What's your open door (mapping study) policy?

24/7 remote freezer temperature and door alarming
Paul Daniel, Vaisala
Senior GxP Regulatory Compliance Expert
Published: Oct 20, 2017
Life Science

In this week's blog, answer a question about open door mapping studies and  offer some considerations that may close the issue (and the door).

Hi Paul,

 I have a question regarding open-door mapping studies…

When evaluating data from this kind of study, is it typical to acquire data for informational purposes only, and then evaluate potential impact to contents in storage?

For example, if our stability guidance allows for “short term” excursions, it is difficult to develop a specification.  In your opinion, would it be better to develop the protocol without specs and evaluate the impact of the data after the study? Thanks for your help!

Validation Engineer

Dear M,

Thank you for reaching out!  Let me first say that I am not a fan of open door studies.  They are often included in validation mapping, but don’t actually have acceptance criteria.  If it doesn’t have acceptance criteria, it isn’t validation. If it isn’t validation, it doesn’t belong in a protocol.  I have seen some folks publish a specification for the expected performance in an open door situation (and a power fail as well) so that they could evaluate the open door performance with a pass/fail answer.

What I always come back to with this question is this:  If you have a problem with the door being left open (or, opened too much) then you have either:

1) A training issue (door left open)
2) A process issue (door opened a lot)
3) An equipment issue (door latch doesn’t work well). 

You can’t make these issues go away with validation or a test. Find and apply the appropriate fixes:
1) Train your employees to close doors and check
2) Fix broken latches
3) Buy appropriate equipment for processes that require frequent access.

This is where a good monitoring system can help; it will tell you when there is a problem from a door being open. You can only evaluate your data from a “door open study” if you actually know how long the door has been open, and the only way I know how to do this is with a monitoring system with door contacts.  If you have invested this much in you monitoring system, just use the system to monitor your temperatures, and forget about how long the door can be left open.

This is my experience: typically, people will do an open-door study and keep the information for future reference.  Then in the case that the door is left open, they can go back to the data set and use it in a rationale to explain why the door having been left open for X minutes was, or wasn’t a problem.  It is supposed to be the magic bullet in their OOS deviation investigation/resolution down the road. 

Your stability guidance allows for “short term” excursions, which will be measured likely by your monitoring system.  “Short term” should be “defined as out of spec for a maximum of X minutes”.  Your open door study will show what value the building monitor probe reads at X-minutes open.  How can we develop specifications for that?  We can’t. The best you can do is just do the study without acceptance criteria, and note at which time the various sensors fall out of specifications, and more importantly, what the temperature is for your monitor probe when the first sensors goes out-of-spec. 

Then this monitoring probe value (which is likely in-spec) is the minimum/maximum you are allowed to reach when the door is left open, or at the very least the time at which you officially start timing your excursion, as it would represent the last known time the first deviating location would have gone out of specification.

Please do email again if you want to discuss further!

Paul Daniel

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Webinar Q&A

In our webinar "Vaporized Hydrogen Peroxide Bio-Decontamination in Isolators and Transfer Hatches"  we covered several topics related to H2O2 bio-decontamination. During the webinar we received a lot of questions. Here we offer some of the most common, and most important questions…

Scroll down to review the Q&A...

Could you describe once more what the difference is between RH% and RS%?

Relative humidity measures only vaporized water in the air. Relative saturation measures both vaporized water and vaporized H2O2 in the air.

Read a more detailed explanation in Vaisala PEROXCAP® Sensor for Measuring Vaporized Hydrogen Peroxide, Relative Saturation and Relative Humidity (pdf).

You are also welcome to listen to one of our on-demand webinars on the topic:

Room Bio-Decontamination with Vaporized Hydrogen Peroxide (webinar recording)

Vaporized H₂O₂ Bio-decontamination in Isolators and Transfer Hatches (webinar recording)

What do you mean by traceable H2O2 calibration?

a. Traceable measurement can be related to appropriate measurement standards, generally national or international, through an unbroken chain of comparisons

b. Vaisala’s HPP272 hydrogen peroxide measurement is traceable to the international system of units (SI) through national metrology institutes (NIST USA, MIKES Finland, or equivalent) or via ISO/IEC 17025 accredited calibration laboratories.

