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Healthcare Home  ATP Cleaning Verification System→ 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 cleaning verification 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 cutoff 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 thoroughly cleaned.
  • 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 RLU results, download the System Implementation Guide.

graph 1 passcautionfail

Default RLU limits on the 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. 

Default RLU limits no caution

The default limits of 10 and 30 RLU are based on actual limits used in OR's, ICU's and Sterile Services.

Continue reading for limit recommendations in other hospital areas.

Set the best RLU limits for the areas you're testing.

Hygiena offers recommendations for Pass & Fail limits based on clinical experiences and current literature. For details, download the Technical Document on Establishing RLU Pass/Fail Limits here. We recommend you keep a copy of this document in your records for auditor verification. 

General Area

Patient Rooms

Operating Rooms


Labor & Delivery

NICU/ Nursery

Public Areas

Food Service

Sterile Services

Mobile Workstations

Pass Limit










Fail Limit










Calculating custom limits for your locations. 

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


identify icon

Identify test points in your facility. Use the Centers for Disease Control (CDC) checklist as a starting point. Include other touch points in your facility that could potentially be vectors for infection. 

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Clean locations to the highest standard of clean.

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Test each location 5-10 times. For large locations, such as a patient tray table, tests can be collected from different 4x4 inch areas on the table. For smaller areas, such as a call button, 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, 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 Setting Custom RLU Limits Guide for more details, or download the RLU Limit Calculator for Healthcare to automatically calculate your custom limits.


Programming limits in your meter. 

If all locations in your facility will have the same Pass and Fail limit, you can manually adjust the Pass and Fail limits in the SystemSURE Plus luminometer by navigating to 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 software here.

one hand use systemsure

Periodically revisit limit settings for continuous improvement. 

Periodically revisiting your Pass and Fail limits will help to improve your environmental monitoring program and make sure your facility is always cleaned to the highest standard. If you find that your are obtaining frequent Caution and Fail results, you may need to troubleshoot cleaning 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.