Q: Cleanroom Wipers: Where are irradiation dots located and what do they mean? 
A: Irradiation indicators (dots) are not an indication of sterility. They indicate that product has been exposed to irradiation. The color changes from yellow to red due to a shift in pH. Indicators are typically placed on the outer packaging (on the case) for inventory control purposes. Indicators can also be placed on inner packages. Under some conditions such as high heat, prolonged UV light, direct sunlight or exposure to alkaline conditions the irradiation indicators may turn orange or orange-yellow. Because of this they should not be depended upon to indicate sterility of the product. 
Q: How can I can be sure the wipers are sterile, if I can’t depend on an irradiation dot? 

A: A Certificate of Sterility (CoS) is available with each case of product and can be downloaded from our website here . The CoS lists the Item#, Product Name, Lot# and Expiration Date along with other valuable information. The CoS is the proof that the specified lot# has been irradiated at the required dose and validated sterile in accordance with procedures outlined in ANSI/AAMI/ISO 11137.
For further information
Please read the Technical Brief, “When It Has To Be Sterile”   There is a difference between Validated Sterile and Gamma Irradiated cleanroom wipers.