Recently FDA regulations including HACCP, various CFR code of federal regulations, and the push to eliminate wasted time and money in fixing temperature related product failures has made Temperature and Temperature/Humidity Mapping an integral aspect of any warehouse operation.
Inadequately controlled environments can lead to ineffective medicines, spoiled produce, damaged materials and frequent critical equipment failures. This all ads up to wasted dollars. Fortunately the cost of monitoring large warehouses has dropped significantly over the years as temperature and temperature/humidity sensing technology has become more accurate, easier to use and more affordable.
Whether you are concerned about maintaining a consistent temperature in a 5,000 or 500,000 sq. ft. warehouse, you’ll want to make sure that you are using the right tools for the job and that you’re using them correctly.
In this guide, we will discuss best practices for mapping temperature in large spaces.
Planning Your Steps:
Mapping is not a one-time job, but an ongoing process that takes into account changes in seasons, HVAC/R modifications, warehouse layout modifications and any other significant changes to the warehouse environment. Proper organization and documentation are critical in maintaining compliance and consistency.
Step 1 – Determine Critical Mapping Points
Step 2 – Determine Sample Rate
Step 3 – Establish Data Logger Criteria and Select
Step 4 – Place Data Loggers at Pre Determined Points
Step 5 – Retrieve, download and evaluate Logged Data
Step 6 – Document Processes and Repeat
Step 7 – Data Logger Maintenance and Calibrations
Step 8 – Remediation
Step 1 – Determine Critical Mapping Points
Problem Locations:
Large open spaces present a considerable challenge when working to maintain a consistent temperature or temperature/humidity level. Problem spots include: • Areas near the ceiling or exterior walls may stay warmer or cooler in response to temperatures outside.
- Temperature levels stratify due to the fact that warmer air rises.
- Temperatures will tend to be higher near heaters. If fans are undersized or improperly placed they will be incapable of mixing the heated air effectively.
- Racking, shelving and pallet storage areas may create “hot spots” by obstructing air circulation.
- Doors that are left open will affect temperature conditions.
Additional Locations:
In addition to problem spots logger placement is also critical for the following locations:
- HVAC outputs
- Exits to unconditioned spaces (loading docs and staging areas)
- Outside (to compare outside temperatures to internal temperatures)
- High, medium and low locations in the general storage area
Spacing:
Studies have shown that a spacing of every 100 to 300 feet in an open warehouse plan, without walls to block airflow, is adequate enough to accurately represent readings that are meaningful. A distance of greater than every 300 feet may yield data that does not accurately reflect conditions in the warehouse space, while spacing data loggers closer than every 100 feet will result in extra data that adds no value while creating extra work.
Determination of critical mapping points should include all potential problem spots in addition to the normal storage area. Be sure to space the critical mapping points in an evenly distributed grid using every 100 to 300 feet as your spacing guide.
Step 2 – Determining Sample Frequency
The key to determining sample frequency is to not take too many or too few samples. Too many samples will create too much data making analysis cumbersome and difficult. Too few samples will not adequately represent changes in the warehouse environment. In most warehouses, one temperature or temperature and humidity sample every 15 minutes should adequately evaluate temperature trends.
If you think you need to take readings more frequently, consider the following:
Scenario 1
10 data loggers sampling every 15 minutes for 1week will provide 6,720 sample points.
Scenario 2
10 data loggers sampling every minute for 1 week will provide 100,800 sample points.
Scenario 1 will provide the same general results as Scenario 2 with 1/15th of the data and much less time spent analyzing logged data.
The key here is response time. Most temperature data loggers take at least a minute to respond to changes in temperature, and in a space as large as a 50,000 sq. ft. warehouse, most changes will happen very slowly over several minutes, making frequent sampling unnecessary and wasteful.
Step 3 – Establish Data Logger Criteria and Select
Temperature and Temperature/Humidity Data Loggers come with many features. The goal is to select the data logger that will most effectively monitor your warehouse. Key features you should consider are:
- Data Capacity: Data Capacity determines how many readings or sample points can be taken by a logger before memory is full. The more sample points a logger has, the more readings it can store.
- Sample Rate: The frequency in which samples are taken. The logger should feature user selectable sample rates.
- Monitoring Range and Accuracy: Be sure to select a data logger with a temperature range that can monitor temperatures even in the most extreme of cases. Don’t pay extra for accuracy you don’t need. +/-2oF and +/-2% RH should be adequate for most warehouse mapping situations. For refrigerated storage areas or locations requiring tighter tolerances, data loggers with an accuracy of +/-.5 oF should be selected.
