Why should mouth pipetting be avoided in the lab?

• A. Ingestion of toxic liquids is possible.
• B. It provides the most accurate measurements.
• C. It helps prevent contamination.
• D. It is faster than using a mechanical pipette.

Answer: (A)

Mouth pipetting is unsafe because many lab liquids are toxic or corrosive, and using the mouth creates a real risk of ingesting or drawing vapors through the lips and airway. That direct path bypasses any protective controls, so even small splashes or incorrect suction can expose you to hazardous chemicals. Mechanical pipettes with disposable tips provide a sealed, controllable means of transfer, greatly reducing exposure and contamination while improving accuracy. The idea that mouth pipetting is the fastest or most accurate is false, and it can actually introduce contamination from saliva.