While transporting perishable products, it has become increasingly important to produce records of the temperatures, and in certain cases, humidity, to which the cargo has been exposed to. This article provides some details on humidity and temperature logging in logistics and explains the equipment options available. At the end of this article, the reader will be able to appreciate the reasons for recording humidity and temperature data, and better understand the equipment available and how it can be employed.
Individual sections address:
- Background to temperature monitoring
- The cold chain
- Cost and liability issues
- Recording temperature and humidity
- Portable electronic temperature and humidity data loggers
- EudraLex/FDA compliant temperature loggers
- Loggers carried by OMEGA
Background to Temperature Monitoring
At room temperature, many products deteriorate rapidly and as the temperature increases the rate of deterioration becomes much faster. Fruit, fish, meat and other similar food items cannot be transported over long distances without refrigeration. In some cases, chilling to 13 °C (55 °F) is adequate for produce to be sold fresh (or produce that does not freeze readily) such as bananas. Another example is egg, which requires humidity control. There are other products that have to be frozen to prevent deterioration. The same holds true for many medical and pharmaceutical products. According to the Healthcare Distribution Management Association, about 10% of drugs are sensitive to temperature change. Blood products and vaccines are further examples of medical products that require stringent temperature control, albeit these are occasionally exposed to freeze-drying through the lyophilization process.
The demand for temperature control extends beyond products meant for human consumption. Certain coating materials or specialist paints get damaged when exposed to low temperatures, and during transportation other chemicals need to be maintained within strict temperature limits.
Another key area of concern is the transportation of antiquities and works of art. For these products, humidity can pose a greater problem than temperature because it can lead to mold, particularly if the two are combined.
The Cold Chain
It is very important to maintain perishable products at a controlled temperature, from point of origin to delivery to pharmacy or retailer. This is referred to as the “cold chain” by the logistics industry, and covers both “reefers” or refrigerated containers as well as distribution centers, warehouses and the final holding or storage areas.
However, the risk of failure is always present throughout this chain, which means cargo is likely to exceed safe or acceptable temperature levels, even if only for a short time. For instance, a truck may stop in desert heat where there is no power, enabling the reefer temperatures to rise. Once power is restored, the container’s temperature returns to its original condition, but the product is already damaged.
Cost and Liability Issues
When cargo shipment like those listed above is exposed to temperatures beyond the permissible limits, it can get damaged. This is obvious in some cases, such as with bananas, but in other cases like the transportation of vaccines, it may not be obvious that damage has occurred and that the vaccine has become ineffective. For certain products, going beyond the prescribed temperature, even for a short time, can considerably reduce shelf life, resulting in substantial costs when it cannot be sold.
Often, organizations contracting to deliver perishable products specify the acceptable temperature range, but even if it was shown that the product was subjected to conditions outside of those contracted, proving where it occurred, and thus responsibility, will be very difficult. The solution is to create a time-based record of the temperatures experienced.
Recording Temperature and Humidity
Around 1780, the maximum-minimum thermometer was developed which, for a long time, was the only means of capturing the lowest and highest temperatures observed over a given period. Apart from using mercury as the expansion medium, the thermometer had another weakness - the absence of time record. Therefore, while max-min thermometers could be included in a fruit shipment, there would be no way to find out when, or for how long, the peak temperature was experienced. Without this data, it becomes difficult to determine the responsibility for any spoilage.
The same rule applies to humidity indicators. Different types of humidity indicators are available, most of which employ some color-change effect to demonstrate either the current humidity or the peak humidity experienced.
Though in the case of the max-min thermometer, no time record is available to support claims for negligence.
OM-90 Series Data Logger
Portable Electronic Temperature and Humidity Data Loggers
Advancements in digital electronics led to the advent of portable data logger for shipping. These electronics are powered by battery and are compact enough to be placed adjacent to or among perishable cargo where they log the humidity or temperature. They can be configured to create a record as infrequently as hourly or as frequently as every second. Some digital electronics even allow an interval of 18 hours. The only limiting factor is the number of data points that can be stored, which means if set to record at a high rate they will quickly run out of space sooner.
Humidity is ±3.0% RH and temperature accuracy is typically ±0.5 °C. Both can be programmed to commence subsequent to a delay period and once they are recovered they can be plugged in to a system and the data can be transferred into Excel® or any other package for further analysis. When minimum or maximum limits have been exceeded, alarms can be set to illuminate LED indicators and any potential problems can be detected instantly.
EudraLex/FDA Compliant Temperature Loggers
Under the CFR 21 standard, the FDA requires that drugs be stored at correct temperatures. Electronic records are admissible under 21 CFR Pt.11 (Within the EU, EudraLex Volume 4, Annex 11), and data loggers can be employed to show compliance with this standard. In addition, the FDA expects that temperature monitoring will be performed during the lyophilization process when used on materials of a biological origin.
OM-CP-LYOTEMP Data Logger
Loggers Carried by OMEGA
OMEGA provides a range of temperature and humidity loggers for shipping and other applications. The compact OM-90 series cover a humidity range from 0 to 100% RH and temperature range from minus 30 to 80 °C (-22 to 176 °F) and can log approximately 65,000 measurements.
The OM-CP-EGGTEMP series are specifically meant for monitoring the transport of eggs. They are shaped in the forms of an egg for easy inclusion in shipping packages and can function over a temperature range of 0 to 60 °C (32 to 140 °F) and humidity range from 0 to 95% RH. More than 32,000 readings can be held in memory.
Since very low temperatures are required in the lyophilization process, the OM-CP-LYOTEMP data logger was developed with an operating range of minus 60 to 75 °C (-76 to 167 °F). It can be connected to a system through a USB docking station, and the dedicated software has features such as mean kinetic temperature recording. For situations where multiple data sets required, such as when a number of freezers are employed for storage, OMEGA provides the four channel OM-DVT4. This has an LCD display and accepts inputs from three external probes along with the internal sensor, indicating all four temperatures along with sample status, memory remaining, alarm status, and other settings.
Single use temperature recorder provides another approach for cold chain temperature monitoring. OMEGA provides both the OM-21 and OM-CP-TRANSITEMP-EC data loggers. These are inexpensive and compact, and can be loaded in with the cargo at the point of origin and recovered on final delivery. The operating range of these loggers is minus 20 to 70 °C (-4 to 158 °F) [minus 30 °C (-22 °F) for the OM-21] and as with the other loggers illustrated, the data collected can be conveniently transferred to a computer for review. (In fact, the OM-21 prepares the data in pdf format and behaves similar to a USB flash drive).
OM-CP-EGGTEMP Data Logger
OM-DVT4 Data Logger
OM-CP-TRANSITEMP-EC Data Logger
It is important that products ranging from chemicals and vaccines to works of art and eggs are transported under regulated environmental conditions. Portable humidity and temperature loggers offer a time-stamped record of the conditions faced in transit and serve as a useful source of proof should claims be made for damage/loss
In the pharmaceutical industry, FDA regulations mandate that drugs be stored at proper temperatures and lyophilization should be carried out under regulated conditions. Logging of humidity and temperature provides proof of compliance, and if conducted correctly, will comply with FDA requirements for electronic record-keeping.
The new types of humidity and temperature loggers are inexpensive and compact, making them easy to include with transport or shipping packages. Batteries are long-lasting and accuracies are typically within 0.5 °C. Such technology is allowing significant growth in temperature logging, ensuring the safety of supply chains and products meant to maintain human health.
This information has been sourced, reviewed and adapted from materials provided by OMEGA Engineering Ltd.
For more information on this source, please visit OMEGA Engineering Ltd.