Larsen recommended that device manufacturers pay attention to materials and adhesives, and keep samples below 55º C for their accelerated temperature. He added, "Humidity has nothing to do with aging—it confounds the entire process and can cause reaction between materials that would normally never happen. If there's a need for humidity in testing, the selection of the correct materials is critical." He recommended referencing the F1980-07's new revision for guidance on humidity. Other Larsen tips:
• Understand that seals may get stronger over time. Most of the packaging materials used today are very robust, and can readily maintain package integrity for many years.
• Know your distribution environment. Canned tests may be more severe than the actual distribution environment.
• Inspect your sample during testing if possible--before and after sterilization—to learn where a failure happened.
• Consider that sample sizes may open a can of worms. Ten boxes of one dozen are not 120 samples, they are 10 samples. A sample is what goes out the door, what is introduced into interstate commerce. If a single device is sold as one, or in a quantity of one dozen, as a 24-pack, as a gross, as a pallet, you have five different products and five different packaging systems. If you choose one of those as a "worst-case" design to test and not test the others, you must justify why.
• Understand what stresses your sample will be subjected to during distribution. A pallet doesn't withstand nearly the beating as one package going through small-parcel distribution on its own. A multipack package system has different stresses on the contents than that of a one-each.
• Realize that sample sizes are a business decision because they can be quite expensive and tough to get. In general, 30 is a number that the FDA finds acceptable for accelerated aging, but if you sell 150 high-priced items a year, 12 might be a reasonable amount to sample in accelerated aging tests. Whatever your sample size is, you must document the rationale you used in selecting it.
--By Jim Butschli, Editor