What is the difference between sterilization and bio-decontamination?

Definition for sterilization process is: Any chemical or physical process which destroys all life forms, with special regard to microorganisms (including bacteria and bacterial spores), and inactivates viruses. Therefore the terms "sterile" and "sterilization", describe the absence and the destruction of all viable microorganisms.

Bio-decontamination is defined as removal of microbiological contamination or its reduction to an acceptable level.

Main differences between sterilization and bio-decontamination are also explained on our related on-demand webinar called "Vaporized H2O2 Bio-Decontamination in Isolators and Transfer Hatches".

Why is a higher concentration of H2O2 used for food and beverage than for pharmaceuticals?

Typically in food and beverage industry you have continuous process where for example cups or bottles are bio-decontaminated prior to filling in. Typically very high concentration (e.g. 10000 ppm) for a short time (e.g. 8 seconds) is used to provide the required log reduction. The higher the ppm, the shorter can the bio-decontamination time be, in order to provide the required log reduction. Production turnaround time is the most important factor.

Can the probe be re-calibrated by the end user? If yes, please describe the method.

H2O2 is a very unstable gas and it is therefore difficult to make calibration in H2O2 environment. However, if you have, for example, a factory calibrated HPP272, and another HPP272 that you wish to calibrate, you can just compare the measurement results between these two. It is important that these two probes are installed close to each other to make sure they measure the same environment.

We are currently working on an onsite calibration capability for the HPP272 probe with Relative Humidity (RH). I.e. in the future you will be able to calibrate and adjust the HPP272 onsite using any humidity calibrator (for example Vaisala's HMK15) and Vaisala Insight software. With any humidity calibrator and the Insight software you are able to calibrate and adjust both H2O2 ppm and RH.


So in order to reach micro-condensation conditions you have to reach 100% RS?

Your sensor's Relative Saturation (RS) reading will show 100% when condensation starts. Here is a reference to an article that discusses the relationships between humidity, hydrogen peroxide concentration and micro-condensation:

"The Influence of Humidity, Hydrogen Peroxide Concentration, and Condensation on the Inactivation of Geobacillus stearothermophilus Spores with Hydrogen Peroxide Vapor"
Beatriz Unger-Bimczok, Volker Kottke, Christian Hertel, Johannes Rauschnabel
Journal of Pharmaceutical Innovation (2008) 3:123–133 DOI 10.1007/s12247-008-9027-1.

Published online: 8 May 2008 # International Society for Pharmaceutical Engineering 2008.


What is the tolerance for %RH & ppm?

HPP272 is designed for high humidities. It measures humidity from 0% to 100%. The ppm measurement range is up to 2000 ppm. HPP272 is not for safety level measurement. Our accuracy specifications starts from 10 ppm onwards.

Does H2O2 destroy DNA / RNA?

We know that in general RNA molecules are much more sensitive to degradation than DNA. It's also a well known fact that hydrogen peroxide ions cause oxidation of proteins, membrane lipids and DNA. [see Löffler G. and Petrides P. E.: Physiologische Chemie. 4 ed., p. 288, Springer, Berlin 1988, ISBN 3-540-18163-6 (in German)].

We haven't tested the effectivity of hydrogen peroxide against DNA. We would like to recommend to you that you search on the web if there are scientific studies made about H2O2 effectiveness against DNA/ RNA. Or you could make your own studies. Meanwhile, we would recommend other well known ways to destroy DNA and RNA to be sure about the effectivity. Such as UV-light alone or combined with higher temperature and specific chemical agents that are available commercially to destroy DNA and RNA residues. Such agents are typically used for example in PCR (polymerase chain reaction) applications.


Paul Daniel, Vaisala

Senior GxP Regulatory Compliance Expert

Paul Daniel has worked in the GMP-regulated industries for over 20 years helping manufacturers apply good manufacturing practices in a wide range of qualification projects. His specialties include mapping, monitoring, and computerized systems. At Vaisala, Paul oversees and guides the validation program for the Vaisala viewLinc environmental monitoring system. He serves as a customer advocate to ensure the viewLinc environmental monitoring system matches the demanding requirements of life science and regulated applications. Paul is a graduate of University of California, Berkeley, with a bachelor's degree in biology.

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