What is ATP Testing? 

Adenosine triphosphate (ATP) testing measures the organic matter — not bacteria or viruses — on a surface, and it is commonly used to monitor/improve cleaning techniques. ATP has primarily been used in the food industry, but other sectors are embracing the practice for its ability to detect the presence of otherwise invisible particles on surfaces.  

What’s Needed to Test? 

To conduct ATP testing, users need three things:  

• Test swabs — which usually come in packs of 100  

• A luminometer— which gives a reading in relative light units (RLU) that determines the probability of pathogenic biofilm on the surface 

• A test surface that is roughly a four-by-four-inch space  

What Are the Steps to ATP Testing? 

Once the surface in question is set, users use the test swab handle (bulb) to apply equal levels of pressure across the entire surface for no more than five seconds. Experts recommend applying enough pressure so that the swab bends lightly while rotating, but to avoid touching the shaft of the swab as it can compromise the accuracy of the sample.  

Once the swabbing is complete, add the swab back into the tube and squeeze the bulb handle twice — releasing the test liquid down to the bottom of the swab, then shake for five seconds. Once this is complete, the tube can be entered into the luminometer. After 15 seconds, the luminometer will provide the ATP reading, or RLU. Generally, the most accurate results will be produced when the ambient temperature ranges between 70 and 72 degrees Fahrenheit. Avoiding sunlight is also ideal during testing, according to research from Kaivac, Inc.  

What is a Good RLU Score? 

Scores can vary by facility type, but Z Bioscience provides a template that can serve as a good starting point. An ATP reading of zero is incredibly rare and indicates just 0.0001 percent of pathogenic biofilm. A reading of 10 equals 0.1 percent; 30 equals 2 percent; and above 100 equals 50 percent. Regardless of the facility, a reading over 100 would be a definite cause for concern and a telltale sign that touchpoints aren’t being sufficiently cleaned — or overlooked altogether. Meanwhile, a score above 10 is classified as dirty in foodservice, while more conventional facilities such as hotels and office spaces should consider any score under 30 to be acceptable.  

Once a reading is completed, it’s important for BSCs to document each test. The easiest way to do so is maintain a spreadsheet where the surface, RLU score, and initials of the tester are logged. Spreadsheets can also include templates for different standards depending on the surface. For example, the Kaivac report notes that passing RLU score for a sink would be lower than for a floor.  

Key Spots for ATP Testing 

Experts recommend considering a few things when selecting surfaces for ATP testing:  

• Look at conventional touchpoints like elevator buttons and door handles. 

• Target surfaces that were most likely overlooked by cleaning staff such as work desks, keyboards and other surfaces linked to personal workspaces.  

• Focus on indirect contact areas such as surfaces where contaminants can be drained, splashed or dropped into.  

• Look at hard-to-clean contact areas, especially if cleaning crews are required to cover areas of large square footage in limited amounts of time. Examples include nozzles, hoses, cracks and joints, and O-rings.  

Key Caveats

While ATP testing can reveal missed or under-cleaned surfaces, it has some notable limitations. Though it reads biofilm levels (which equate to the likeliness of pathogens), it’s not a strong indicator for viruses since they aren’t living cells and ATP is only found in living organisms.  Perhaps the biggest caveat to ATP, however, is its unreliability to be used in facilities that utilize disinfectants, according to a study from the National Center for Biotechnology Information. The most probable cause is that disinfectants contain chemicals that interfere with the accuracy of ATP measurements. 

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