By Chris Bennett

It is hard to describe what’s happening during the COVID-19 outbreak without seeming dramatic, but this is uncharted territory to say the least. Medical facilities have a head start in understanding how to control and kill pathogens, but what about the rest of us? Which antimicrobials sanitize and which ones disinfect or sterilize? Is there a difference? What rating system should be used to help select products that kill viruses?

With so many companies moving into the cleaning supply field in a short time, it can be hard to know which products are safe to be around humans and at the same time also reduce the chance of infection from harmful pathogens.

Sanitizing versus disinfecting versus sterilizing

As with terms like cement and concrete—“sanitize,” “disinfect,” and “sterilize” are often used interchangeably despite describing three different types of antimicrobials. According to the EPA, antimicrobials are products that “destroy or suppress the growth of harmful microorganisms such as bacteria, viruses, or fungi on inanimate objects and surfaces.”

Sanitizing describes the act of reducing bacteria on a surface. It is common to have sanitizers used in kitchens and food preparation areas. Sanitizers are the weakest type of public health antimicrobial.

Disinfectants are much stronger and will kill and prevent the growth of bacteria and fungi. Some, but not all, types of disinfectants can kill viruses like HIV, respiratory syncytial virus, and coronavirus varieties. Read product labels closely to understand what to use them for and best application practices. Disinfectants are the most commonly used antimicrobial in the medical industry or where preventing bacteria and virus growth is important in keeping facilities open and operating in a healthy fashion. They should not be used on surfaces that come in contact with food.

The strongest of the antimicrobials is categorized as a sterilizer. In addition to killing live fungi and bacteria, they can also reduce the spores that create new microbes. Training and certification are usually required to handle and use these products.

Some products are a hybrid of sanitizer and disinfectant. These are useful when you not only need to disinfect an area, but also need to clean away material and residue that provide breeding grounds for new bacteria and viruses.

It also is generally a good idea to have products that are non-film forming unless there is a specific reason film would provide a benefit. The film left behind with some products may actually produce an environment that more easily captures organic material and may facilitate and encourage microbial survival. If a product claims to be viricidal, make sure it has current registry by the EPA.

Sterility assurance level and log kill rates for antimicrobials

“Sterility assurance level” is a system of measuring the probability of survival for biological matter such as a virus. As with all probabilities, the measurement is always somewhere between zero and one. This is because it is not ever possible to prove the survival of an individual microorganism is zero. Instead, the highest percentage usually ascribed to a product that kills germs, viruses, etc. is 99.99%.

In the cleaning world, the rating system for measuring a product’s efficiency in pathogen reduction is referred to as a log kill rate, and this rating can be used to measure the killing efficacy of an aseptic product or process. The following list can aid in understanding the value of each log kill rate level using one million bacteria as an example:

  • A 1-log kill reduces the colony to 100,000 bacteria after a 90% reduction.
  • A 2-log kill reduces the colony to 10,000 bacteria after a 99% reduction.
  • A 3-log kill reduces the colony to 1,000 bacteria after a 99.9% reduction.
  • A 4-log kill reduces the colony to 100 bacteria after a 99.99% reduction.
  • A 5-log kill reduces the colony to 10 bacteria after a 99.999% reduction.
  • A 6-log kill reduces the colony to 1 bacterium after a 99.9999% reduction.

Different log kill rates may be required for different applications. A 5-log kill rate will have a positive impact on killing viruses and is often the minimum standard as part of rehabilitating a facility from a bioburden like COVID-19. However, EPA guidelines may be higher or lower depending on facility type and surfaces where the product is being applied.

The future of cleaning

How the COVID-19 situation continues to evolve will be based on the decisions we make in responding to the demands in protecting public health. With both time and resources limited, it is even more important to make the right decision the first time around.

Many of us have had to reshape our businesses in a matter of just a few days as we confront one of the greatest challenges many generations will ever encounter. We will make advances, and we will make mistakes. Understanding the language around solutions is the first step. Understanding proper use and limitations for antimicrobials is the second.

One would be heartbroken to realize that the products they are using have been ineffective during a time in which supply shortages and no second chances are part of the battlefield. Ultimately, we will solve the coronavirus pandemic by sharing what is working and what is not and by staying engaged with each other in new ways to achieve preventative disinfection measures. In doing so we will come to be stronger together.


Chris Bennett, CSI, is a construction consultant for commercial projects in North America. He specializes in planning and constructing for whole facility life cycles, taking maintenance and cleaning into account during design development. He can be reached via email at [email protected].