Medical device blogger addresses technical questions

Validating heat sealers, dye penetration and burst tests, the consequences of designing packaging late in the product design process, and sterilization issues are among the topics that Jacob Kearns has answered in the past year on his "Medical Device Blog." Kearns is an engineer for a medical device company. Differing points of view may be shared on this blog.

Question: What are the steps involved in validating heat sealers?

Answer: First, make sure your heat sealer is calibrated; then determine the settings you want to operate at for a particular bag or pouch. Once you have determined the settings, heat-seal enough samples at those settings to get at least 30 peel test (ASTM F88) samples. Then peel test those samples to ensure they meet your minimum requirement, usually 1.0 lb/inch, but I've seen 0.75 and 1.25 lb/inch as requirements, too.

All the heat sealers I've seen allow you to set precise time and temperatures, for example, at 280ºF and 1.0 seconds (if you don't have a digital heat sealer, buy a new one). The FDA seems to like to see validations at the range of allowable conditions--a little tricky if you have only one allowable setting, but to be on the safe side I think you should also include one step up, 281ºF and 1.1 seconds for example, and one step down in the validation, and peel test 30 samples of each. If you have more variables, such as release temperature or pressure, you will need to also address them. It is important to note that your heat-sealer validation is only good for the bag or pouch you tested and the heat sealer you tested. If those change, you will need to revalidate.

Question: For ethylene oxide degassing, how much porous surface area should my packaging have?

Answer: Use the largest porous area (usually Tyvek® or paper) you can. If possible, use porous material on one entire side of the pouch. Having more porous surface area can significantly reduce degassing time; however, in most cases other packaging considerations are more important.

Question: How can I avoid dye penetration test (ASTM F1929) failures?

Answer: Don't seal porous materials if you don't have to. The seal between your porous material and the film is the one most likely to fail a dye penetration test with either a true or false positive. With gamma or some other types of sterilization you may not need a porous section in your pouch. A header bag reduces the exposed seals and a tray can eliminate them altogether. Also, use properly sized pouches and boxes, lay the pouch flat in the box, and avoid standing them on end so the weight rests on the seal. Finally, train manufacturing and quality personnel to avoid wrinkling or folding the seals when they handle the packaging.

Question: Is the burst test (ASTM F1140) required for packaging validation?

Answer: The FDA and ISO 11607 do not require specific tests or test conditions. The burst-strength test will measure the weakest seal strength. I feel the peel test is a more accurate test that measures approximately the same thing. Doing both tests is common, although not specifically required.

Question: What are the consequences of designing packaging late in the product design process?

Answer: Waiting until the last minute to design packaging is often necessary due to product changes. In my experience, it does not cause too much trouble if you can use fairly standard packaging. If you absolutely have to, you can use off-the-shelf pouches and boxes. Custom, properly sized pouches and boxes will make your validation more likely to succeed. There are companies that will make these quickly. If a mounting card is required, it will have to be custom-made, but the lead times are relatively short, as long as you know what you want.

Question: Should I sterilize a master carton or the final product box?

Answer: I have been part of devices using both strategies and I have to say I much prefer using a master carton than repackaging when the shipment gets back from the sterilizer. While sterilizing the final product box often sounds better, and is much easier from a QA point of view, I've found using a master carton leads to less rejects and overall a much better-looking final product. Additionally, the master carton gives you more flexibility, which is important during the early stages of a project--you don't want to be stuck with poor packaging because you'd have to revalidate sterilization if you changed it.

Disclaimer: Jacob answers each question to the best of his ability, but does not claim to be an expert. He recommends using his Q & A as a starting point for your research to develop your own policies. His blog can be found at If you have a different point of view and wish to share it with Jacob, log onto his blog. Healthcare Packaging may publish any dialogue resulting from this article.