California Cosmetology Written ExamSafety and Infection ControlMedium
A nail technician is preparing an EPA-registered quaternary ammonium disinfectant solution but adds extra water beyond the ratio printed on the manufacturer's label to make the bottle 'last longer.' What is the effect of this practice?
- AIt will still disinfect effectively because quaternary ammonium compounds are strong regardless of dilution
- BDiluting beyond the manufacturer's instructions reduces disinfecting power, making the solution ineffective and out of compliance with Title 16
- CThe extra water only affects the odor of the solution, not its efficacy
- DManufacturer dilution instructions are optional guidelines that salons may adjust as needed
Show answer & explanationAnswer & explanation
Correct answer: B. Diluting beyond the manufacturer's instructions reduces disinfecting power, making the solution ineffective and out of compliance with Title 16
California Title 16 requires disinfectants to be used exactly per the manufacturer's label instructions, including dilution ratio and contact time. Over-diluting reduces the concentration of active ingredients, weakening its ability to kill pathogens and creating a compliance violation.
Why the other options are wrong
- A. Wrong—dilution ratio directly affects the active ingredient concentration and efficacy.
- C. Wrong—dilution affects chemical potency, not just smell.
- D. Wrong—label instructions are legally binding, not optional.
Disinfectant Dilution Ratio
EPA-registered disinfectants must be mixed exactly per the manufacturer's label to maintain their proven disinfecting efficacy.
- Label directions are legally required, not optional
- Over-diluting weakens the solution
- Under-diluting can also be unsafe/wasteful
- Title 16 requires proper implement disinfection procedures
Memory trick: Follow the recipe exactly—too much water ruins the disinfecting soup