Answer to Question #9887 Submitted to "Ask the Experts"
Category: Security Screening
The following question was answered by an expert in the appropriate field:
Occasionally I receive packages at work (usually paper since I work for a company that makes paper coatings) that are marked "Checked by X-ray" or more recently a big red sticker that says "X-ray: Tick after X-Ray" with a check box.
Why do shipping companies need to notify recipients that a package has been x rayed or needs to be x rayed? Is there a difference between when a package has a large red "X-ray" sticker or a green "Inspected by X-ray" sticker?
There are two reasons for the stickers and one reason for the different colors.
The primary reason for the stickers even being on the packages is part of a general "consumer right-to-know" act passed by Congress in the 1980s. The main thought behind it was to provide more transparency/consumer information regarding hazardous materials and how they are used. It was really meant for such things as packaging on vegetables and fruits that pesticides were used or if you could be exposed to something as a result of the factory down the street, but impacted a lot more than that. The most important reason for you to know that your materials are being x rayed is in the event the product is sensitive to radiation (e.g., photographic film). In that case, whoever is shipping the product to you needs to label the shipment "Do not x ray."
The usual reason for different colors is the different uses of the radiation. In one case (red), sterilization of the product inside is implied. In the other case (green), smaller amounts of radiation were used just to take a look inside the package without having to open it. The latter is more a security item. It appears, though, that in the case you describe, both the red and the green simply mean the contents were looked at—not sterilized. If that is the case, it simply might be that the companies who do the screening are updating their labels and the different color just means that it's a newer version of the label.
Certified Medical Health Physicist