Setting RLU Values

Example of Acceptable RLU Values for High-Touch Areas:

A study was done on a senior living facility to assess cleanliness with Hygiena’s ATP Cleaning Verification Systems in which over 200 ATP samples were collected before and after cleaning.

Common RLU Values over 50. Set the meter using the values below for example Telephone is 180 so any test higher than 180 should fail  

1. Telephone 180

2. Door Handle 150

3. Refrigerator Handle 80

Common RLU Values under 50. Set the meter using the values below or  use 50 as an acceptable pass   

1. Handles  35

2. Light Switch 30

3. Keypad 40

4. Arm of Chair 50

5. Bathroom Handle 10

6. Grab Rails 15

7. Chopping Board 10

8. Food Contact 25

9. Taps 25

10. Call Button 20 

11. Toilet Seat 45

12. Bedside Table 25

Step 2: Setting RLU Limits and Identifying Test Locations

Your luminometer comes with default upper and lower limits for quantifying results; values less than the lower limit are a “pass”; results greater than the upper limit are a “fail” and results between the lower and upper limits are a “caution”. These default limits of are based on years of data and third-party studies.

Below are examples of RLU limits for each system. We recommend that you determine your own custom limits based on the instructions below and set the machine to either a pass or fail.

Setting RLU Limits

Setting appropriate RLU limits is a fundamental part of a succesful ATP program. RLU limits will be different for each type of surface. Although ATP systems are set with default RLU limits, Hygiena recommends that ”gold standard” limits be determined for each type of surface that you will be testing.

To determine the lower RLU limit: Calculate the average RLU for each location based on 5-10 test results after cleaning intervention. The lower RLU limit should be set to the average of these results.

There are two options for determining the upper limit:

1. Multiply the lower limit by 3

2. Determine the standard deviation from the test results, multiply the standard deviation by 3, and add this to the lower limit.

Note: When establishing upper and lower limits, it is important to take into account the type of surface and its condition. Older, more pitted surfaces (older stainless steel surfaces ) can be harder to clean and get low RLU values than newer, hard-topped surfaces (new stainless steel counters).

Suggested Test Locations

Elevator Button
Door Handles
Light Switches
Keyboard and Mouse
Refrigerator Handle
Common Area Tables
Bathroom Surfaces
Laundry Room Surfaces

Locations on the machine: Test locations are test points, from which you take a sample for testing. These are surfaces that are highly trafficked. An example of a location is “Front door handle”.

Plans on the machine: Test plans are groups of locations that are tested one after each other, grouped together, or tested on a specific day or site. An example of a plan is, “Building 1 – First Floor.” Although not mandatory, Plans are helpful to analyze data when generating reports within SureTrend.

Users on the machine: Users are the people using the luminometer and performing the testing or the people cleaning. An example of a user is, “John Smith”

- How are test results tracked? – Test results can be tracked on your luminometer and software by location, plan, and user. This information allows users to clearly associate results with the specific location, or group of locations tested, and who performed the tests.


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. 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 4 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.