Today's blog is a Q&A based on yesterday's live webinar on sensor placement in temperature mapping studies. If you were able to join us for that webinar, thank you for being so interactive and engaged!
Modern Rules for an Old Practice: Sensor Placement for GxP Environments
There are definitely requirements to monitor these types of spaces. Depending on the publication, guidance, or regulation you are reading, the particular publication may not specify whether two probes are needed.
Often the guidance is intended for locations that may not be temperature controlled. In my experience, only one monitoring probe is used for uprights and smaller, and the logistics of the use of the small space often makes it unreasonable to place a probe in the actual hot or cold spot. Instead a monitoring probe is placed in a sensible reference location, or the user simply standardizes their probe locations to a single type of location, such as just inside the door.
If your space is large enough to walk into the use of multiple probes becomes possible, but isn't necessary unless there is a significant temperature differential across the unit. For larger spaces, such as warehouses, multiple probes will be expected just given the size of the space, and you may find it useful to place probes in the actual hot and cold spots.
There are no published guidances with specific criteria for placement of sensors in large spaces, especially once the volume of the space is over 20 cubic meters. However, I will give you some basic rules in the webinar to help you in this sort of situation. In a room temperature warehouse, if you use three layers of sensors, with no more than 20 meters of lateral distance between each sensor, you will do fine. This is conservative, but it makes auditors happy.
Yes. In most cases, it just isn't logistically practical to place a sensor in a worst case location without exposing the sensor to damage or using up important storage space in the unit.
The webinar provides guidance on this, but briefly, it depends mostly on the size of the room, but it is strongly impacted by the HVAC organization, how the room is used, and several other factors.
Yes, but not individually. I prefer the ISPE Good Practice Guide to Cold Chain Management for guidance on sensor placement. The ISPE guide considers those publications.
Continual mapping is a concept I really like, but I find it is only practical for large spaces such as warehouses and large cold-rooms. For free-standing chambers and small rooms, the sensor density to do a good continuous map is prohibitively expensive.
I always recommend post-calibration check regardless of the type of sensor used for mapping. VL-2000s are particularly robust. I would think a single point check would be sufficient provided there wasn't a large range of temperatures found during the mapping exercise.
vLog can be used to do mapping and validation that would satisfy the requirements of USP 36 Chapter <1079>. However, I am not aware that <1079> includes any requirements for software that might apply to vLog. In my experience, <1079> speaks more to the types of environments that should be mapped, how sensors should be placed, and the duration of the mapping study.
Before the study I would expect every spot to be a potential worst case location. However, having some experience with similar units might lead you to expect that is directly in front of the cooling units might be a cold area, near the doors might be a warm area, there is probably a warm "dead spot: that gets little air circulation (probably in the back, depending on the cooling unit location).
Doing the mapping study with a sufficient density of sensors will quickly identify the locations of concern.
I determine it based on the risk and sensitivity of the process being monitored. If the items being stored don't cost much, are easily replaced, and aren't sensitive to temperature changes, I would remap infrequently, maybe every 5 years. I could imagine that this might include standard reagents for a QC lab. If the items being stored were expensive, hard to replace, or extremely sensitive, I might revalidate yearly. I could imagine that this might be stability chambers for an expensive and sensitive drug study.
Paul Daniel is the Senior Regulatory Compliance Expert at Vaisala. He 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 also shares his GMP experience through regular blog contributions, webinars, and seminars around the world. Paul’s expertise in the demanding GxP world is applicable to any industry where measurement is critical to product quality. Paul is a graduate of University of California, Berkeley, with a bachelor's degree in biology.