- Size: Make sure the logger will fit in your selected locations. Some loggers are as small as a quarter making them perfect for tight locations or when you don’t want them to be noticed.
- Networking: Ethernet connectivity lets you view and download logged data and modify logger settings from your PC on any logger connected to your Local Area Network. These are perfect for smaller warehouse locations where critical items are stored and more frequent temperature readings are necessary.
- Battery Life: Make sure the battery life is long enough to last between mapping sessions. Many data loggers feature battery life between one and five years. More than enough to last through several mapping sequences.
- Calibrations: Be sure to purchase your data logger from a manufacturer who is A2LA accredited, NIST traceable, ISO 17025 compliant and can provide calibration services. The data loggers should be calibrated at least every 12 months.
- Software: Make sure the data logger software is easy to use and that you can export data into Excel for easy mapping of Mean Kinetic Temperature
Be sure to purchase at least one data logger for each location.
Step 4 – Place Data Loggers at Pre Determined Points
Be sure to document the location of each data logger and label each data logger to ensure that it is repeatedly placed in the same location.
To ensure consistency practice the following rules:
- Using the data logger software, name each logger by its location.
- Label the outside of each logger by its location
- Label the exact spot where the data logger should be placed by the data logger’s location name.
- Create a physical map with all data loggers marked by name
Step 5 – Retrieve and download Logged Data
Once the loggers have been placed and data has been collected, collect the data loggers and transfer the logged data to your PC.
The logged data can now be exported to Excel where Mean Kinetic Temperature can be calculated.
Mean Kinetic Temperature is a calculated fixed temperature that simulates the effects of temperature variations over a period of time. It expresses the cumulative thermal stress experienced by a product at varying temperatures during storage and distribution.
The formula for Mean Kinetic Temperature is as follows:
In addition to calculating MKT it is also recommended that Min and Max temperatures should be monitored carefully and that the location and the time of day at which they occur should be recorded. Any trends should be investigated.
A free program to calculate Mean Kinetic Temperature is available at: www.stabilitysystem.com
Step 6 – Document Processes and Repeat
Now that you have completed your first mapping, be sure to place the data loggers back in their original locations throughout the warehouse and make sure to document each and every step used.
Step 7 – Data Logger Maintenance and Calibrations
Over time the most robust data loggers can drift causing inconsistencies in recorded data thus requiring regular calibration in order to ensure accurate readings.
It is recommended that each data logger be calibrated at least every 12 months. In addition, it is prudent to request before and after readings when calibrating each data logger so corrections can be made to previously logged and mapped data.
Best practice recommends sending the data logger to a NIST certified calibration facility, and to the original manufacturer for calibration whenever possible.
Step 8 – Remediation
Now that you have your results it is time to fix any trouble spots that show up in your calculations.
Common Fixes:
- Hot Spots: Hot spots are frequently caused by walls or shelving that block airflow and/or inadequately sized fans that are unable to circulate air. Increasing the size or number of fans and removing unnecessary walls or rearranging shelves to promote airflow is helpful.
- Wide Temperature Fluctuations: Frequent changes in temperature in one location can be caused by direct exposure to outside air sources. Doors that are habitually left open, sky-lights, open doc doors and hallways to nonconditioned locations can make maintaining consistent temperatures difficult. Plastic curtains over open hallway or dock entrances will bock much of the hot or cold air from entering the warehouse space.
- Inability to maintain target warehouse temperature. If the overall warehouse temperature can not be maintained, an expert evaluation of the HVAC system is in order.
Conclusion
Temperature mapping can be an extremely powerful tool to aid in regulatory compliance and create possible cost savings via implemented improvements and efficiencies. The key is to carefully analyze the warehouse space to ensure proper placement of data loggers, document logger locations and mapping processes, audit data including having data loggers calibrated on a regular basis and finally making the necessary changes to continuously improve warehouse conditions.
How to calculate no. of data loggers to be installed in a particular area?
Is it similar to the formula (NL=√A) which is used for Non-viable particle count based on the room area in m2?
Please guide.
