Decontaminate the work surface
Disinfect before and after, and leave it wet for the time on the label. Learn why a quick wipe that dries in seconds does almost nothing.
- Killing organisms takes time, not just contact: A disinfectant works while it is wet on the surface. Removing it early stops the process partway, which is why the label states a time.
- A bench is a reservoir: Whatever was on the bench can reach an open plate, and whatever you spill stays for the next class unless the surface is treated.
Prerequisites are inferred: pending teacher review.
Re-learn the skill with worked practice and clear examples.
Now handle the parts of the surface people forget, and the towel afterwards.
A group treats the flat working area of the bench thoroughly at the end of a culture lab. Which commonly missed surfaces should also have been included?
Reviewed- A.The undersides of the four bench legs
- B.The drawer handle, the tap and the bench edge
- C.The ceiling tiles directly above the bench
- D.The window sill and the classroom noticeboard
Show the worked solution ▾
Answer: B. The drawer handle, the tap and the bench edge
- Step 1: Follow the hands, not the work: The question is not where the culture sat, it is where a gloved hand went during the session.
- Step 2: List those points: Handles, taps and the front edge of the bench are touched constantly and cleaned rarely.
Why it's right: Contamination travels on hands, so the surfaces at risk are the ones hands touched, not only the ones the culture sat on. Handles, taps and the bench edge are touched constantly and treated rarely.
- A: Bench legs are below the working area and out of the hand path. They are a housekeeping matter, not a decontamination one.
- C: Nothing from a bench reaches a ceiling in normal work, and nobody touches it.
- D: A sill and a noticeboard are across the room and were not touched during the work. Treating them adds effort where nothing went.
Aligned to Handling, Preparation, Storage and Disposal · reading level ~grade 9
The paper towel used to disinfect a bench after a culture lab is still damp. What should happen to it?
Reviewed- A.It is rinsed at the sink and put in the ordinary bin
- B.It is folded and kept at the station for the next group
- C.It goes out by the route the teacher gives for that lab
- D.It is spread out to dry and used again for the next bench
Show the worked solution ▾
Answer: C. It goes out by the route the teacher gives for that lab
- Step 1: Ask what the towel now holds: It has just been dragged across a surface that carried live culture.
- Step 2: Treat it like the surface it wiped: It goes out by the route that lab's waste goes, not back into circulation.
Why it's right: The towel has just been dragged across a surface that carried live culture, so it carries the same material. Reusing it or setting it down moves that material somewhere new.
- A: Rinsing puts the material into the sink and leaves the towel wet, achieving neither containment nor decontamination.
- B: Keeping it at the station leaves a contaminated object for a group who did not create it and cannot see what is on it.
- D: Drying does not decontaminate, and reusing the towel is a direct route from one bench to the next.
Aligned to Handling, Preparation, Storage and Disposal · reading level ~grade 9
- A student clears and treats the whole hand path around a station at the end of Activity 3.1.6, not just the square where the slides sat.
Fill these in as you work through the lesson.
- Disinfectant (kills organisms on a surface):
- Contact time (how long it must stay wet):
- Reservoir (a surface that holds organisms):
- Clean to dirty (the direction you wipe):
Disinfect you set anything out and you clear up, and leave the surface for the time the product label states.
- Give the reason the bench is treated before the work as well as after it.
- Explain what a wipe that dries in five seconds has actually achieved.
- Say which direction you wipe across a bench and why.
You spray the bench and immediately buff it dry with a paper towel because it looks streaky. The surface is now dry, tidy and largely untreated: the product needed to stay wet for the time on its label, and you removed it after a few seconds. Spray it again and leave it alone.