Disinfection requires the right concentration AND contact time. Alcohol 70–85 %, chlorine 0.1 % (1000 ppm) at pH > 8–9, quaternary ammonium compounds 0.5–5 %. But disinfection is not a routine: it is only used where indicated, the agent must match the microorganism, and its effect must be documented according to EN standards.
Introduction
Disinfection is not the same as cleaning: you must clean FIRST, and then hit both the right concentration and the required contact time before the agent actually kills micro-organisms. Here are the guideline working concentrations.
Place of disinfection: only where indicated
According to the national infection hygiene guidelines (NIR), thorough cleaning is the main rule — disinfection is only used where there is a specific reason for it, not as daily routine on all surfaces. Routine over-disinfection is neither necessary nor free: it stresses materials, the environment and the user and can in the long term contribute to resistance. Disinfection is, however, indicated for example at spills of biological material, on patient-near surfaces under special circumstances and at known infection.
| Medium | Use concentration | Note |
|---|---|---|
| Alcohol (ethanol) | 70–85 vol/vol % (≈ 63–80 wt/wt %) | For surface disinfection. |
| Chlorine (hypochlorite) | Free/active chlorine 0.1 % (1000 ppm); against spores 0.5 % (5000 ppm) | Hypochlorite (pH > 8–9): 1000 ppm for 1–5 min; against spores 5000 ppm for 10–15 min. Acidic hypochlorous acid (pH < 6–7) works at 300–400 ppm. |
| Quaternary ammonium compounds | 0,5–5 % | Good cleaning effect, but limited/uncertain effect against gram-negative bacteria. |
The agent must match the microorganism
No disinfectants work equally well against everything. The most important example is spore-forming bacteria: Clostridioides difficile forms spores that are very resistant and are NOT inactivated by alcohol — a chlorine product is required here. Alcohol also has only variable effect against unencapsulated (naked) viruses like norovirus. Therefore choose the agent based on what you need to target.
| Medium | Works against | Weak/no effect against | Practice |
|---|---|---|---|
| Alcohol (ethanol) 70–85% | Many bacteria and enveloped viruses | Strains (e.g. C. difficile); variable against norovirus | For quick surface disinfection; the surface must be kept wet. |
| Chlorine/hypochlorite (free chlorine 0.1–0.5 % ≈ 1000–5000 ppm) | Broad spectrum: bacteria, viruses (including norovirus) and — given sufficient time — spores | — | Against spores (C. difficile) and norovirus: 5000 ppm for 10–15 min at pH > 8–9; rinse afterwards and ventilate. |
| Quaternary ammonium compounds (0.5–5 %) | Many gram-positive bacteria and enveloped viruses | Limited/uncertain against gram-negative bacteria, spores and naked viruses | Good cleaning effect; not for traces. |
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