Regards
Abhaysingh
Abhaysingh,
I do not recommend using a set formula for how many locations to check in during the mapping process. Variables such as HVAC effectiveness, quantity, location and size of shelving or other obstacles within the space, and air flow throughout the space can have significant affects on the how many would be appropriate for a given amount of volume. I have seen several different formulas to arrive a quantity of temperature monitoring points for a given square footage that having widely varying results.
There are consultants who specialize in warehouse mapping. I believe they look at what makes sense for each location based on a variety of weighted factors, not just square footage.
My recommendation is to locate the critical points to be monitored first. Often the critical points will cover much of the area to be mapped or force the rest of the location to be mapped as separated zones within the warehouse.
Hope that helps,
Dan Gawel
Operations Manager
What should be minimum volume require temperature mapping ?
I'm not aware of an industry approved standard for minimum volume to require mapping. If a location is mapping to measure the effectiveness of an HVAC system on a large open warehouse filled with industrial goods then they would have very different mapping requirements than a pharmaceutical storage warehouse with many important but very small separate locations.
Unfortunately, your question isn't an easy one to answer without more information about the application. If there is a documented recognized standard out there that answers that question we at the Dickson company would love hear about it.
Regards,
Dan Gawel
Dickson
Is there a guide where to place the data loggers in the warehouse ?
Yossi,
Our recommendation is to start with any critical control points, places where the temperature maintenance is the most important.
After the critical points are assigned, then select key entry points where outside temperature is likely to enter, locations such as dock doors or refrigerated warehouse entrances.
After entryways are identified, cover the corners or outside edges of the location to be mapped. Corners are often the last place to get circulated air or the most likely to stagnate.
When looking at the remaining area to be mapped, make sure to get multiple elevations.
Spacing requirements between the locations to be mapped vary by location, industry and warehouse layout.
Regards,
Dan Gawel
Dickson
Dickson has any logger with an included MKT software or function?
Thanks
The WiZARD2 Software does have a MKT function built into it. You can find more information on the system HERE.
Do you know of any other site where I can find the MKT calculation for free?
Mauricio,
I looked for a site/program that can calculate the MKT for free and was unable to find one. I’m working on putting together an excel file that you can copy your data in and the file will automatically calculate the MKT for you. I’ll create a new blog post about MKT if/when I have that available.
Thanks,
Matt
The Dickson Company
Hi Matt, appreciate status of the excel file you are putting together. Thanks upfront.
Hello,
I need to know the limits in Tª and HR% in pharmaceutical warehouses and reglamentations.
Can you helpme?
regards
Hello,
More often than not these are specific to your location, company, and/or what you are monitoring. It is best to talk to those who will be auditing your monitoring process to find out the requirements you must meet.
Hello Matt,
May I know how to perform temperature mapping for refrigerator?How many consecutive run required to qualifying the equipment?
regards
Hello Amir-
Sorry it has taken a while for a response…. It is hard to say what the proper number of devices is or where to place each device. This is hard because of a few reasons: 1) Your operating procedure is probably different from the next company’s, 2) the size of the refrigerator is a factor, and similar to number one 3) industry standards might be different and/or have different requirements. My best advice to to check with the body or organization that requires you to document the temperature.
That being said, there are some general rules of thumb that you can follow. Again, you’ll have to check with your regulating body to ensure you are meeting the requirements. General mapping suggestions (pertaining to refrigerators):
- For tall and thin refrigerators, I have heard of customers doing the top, middle, and bottom shelves
- For a double wide refrigerator, I’ve seen people doing the top, middle, and bottom (vertically) of each the left, right, and center (horizontally).
Again, these are only suggestions and anytime you are dealing with sensitive materials and regulations, you should confirm with the regulating body that you are meeting the necessary requirements.
i was able to assemble a quick xls template, i can send to you for review vs yours if you don't mind. regards
I actually just received the document and am writing the blog post this week. Feel free to send over yours and I’ll compare [marketing (at) dicksondata (dot) com].
Sent just now. Appreciate comments, corrections as necessary. Thanks
Where will your spreadsheet be posted? a link to it? Thanks
Brad,
Found a bug in the sheet that made it unusable. I’m currently trying to work it out, but it looks like I may have to rewrite the function(s) a bit. I’ll do an entire post about MKT when I complete it.
-Matt
Hi,
What time frame should the tests run in a Warehouse? Autoclaves are easy as it is a cycle or 3, fridges for a few days. But for warehouses which would be ideal: 1 day, 3 days or 1 week? I cant find any guidance on this either from regulatory sites.
