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Food & Beverage Home → Monitoring Systems→ SystemSURE Plus/EnSURE → Setting ATP Pass & Fail Limits


Get started on the right foot. 

Setting the right Pass and Fail RLU limits from the start will set your monitoring program off on the right foot. Watch the video to the left to learn all about setting and customizing RLU limits for your testing program. The information in this video, along with the instructions below, will guide you through each step.


ATP is measured in RLU's (relative light units). 

ATP systems use relative light units (RLU) as the unit of measure for adenosine triphosphate (ATP). Though the ratio of RLU to ATP varies per manufacturer, the greater the ATP, the higher the RLU. The cut-off scores for acceptable or unacceptable RLU scores are called thresholds, or limits. RLU limits enable users to categorize RLU test results as Pass, Caution, or Fail. 

  • A Pass score is indicated by a check mark and means the surface was properly cleaned and is safe for production.
  • A Caution result is indicated by an exclamation point. At your discretion, locations with a Caution result may be recleaned and retested, or monitored for future problems.
  • A Fail score is indicated by an X and should be recleaned and retested until a Pass or Caution score is achieved. 

For more information about corrective actions for Pass, Caution, or Fail results, download the Hygiene Monitoring Guide.

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Default RLU limits for EnSURE and SystemSURE Plus.


Hygiena systems come preset with Pass and Fail limits of 10 and 30 respectively. Any score of 10 RLU or less is a Pass. Scores from 11 to 30 RLU are a Caution. Any score greater than 30 RLU is a Fail.

Default RLU limits

Some users prefer to eliminate the Caution area and set both Pass and Fail limits to 10. Any score of 10 RLU or less is a Pass. Any score greater than 10 RLU is a Fail.

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The default limits of 10 and 30 RLU are based on years of experience in food and beverage industries and published third-party studies. For more details, download the ATP Thresholds Technical Document here.  We recommend you keep a copy of this document in your HACCP records for audit verification. 

Customized RLU limits to fit your specific needs.

Setting custom RLU limits for locations in your facility depends on the following factors:


Surface type.

Easy to clean surfaces, such as stainless steel or new equipment may have lower RLU limits. Hard to clean equipment such as conveyor belts or aged equipment, may have higher RLU limits.

Contact type.

Surfaces that come into direct contact with products, such as conveyor belts or hoppers, should have more strict, lower RLU limits. Indirect contact surfaces, such as control buttons or the sides of a conveyor belt, are less critical and may have higher RLU limits.

Product type.

Manufacturing equipment for short shelf-life and ready to eat (RTE) products should be held to a higher standard of cleanliness and should have lower RLU limits. Manufacturing equipment for longer shelf-life or cooked products may have higher RLU limits since the cleaning requirement is not as strict and potential contamination is less dangerous.

Calculating custom limits for your locations. 

To calculate custom limits for locations in your facility, follow these four steps: 
Identify, Clean, Test, Calculate.

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Identify test points in your facility. These are usually outlined in HACCP, GMP, or SSOP programs. 

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Clean locations to the highest standard of clean. This may include a total production line breakdown. 

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Test each location 5-10 times. For large locations, such as a conveyor belt, tests can be collected from different 4x4 inch areas on the belt. For smaller areas, such as a fill nozzle, tests must be collected over several days after cleaning.

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To calculate the Pass RLU Limit, calculate the average of the RLU scores. 
The average is your Pass Limit for that location.

To calculate the Fail Limit, use one of the following two methods:

1. Multiplication Method: Multiply the average by 3.

2. Standard Deviation Method (preferred for statistical accuracy): 
Calculate the standard deviation of RLU scores. 
Multiply the standard deviation by 3. 
Add this result to the average to get the Fail RLU.

Download the Hygiene Monitoring Guide for more details, or request an Excel calculator for calculating your custom limits.


Programming limits in your meter. 

If all locations in your facility have the same Pass and Fail limit, you can manually adjust the Pass and Fail limits in the EnSURE or SystemSURE Plus luminometer by navigating to the Programs menu and using the up and down arrows to set the Pass and Fail limits. 

To get the most of your monitoring system, and to be able to track and trend test results, use SureTrend software to program locations and customize limits.  Learn more about SureTrend and SureTrend Cloud software here.

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Periodically revisit limit settings for continuous improvement. 

Periodically revisiting your Pass and Fail limits will help to improve your food safety program and make sure your facility is always cleaned to the highest standard. If you find that you are obtaining frequent Caution and Fail results, you may need to troubleshoot sanitation protocols, or raise your Pass and Fail RLU limits. If you rarely obtain Caution or Fail results, you should consider lowering your RLU limits to facilitate a more strict monitoring program.