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The Importance Of A Battery Backup For Temperature Sensors

Apr 25, 2013

The storage of vaccines and other biopharmaceutical substances is an important issue with many moving parts. From production to storage, the links of the cold chain are responsible for maintaining operational temperatures throughout transportation and distribution. Still, once these precious items reach their destination, fault-tolerant storage is a critical issue to address. Frankly, many of the sensors in today's market provide excellent operational capability with AC power, but are not typically supported by a backup battery. What does this mean for the storage of vaccines and pharmaceutical drugs, and how might a business benefit/mitigate disaster from a temperature sensing device with a supplemental battery backup?

In the realm of vaccine storage, this concept of "continual" monitoring is extremely important. As we've outlined in previous blog posts, temperature dictates the operational effectiveness of a vaccine. While heat damage is the most commonly cited concern for the cold chain, temperatures that are too low can cause significant problems as well. NIST.gov highlights this problem in a past systematic literature review, noting that,

"Damage from accidental freezing can result in potency loss for freeze-sensitive vaccines such as diphtheria, tetanus, pertussis, liquid Haemophilus influenzae type b (Hib), hepatitis B, and inactivated polio virus[2–6]. However, cold chain practices tend to prioritize protecting vaccine from heat damage, often at the risk of exposure to freezing temperatures. As a result, accidental freezing of vaccines is a largely overlooked problem, yet freeze-sensitive vaccines represented over 31% of the US$ 439 million UNICEF spent on all vaccines in 2005."


Given that, how important does a backup battery become to ensuring safe storage temperatures? The answer is obvious; ensuring that temperature sensors have a backup power source is the ultimate safeguard against power outages. During outages, vaccines can experience a variety of temperature changes (of which may compromise the effectiveness of the vaccine). The missed readings during an outage may hold important data insight into the changing nature of vaccine temperatures, and may further indicate a problem. While a 3-hour power outage may seem insignificant to the temperature on the surface, it actually represents a large window by which vaccines can be rendered damaged or inactive.

Even if power is restored and storage units are able to restart their cycles, the equipment downtime endangers the effectiveness of the vaccine. By using a temperature sensor with enabled battery backup, these "empty windows" of missed readings are eliminated. As a plus, these sensor types can be configured to send "loss of AC power" notifications, indicating that the device has shifted to battery power. This alert, by itself, is both a safeguard and a vital communication stream. Employees or handlers will be aware that power has been lost, and that the clock (to transfer vaccines to a generator-powered storage) has begun ticking. 

While the sensor market is crowded with a variety of sensor types, alert capabilities, and device features, such backup battery devices are difficult to find. This represents a significant problem for cold chain monitoring, wherein the "downtime windows" that result from a power outage are too crucial to be ignored. Knowledge has said to be power, and in this case, the knowledge (or alert) of lost power is a truly powerful tool for vaccine storage handlers and the cold chain distribution network as a whole.


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