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How Do You Know a Surface is Clean and Disinfected?

With the recent COVID-19 pandemic we are fielding calls, "How do I know something is clean?"  The answer is really pretty simple... you test it.  We have testing tools available from the healthcare and food industries to know if something passes a "clean" test.  The primary tool used for testing is called an ATP meter.

The CDC sets healthcare guidelines for ATP testing, and we don't have to use those in all situations.  But they give us a idea of where to start.  And lets face it, our schools and office buildings are not going to be cleaned to healthcare standards, but we can use the testing tools to monitor the cleaning levels and then use the baselines to determine if something is sliding out of the ranges that have been set for a building or a district.  We know where cleaning needs to be improved with sampling of the environment.  Generally we use an ATP meter to randomly test from a set of predetermined human touch points and collect statistical data from the testing.  It gets graphed and reports are generated as needed.

How does an ATP meter work?  It is really cool science, but we are not going to go into all the details in this blog.  But an ATP meter measures Adenosine Triphosphate (shortened to ATP) and it is present in all organic material and is the universal unit of energy used in all living cells and even things like viruses.  The meter uses a disposable surface collection swab, and when mixed with two chemicals gives off light photons in direct proportion to the amount of ATP found on the swab.  The more light, the higher the number (called an RLU - Relative Light Unit) that is displayed on the meter.  A surface will have a low RLU if it doesn't have much ATP.  And a very high number with a lot of ATP on it.  The ATP meter DOES NOT indicate the presence of harmful pathogens, it simply gives a number representing the presence of living or dead organic material.  A yogurt will yield a very high number, just as a sample of COVID-19 would.  The idea with the meter is that to have a clean surface you want ALL organic matter to be absent from the surface.

Some average numbers we've found from testing random non-healthcare items:
Cell phones - 5,000 -20,000 RLU's
Toilet seat -1,800 RLU's
Countertop - 5,000-25,000 RLU's
Desk phone - 1,700 RLU's
Door knob - 1,500 RLU's
Cleaned metal railing - 118 RLU's
Cell phone cleaned with quality disposable disinfectant wipe -228 RLU's
Cell phone cleaned with popular name branded disposable wipe - 1,500 RLU's

ATP Meter readings for surfaces

The CDC recommends a patient room achieve 80% passing scores with RLU's of 250 or less.  500 RLU's for a nursing home.  Anything run through a sterilization process - less than 50 RLU's.

How sensitive is the ATP meter?  A quality meter such as our Neogen AccuPoint unit will detect the breath of someone trying to dry a surface off to speed up a test.  We learned we had to use a paper fan to dry a surface off for an accurate reading and couldn't use a towel of any kind because of ATP found in the towel from natural fibers skewed the results.

From random sampling around offices we've found it is better to eat your food from an average office  toilet seat, than your keyboard and seriously better than allowing it to touch your cellphone.

Our testing of a very popular name brand of disposable wipes found them to lower the ATP reading, but failed to disinfect the surface to healthcare standards.  Watch the video results of this test.  We were shocked at how poorly they worked.

To purchase an ATP meter please review the product page for the AccuPoint ATP Meter