Paul Daniel

Oct 13, 2023
Mr. Panchal –

Thank you for your question. Most people won’t know about BOD incubators, so please allow me to explain it for others who may read this blog answer.

BOD is an acronym for Biochemical Oxygen Demand. BOD testing is a typical measurement of water quality, by measuring oxygen consumption by aerobic biological organisms. BOD testing is usually done at 20C, thus the need for a controlled environment of an incubator. I will admit, I don’t have any personal experience with BOD incubators, so won’t be able to speak to the effects of powering up or powering down a BOD incubator, other than what I have read on the internet which indicates that BOD calibration should be done daily, so that would be an important part of any intermittent operation. But I can speak to the other part of the question, which is the effects on temperature stability of operating an incubator once every 6 months.

Typically, CTUs (Controlled Temperature Units like freezers, refrigerators, etc) are run continuously as they are used continuously for storage. Incubator operation (or stability chamber as well) can be continuous, but it isn’t unusual for it to be sequential, and have the units powered up when they are needed. In my experience, GxP companies use them both ways. Some leave them on all the time, and others are okay with turning them off for short periods (a few days to a week) when not being used. What is different with the question asked today about the BOD incubator, is that the period between uses is 6 months. The amount of time out of use matters with any kind of equipment.

I am tempted to make a comparison to an automobile. I am okay with not driving my car for a few days, and I have a reasonable expectation (based on experience) that my car will operate just fine after a week without use. But if I did not drive my car for 6 months, I would not expect that my car would operate normally. At the very least, the battery would need to be recharged and maybe replaced. So, some sort of maintenance and refresh would be needed for an automobile before I would expect to be able to use it reliably and safely after not being used for 6 months.

So back to the incubator. 6 months seems like a long time for an incubator (or other piece of equipment) to be out of use and still have an assumption of safe and reliable use. I would expect, at the very least, that when the incubator was powered back up after 6 months of disuse, there would be some structured and documented tests to show that the incubator was operating and performing as expected, from a temperature stability point of view. Remember, equipment like incubators is typically remapped every 3 years anyway. If using it every 6 months, you really can only expect to get 5 use cycles out of the device before it is time to remap it. Another way to say that is 20% of the times that you turn it on, you should expect to map it again, even if everything was working just fine and there were no negative effects from the period of disuse..

Leaving the equipment on will cost more energy (though not much because the target temperature is only 20C), but it will save you some work at restart. For follow up, I would speak with the manufacturer of your BOD incubator to determine what might change when the incubator is turned off for 6 months.

Your actual question was if there was a “requirement” for the incubator to be run continuously. There is not a specific requirement that an incubator needs to be run continuously. But there is a requirement that you can prove that your incubator is capable to control temperatures within the required specifications, and you introduce some risk when the equipment is powered down for 6 months. GxP regulations, in general, would require that you address this risk.

Best Regards,

Paul Daniel
Sr. GxP Regulatory Expert