Cheers
Micah
The longer you can run the test the more confident you can be in your test data. The test should be run for a week if possible, especially if the warehouse is not manned 24 / 7 or if it has different HVAC or thermostat settings on nights or weekends then during the weekday.
Dan Gawel
Have there been any studies on temperature differences in warehouse elevation? Low elevation monitor points have always seem feel good to me. I would think as heat energy decreases, the difference in temperature between the low and high elevations would decrease as there is less warm air to rise. Thus the high elevation would reflect the temperature of the low elevation when the warehouse is cold. When the heat energy increases, the opposite would be true and the difference between low and high would be much greater. In this case the high elevation point would measure the worst case high temperature. A study could show us at what temperatures the difference is significant with graphs to apply to each of our different requirements. At normal temperatures for humans, I measure about a 1 degree C or less difference in 25 feet which is not significant, factoring in the difference between the sensor probes (for personal care products anyway). Please feel free to point out where I am wrong or missed something.
Thanks, Mark
.
I’m not aware of any published studies or white papers on how temperature typically changes at different elevations in a warehouse. You are correct that it does typically get warmer at higher elevations then what you would see near the floor of a warehouse. Any successful mapping exercise should include testing for temperature changes at different elevations.
Dan Gawel
Dickson
What does the mean kinetic temperature signify..? What kind of conclusions can I draw up from the results? How do I analyze trends?
Mean kinetic temperature (MKT) is a simplified way of expressing the overall effect of temperature fluctuations during storage or transit of perishable goods. The MKT is widely used in the pharmaceutical industry and is primarily used to ensure the storage and/or transit temperature stays within required limits for the product or compliance to a standard. Trends can be be monitored by comparing data sets over time or under different conditions.
Dan Gawel
Dickson
I have used 50 temp and humidity loggers to map our warehouse. Any ideas where to find a 3D modeling software in order to have better visualization of the data ?
Kind regards,
Steve
Steve- I'm not aware of any 3D modeling software specifically for mapping a facilities environmental conditions. I suspect Autodesk's AutoCAD software is the most likely to have a solution or to support a 3rd party software add-on that might work for you.
Regards,
Dan
So glad to have found this forum regarding temperature and humidity mapping. I have been conducting temperature mapping (of sterilization chambers, storage chambers, stability chambers/rooms, etc.) as part of our company's Good Storage and Shipping Practices requirements for many years already. And now comes another requirement for conducting humidity mapping, especially stability rooms and stability chambers.
I am seeking advise on whether there are really specific guidelines or standard requirements that can be referred to with regards to humidity mapping. For stability rooms requiring temperature and humidity mapping, I agree that mapping for both parameters should be conducted due to the size and uneven distribution/circulation of air and many other factors. However, for reach-in stability chambers with very stable temperature and humidity control, is there really a need to conduct humidity mapping?
Anybody's expert advise will be highly appreciated.
Mardi-
You raise a good question. From what we understand it is very hard to find concrete requirements that instruct individuals in your position what exactly to do. Typically, it is up to the regulating body or agency that audits your company or facility (be it a parent company, organization, or government agency).
So I’ll give the answer no one truly likes: It depends. If you’re audited by someone who wants a reach-in chamber monitored that closely then you should probably do it. If you’re doing this for your company’s own good then you discuss with your team and/or supervisors what goals you’re trying to accomplish in keeping these records.
Hopefully that helped a bit, but please let us know if you have any additional questions.
-Matt
Would like to qualify the finished goods stores is it require humidity control.
Regards
Amit
Amit – We cannot say for certain that you need to monitor your finished goods. I can say that I’ve heard of more and more request to do so from a few auditing agencies. You should talk to the agency that audits your temperature/humidity monitoring data to determine if they want you to monitor your finished goods.
As far as how many loggers you need for the space you described this is another question for your auditor(s). Our general suggestion is to evenly space them throughout the space (both horizontally and vertically).
Hopefully that helped.
-Matt
If storage area size is 6.7 x 2.2 mtr. how much data loggers do i have to place can you justify?
Or is there any formula from which we can arrived at no. of data loggers to be placed?
Regards
Amit
Is it necesssary to compute MKT for stab room thermal mapping which only lasted for a week?
Bliss-
We cannot say for certain whether or not you’re required to compute the MKT for only one week. I’d check with your auditing body or organization to determine their requirement. Sorry we couldn’t be more specific.
-Matt