

• A. Mercury thermometers
• B. Mercury or Alcohol thermometers
• C. Digital thermometers
• D. Alcohol thermometers

Answer: (B)

Contamination of processing solutions happens when a thermometer releases a liquid that can alter the chemistry of the developer or fixer. Mercury thermometers use liquid mercury; if one breaks in the processing bath, mercury can contaminate the solution and pose serious toxicity concerns, so they are not used around processing solutions. Alcohol thermometers contain alcohol; if they fracture, the alcohol spills into the solutions, changing their composition and introducing flammability risk. Digital thermometers, with sealed electronic sensors, don’t release any liquid, so they won’t contaminate the solutions and are preferred. Therefore, mercury and alcohol thermometers should never be used in areas where processing solutions are handled.