Levels of Disinfection - Is Your Disinfectant High Level, Intermediate Level, or Low Level?

Cleanliness starts with ourselves, and in our homes. In these confusing times, information abound from multiple sources telling us how to stay safe and virus free. Once we’ve followed the oft-repeated dictum to wash our hands, not to touch our mouth, eyes and nose, our next step might be to ask, what do I do next in order to keep my environment clean and virus-free?

With most of us spending more of our days at home, now may be the best time to take a nosedive in to finding out what we can do to help ensure that we mitigate and contain possible sources of contaminants in our surroundings.

There is still much to be learned, and in the interim, allow us to share some insight you may find useful. We may be surprised to find out that not all disinfectants are created equal: some have a higher kill level than others, and it would be helpful to know what you may need, depending on the surface, and what pathogen needs to be eliminated.

Level of Disinfection

Example disinfectant trade names

High-level disinfection (HLD)

·      Destruction of all microbial pathogens, including mycobacteria; levels of spores are reduced but high levels of spores are not completely eliminated at practical exposure times.

·      Cidex, MetriCide, Omnicide, Sonacide, Wavicide

·      Cidex OPA, MetriCide OPA Plus


·      5.25-6.15% household bleach (1:10 diluted to achieve 5000ppm)

Intermediate-level disinfection (ILD)

·      Destruction of all microbial pathogens; has mycobactericidal properties, but spores are not eliminated by this level of disinfection

·      BioMERS, BioSURF, BioTEXT, BM-6400TM, Gamut Plus, Instrubex-E, SEPTeFX 7D-TEXT, tb Minuteman, T36 Disinfex

·      5.25-6.16% household bleach (1:50 diluted to achieve 1000ppm)

Low-level disinfection (LLD)

·      Destruction of most microbial pathogens, but does not reliably kill mycobacteria, fungi, and non-lipid viruses; spores are not eliminated by this level of disinfection.

·      Barbicide, Zepamine-A

·      EnvironTM LpHTM, Lysol

·      Virox 5, Carpe Diem

·      5.25-6.15% household bleach (1:500 diluted to achieve 1000ppm)


Critical Items

Critical items are regarded as creating a high risk for the possibility of infection, should they be found with critical amounts of microorganisms. It is important to ensure their sterility as their accidental contact with an open cut or wound on our body carries a high possibility of disease transmittal.

Semi Critical Items

These are instruments that come in to contact with our mucous membranes or nonintact skin. Intact mucous membranes, such as the lungs and the gastrointestinal tract, are considered to be quite impenetrable to, and safe against, infections brought about by common spores, but are vulnerable to other organisms such as bacteria, and viruses.

When we refer to high level disinfection, this is institutionally defined as being able to completely eliminate all microorganisms in or on an instrument, except for small numbers of bacterial spores. Cleaning, which would include water combined with a mild detergent, followed by high-level disinfection, would be deemed acceptable to eliminate the spread and multiplication of pathogens, thus curbing transmission of infection.

Non Critical Items

These are items that come in contact with skin, but not mucous membranes. Intact, healthy skin serves as a sufficient barrier to most harmful microorganisms, thus the sterility of items coming in contact with intact skin is considered “not critical”. Most non critical items may be cleaned and disinfected on-the-spot, without needing to be gathered and transported to a separate central area for secure mass decontamination. Non critical items would include computers, bedside tables, floors, and furniture.

Noncritical environment surfaces that are frequently touched by hand, like hand rails, staircase banisters, have the potential to contribute to secondary transmission if they're touched by unclean hands. This is why the reminder to always wash ones hands is critical in mitigating the spread of germs. Handwashing is the surest and most efficient way to prevent the spread of disease, in early care education centers, schools, and workplaces. You may have a clean environment, but if you contaminate your hands, whether from sneezing, coughing or touching a dirty surface, you will, with certainty, be spreading the very diseases you wish to contain.

Mops and reusable cleaning cloths are common tools used to achieve low-level disinfection on surfaces such as table, counters, floors, and other porous or non-porous surfaces. However, it is equally imperative that they are adequately cleaned and disinfected. A good rule of thumb is to replace the disinfectant mixture they are applied with, regularly (e.g. after every three to four rooms, in no longer than 60-minute intervals). The mopping procedure can actually spread microbial contamination throughout the home, but if performed properly, is a necessary tool to keep our spaces free from contaminants that make their way inside our home. One way to support this is to frequently launder mops (e.g. daily), if mopping of floors is done daily. In one study, it was found that standard laundering provided acceptable decontamination of heavily contaminated mopheads, but chemical disinfection with a phenolic was less effective.

It is important to emphasize that disinfection should be performed, only when necessary, and steps should be taken to keep the need to disinfect low. An example of this would be in cases where outside footwear is taken inside the home. As much as possible, shoes worn outside should be kept, and left, in one area as close to the entrance of the home, to be replaced by indoor footwear, when possible.

 Apart from lowering the introduction and consequent spread of environmental contaminants that we may have inadvertently brought in from the outside, it will lower the necessity of disinfecting a bigger portion of the home. Bear in mind that not all bacteria are bad, and our biome needs to be exposed to a safe level of harmless bacteria and viruses in order to support our immune health. Overuse of disinfectants through incessant application across all surfaces may do more harm than good. Exposure to cleaners, sanitizers, and disinfectants also carry with them attendant health risks, thus should only be handled by a knowledgeable adult, and without the presence of children in the room. For more info on finding out whether you should clean, sanitize or disinfect, head to our article: Disinfecting, Cleaning or Sanitizing? -- Definitions and Distinctions.





Fong, Daniel and Prabjit Barn. “Cleaning, Disinfection, and Sterilization at Personal Service Establishments.” (2011).


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