Cleaning & SanitizingQuestion 135 of 319
Why might a quaternary ammonium (quat) sanitizer fail to disinfect a surface even when mixed at the correct concentration?
a.The label color faded in storage
b.The sink is made of stainless steel
c.The water is very hard (above the limit on the product label, typically 500 ppm hardness)
d.The water was at room temperature
Explanation
Quat sanitizers can be deactivated by hard water. If mineral content exceeds the limit on the product label (often 500 ppm, sometimes lower), the quat binds to minerals instead of microbes and loses effectiveness. Operators must follow the label and may need a water softener or a different sanitizer.
Law Reference: Cal. H&S Code §114099.1This topic, taught in full in the Food Handler Card guide. Food Handler Card — Complete Study Guide (2026) — PDF + EPUB, $9.99 · 14-day refund →
Practice all 319 questions free — no signup required.
Own the complete Food Handler Card guide — PDF + EPUB, $9.99 →
Related questions on this topic
- Food-contact surfaces (counters, cutting boards, utensils) must be made of materials that are:
- A cook accidentally mixes a chlorine sanitizer at 400 ppm, much higher than the required range. What is the problem?
- Chlorine sanitizer is MOST effective when the solution's pH is:
- One limitation of using iodine as a sanitizer in a food facility is that it:
- Sanitizer test strips should themselves be checked because:
- A small front-counter station uses single-service paper towels to wipe minor spills. After wiping a counter, what should the worker do with the towel?
Last reviewed: · editorial process
PrepPass team · Verified against California Food Handler Card Exam · How we review