This small little thing you may found inside some of the teas you purchased from us. It's called o-buster or oxygen scavenger.
As you may know, the preservation of tea is all about "humidity". At the last stage of the tea processing, it is very important to make sure that the teas are properly dried. Normally, at the final stage of processing for oolongs, the tea will have about 3~5% water content, although some really experienced processors will be able to keep the water content level even lower.
During the final stage of oolong tea production some level of roasting or baking is done to further limit (and lower) the water content in the tea so that it can be packaged and kept without spoilage. In addition to vacuum sealing these oolong teas, we also insert an "o-buster" packet inside the vacuum sealed package to ensure that the tea remains dry and fresh. This little thing will help absorb the remaining oxygen inside the package, and therefore prevent the tea from the unwanted oxidation.
But here is a very important part and knowledge about this little thing. Once the package is opened, what should you do with the "o-buster" packet? Should I keep it inside? Or should I just throw it away? The best answer is to simply throw it away. This is because the "o-buster" packet will generate heat when it makes contact with oxygen, and it will continue do so until the oxygen is fully absorbed. After opening the tea bag, unless you have a vacuum sealing machine, it is impossible to separate the oxygen entirely in the air anymore. As a result unwanted heat will be continuously generate inside the tea bag, leading to loss of freshness due to over-heated tea. Additionally the tea once opened should be kept sealed or in an airtight container and stored in a cool dry place away from strong sunlight.